Front. Built Environ. Frontiers in Built Environment Front. Built Environ. 2297-3362 Frontiers Media S.A. 1764625 10.3389/fbuil.2026.1764625 Original Research Defense-connectivity synergy in the spatial evolution of China’s heritage corridor settlements: a multidimensional quantitative study of the Guangou section Xu and Zhao 10.3389/fbuil.2026.1764625 Xu Lingyu * Data curation Resources Formal Analysis Visualization Methodology Project administration Validation Software Writing - review and editing Investigation Supervision Funding acquisition Conceptualization Zhao Yun Resources Conceptualization Formal Analysis Visualization Validation Data curation Investigation Methodology Writing - original draft Supervision Software School of Architecture and Design, Beijing Jiaotong University, Beijing, China Correspondence: Lingyu Xu, lyxu@bjtu.edu.cn 17 02 2026 2026 12 1764625 10 12 2025 09 01 2026 19 01 2026 Copyright © 2026 Xu and Zhao. 2026 Xu and Zhao https://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Background

Heritage corridors represent complex cultural landscapes shaped by the historical interplay between military defense and transportation connectivity. However, the synergistic mechanisms behind this interplay remain underexplored.

 Methods

This study investigated these synergistic mechanisms by which military defense systems and transportation networks influenced the settlement spatial patterns within China’s heritage corridors, using the Guangou section of the Great Wall as a representative case. Through an interdisciplinary approach that integrated historical document analysis, field surveys, remote sensing interpretation, and historical GIS spatial analysis, we constructed a tripartite research framework of “element identification-spatial quantification-mechanism interpretation”. Specific analytical methods included: 1. Euclidean distance and viewshed analyses to assess the spatial control exerted by defense facilities; 2. Cost-path analysis and buffer zone analysis to reconstruct historical transportation networks; and 3. Spatial overlay and raster calculation to quantify defense-connectivity interactions.

 Results

Our findings revealed that settlement evolution underwent three distinct historical phases. Prior to the Ming Dynasty, settlements exhibited a dispersed, “mountain-water adjacent” distribution. During the Ming period, four distinctive settlement types emerged: High Defense-High Connectivity (HDHC) pass-courier station complexes, High Defense-Low Connectivity (HDLC) frontier military zones, Low Defense-High Connectivity (LDHC) plain waterway settlements, and Low Defense-Low Connectivity (LDLC) remote mountainous enclaves. Among these, the Guangou axial zone demonstrated an optimal defense-connectivity synergy model. In the Qing Dynasty phase, spatial configurations transitioned from “defensive control” to “connectivity empowerment”, characterized by “linear bead-like” and “planar networked” distribution patterns.

 Conclusion

This study innovatively proposed a theoretical framework and quantitative indicator system for “defense-connectivity” synergistic evolution. It developed a spatial analysis technical approach that integrated multi-source data fusion and multi-method integration, revealed the evolution patterns and mechanisms of different spatial types in the formation of heritage corridors, and established a spatial management methodology for the protection of linear cultural heritage. Our findings would not only deepen the understanding of the evolution patterns of defensive settlement systems, but also provide precise spatial management references for the “holistic protection” and “living inheritance” of the Great Wall National Cultural Park, offering a replicable analytical framework for global studies on similar heritage corridors.

 defense-connectivity driving mechanisms great wall military defense system historical transportation network reconstruction northwest Beijing Guangou quantitative analysis of historical evolution traditional settlements Youth Science Fund Project 10.13039/100014717 The author(s) declared that financial support was received for this work and/or its publication. The study was supported by the Youth Fund Project for Humanities and Social Sciences Research of the Ministry of Education of China (Grant No. 25YJCZH312). section-at-acceptance Transportation and Transit Systems Introduction

As a critical valley corridor linking the Beijing Plain and the Inner Mongolian Plateau, the Guangou area in northwest Beijing occupies a strategically significant position characterized by formidable terrain. This natural passage historically served as a primary route for nomadic incursions into Central China, making it a focal defensive zone for successive dynasties. This study quantitatively analyzed the “defense-connectivity driving mechanisms” through multidimensional spatial approaches, aiming to uncover the synergistic interactions between the Great Wall military system and transportation networks in shaping settlement distribution patterns, along with their historical differentiation (Yuan et al., 2024). By adopting a temporal framework from early civilizations to the early Qing Dynasty (prioritizing the Ming era), we integrated quantitative tools such as Geographic Information Systems (GIS) and Minimum Cumulative Resistance (MCR) models to establish a cross-period, multi-factor analytical framework. Current scholarship reflects a growing trend toward quantitative research on urban-rural settlements.

Tools such as ENVI, GIS, and space syntax have facilitated detailed analyses at macro, meso, and micro levels. Since the late 20th century, the proliferation of quantitative methods in settlement spatial studies has been accompanied by innovations in spatial information technologies, helping to elucidate morphological characteristics and evolutionary trajectories. Nevertheless, predominant approaches often lack data-driven transformation and fail to convert spatial relationships into quantifiable parameters (Geng, 2021). Most historical heritage studies in urban planning still rely heavily on archival analysis and basic GIS operations, without systematically quantifying historical data to interpret spatial dynamics. This research addresses this gap by operationalizing the historical spatial relationships of driving factors behind traditional settlements in Guangou. It transforms historical spatial correlations into analyzable datasets, thereby establishing verifiable quantitative correlations between settlement distributions and their driving forces.

Recent international research on historical settlement patterns has increasingly incorporated methodologies from GIS, landscape archaeology, and historical geography, with a particular focus on the influences of transportation routes, military defense systems, and natural environments on settlement distribution. This paper synthesized recent studies from international journals to explore the driving mechanisms behind settlement spatial patterns in Beijing’s northwest gully region.

The great wall’s military defense system and settlement distribution

Lin Y has examined the influence of the Ming Dynasty Great Wall’s military defense system on surrounding settlement layouts in the Journal of Geographical Sciences, revealing a hierarchical defense-settlement network formed by fortresses, beacon towers, and garrison-farming settlements along the Wall. The study utilized spatial statistics and buffer analysis to demonstrate that military requirements were a key determinant in settlement clustering. Similarly, Wang et al. in ISPRS Archives have employed high-resolution remote sensing data to analyze settlement site selection strategies along the Great Wall, proving that terrain visibility (viewshed analysis) and least-cost paths (LCP) could significantly affect spatial distribution patterns.

 Post roads and reconstruction of historical transportation networks

Historical transportation routes exert long-term effects on settlement organization. Sengupta, in Transactions in GIS, has used agent-based modeling (ABM) and LCP analysis to reconstruct travel routes from the Western Han Dynasty, noting that settlements along post roads typically demonstrate higher economic and social connectivity (Sengupta et al., 2023). This approach could be applied to the northwest gully region of Beijing to investigate how historical transportation networks shaped long-term settlement evolution.

 Gully landforms and settlement adaptation strategies

Gully systems play a crucial role in settlement sustainability. Zhang et al. in Geomorphology have analyzed the evolution of gully erosion in Northeast China’s black soil region from 1968 to 2018. As indicated by their results, land-use changes intensify gully erosion, consequently forcing settlements to relocate or adapt their layouts. This study provides a comparative case for examining settlement-environment interactions in Beijing’s northwest gully region (Zhang et al., 2024).

 Multidisciplinary approaches in settlement studies

Based on the spatial analysis of the Ming Great Wall’s Ji Town military settlement by Wang (2018), this study adopted a multi-technology integrated research approach. Specifically, it utilized GIS spatial statistics to reveal the hierarchical system of settlements and combined historical documents to verify spatial analysis results. Furthermore, it established methodological correspondence with the reconstruction of historical transportation networks by applying LCP and other methods. Notably, the terrain visibility analysis was applied to research the selection of garrison forts, which is methodologically analogous to the three-dimensional terrain visibility technology employed in this paper when discussing the visual correlation between the settlements in Beijing’s northwest valley and the Great Wall defense system. This mixed method, combining quantitative spatial analysis with historical and human geographical studies, provides a transferable paradigm for research on the spatial organization mechanism of military defense settlements.

 Materials and methods Study area Geographical and administrative context

The research area encompasses Guangou Town and Badaling Town, both township-level units traversed by the Guangou Valley. Administratively, these towns belong to the Changping District and Yanqing District of Beijing, respectively. Guangou Town is situated in the southeastern portion of Badaling Town. The macro-regional location of the Guangou area is shown in Figure 1. Historically, both towns served as critical military strongholds. The northern terminus of Guangou lies within Badaling Town, while its southern endpoint is located in Nankou Town (People’s Government of Changping District, 2020) (See Figure 2).

Macro-regional analysis.

Map of northeastern China highlighting historical features near Beijing, including Great Wall masonry structures, military settlements, the source of the Grand Canal, major cities, and the Yanshan and Taihang mountain ranges.

Micro-regional analysis.

Composite map with three inset satellite images showing the directions of Chadao, Guangou’s middle section, and Nankou, all connected with dashed lines to a topographic map of the Yanqing Small Basin, flanked by Yanshan and Taihang mountains, with a location inset of China and Beijing. Geographical location of Guangou

Guangou has historically been a contested strategic area, serving as a critical route connecting the Central Plains with the northern frontier. Stretching approximately 20 km in a northeast-southwest orientation, it constitutes the core route of the Jundu Pass, the eighth of the “Eight Passes” of the Taihang Mountains. Its northern end is Badaling, while the southern end is Nankou. The terrain is characterized by steep mountains on both sides and towering peaks, forming a perilous topography described as “two mountains flanking one valley.” Badaling, as the northern entrance to Guangou, stands at the highest elevation, approximately 600 m above sea level. Ancient inscriptions such as “Natural Barrier” and “Outer Defense of Juyong” highlight its military significance. The valley within Guangou is narrow, with the narrowest sections less than 100 m wide, making it easily defensible and difficult to attack. Historically, this terrain is pivotal in protecting Beijing from invasions by northern nomadic tribes. The current geographical features of Guangou are detailed in Figure 3.

Current geographical landscape of Guangou.

Three-panel photographic comparison features mountainous terrain, a winding road and buildings in the south pass, a reflective water body surrounded by mountains in the valley, and a broad view of a rugged landscape with vegetation and distant structures at the north entrance, all under clear skies. A millennium of military fortifications

The military significance of Nankou Town and Badaling Town dates back to the Warring States period. As the southern entrance of Guangou, Nankou Town guarded the northern edge of the North China Plain, serving as a frontline stronghold for Central Plains regimes against invasions by northern nomadic tribes. During the Ming Dynasty, the strategic importance of these two towns reached its peak. After Emperor Chengzu Zhu Di of the Ming Dynasty relocated the capital to Beijing, he established a defensive system centered around Juyong Pass, leveraging the strategic terrain of Guangou. Due to its location at the northern end of Guangou, Badaling Town served as the “ultimate barrier” of the Great Wall defense system. The Badaling section of the Great Wall was initially constructed in the 18th year of the Hongzhi reign of the Ming Dynasty (1505 AD), with inscriptions such as “Outer Defense of Juyong” and “Key to the North Gate” prominently highlighting its military significance. Although their military functions diminished during the Qing Dynasty, these two towns remained critical transportation hubs in northern Beijing, maintaining vital connections between the capital and the northwestern frontier. Refer to Figure 2 for details.

 Evolution of administrative divisions

The administrative history of Nankou Town is particularly distinctive. A village had already formed there during the Northern Wei Dynasty. In the Ming Dynasty, this town was jointly administered by Changpingzhou and Yanqingzhou, with areas south of the railway belonging to Changping and those north to Yanqing. In the first year of the Republic of China (1912), Nankou Town was established with Nankou Railway Station as its center, being a unique administrative division jointly governed by two counties. This arrangement continued until after 1949, when the town was incorporated into Changping District. In contrast, Badaling Town has long been under the jurisdiction of Yanqing. The Xibozi Commune was established in 1959, and the area was upgraded to a town in 1993 driven by the fame of the Badaling Great Wall. It has since gradually developed into the “Southern Gateway of Yanqing,” with cultural tourism at its core.

 Inheritance and elevation of great wall culture

Badaling Town has flourished due to the Great Wall, with its territory rich in Great Wall relics stretching 23.3 km, accounting for 90% of the brick-and-stone sections in Yanqing District. This includes the Badaling Great Wall, Shuiguan Great Wall, and others. In 1987, the Badaling Great Wall was inscribed as a UNESCO World Heritage site as a representative of the Great Wall of China, becoming a globally recognized cultural symbol. In contrast, Nankou Town centers around Juyong Pass, preserving historic sites such as the Cloud Platform and the Guqin Gorge, forming a north-south cultural and tourism axis with Badaling. The Great Wall sections in these towns are not only military relics; they have evolved into spiritual symbols of Chinese civilization, attracting poets and scholars across dynasties to compose verses in their praise. For instance, the Yuan Dynasty poet Hao Jing praised Juyong Pass with the lines: “Heavy gates and natural barriers guard Juyong, where the might of a hundred rivers and mountains grows ever more majestic.”

 Historical context of trade

Guangou is a rare natural route through the Yanshan Mountains, yet its towering peaks and deep valleys made travel difficult. Before the Ming Dynasty, its primary function was military defense, with fortifications such as Juyong Pass and Badaling built mainly to resist incursions by northern nomadic tribes. Even during wartime, small-scale border trade or smuggling activities persisted along the route, primarily involving the exchange of daily necessities. Official trade mechanisms such as the “Tea-Horse Trade” were predominantly conducted in more northwestern hubs like Zhangjiakou, with Guangou not serving as the main route. After the Ming and Qing dynasties established their capitals in Beijing, Guangou became a core segment of the official route connecting the capital with the northwest. The imperial courier route-the Beijing-Zhangjiakou Road-entered Guangou from Nankou, passed through Juyong Pass and Badaling, exited into Yanqing, and continued toward Zhangjiakou. Nankou Town, as the southern starting point of Guangou, developed into a crucial hub for material distribution and rest stops. Caravans would organize goods and hire pack animal teams here, leading to a proliferation of inns, stables, and warehouses along the route. As the southern starting point of Guangou, Nankou Town became a crucial hub for material distribution and rest stops. Caravans would organize goods and hire pack animal teams here, leading to a proliferation of inns, stables, and warehouses along the route. The Guangou section bustled with camel caravans and horse-drawn teams, transporting southern goods (such as tea, silk, cloth, and porcelain) northward, while bringing products from the Mongolian Plateau (such as fur, livestock, salt, and dairy) southward. By the mid-to-late Qing Dynasty, the Zhangjiakou-Kulun (now Ulaanbaatar) trade route flourished, with Guangou serving as a critical segment for traffic into and out of Beijing. This led to a significant increase in trade volume and stimulated the growth of commercial service economies in the towns and villages along the route.

 Analysis of driving elements for settlement spatial distribution in the Guangou area Hydrographic networks driving settlement distribution

The Guangou area is characterized by abundant and well-developed hydrographic networks, with water systems historically serving as crucial drivers for settlement formation and development. Most waterways in this region belong to the Beisha River (Edi torial Committee of Changping County Water Conservancy Records, 1992), a major tributary of the Wenyu River within the North Canal system. The Wenyu River originated from the convergence of multiple hot springs and was formally named during the Liao Dynasty (916–1125 CE) (Peng, 2025). Originating from the Jundu Mountains, this river system integrates several valleys including Guangou, Huyugou, Xiangtangou, and Xinglongkougou. Significantly, the main stem of the Wenyu River originates from the Guangou Valley. Multiple ancient records corroborate this hydrographic significance. For example, the Commentary on the Waterways Classic identifies it as “Shiyu Shui”, with Guangou as its primary source (Li, 2025). The Book of Han: Treatise on Geography documents: “In Jundu County, Shanggu Commandery, the Wenyu River flows eastward to Lu before joining the Gu River” (Ban, 2025). The current water systems have become relatively dry, with some sections repurposed as dams in Figure 4. TThe current state of the specific river is shown in Figure 4.

Current water systems in the study area.

Six photographs display segments of water and river systems with stone or concrete banks, dry or shallow streams, and surrounding bare trees or mountainous terrain during daylight, each labeled by river system and section.

These historical records could further confirm that canal networks were pivotal drivers for the spatially adaptive distribution of settlements in Guangou.

 Ancient postal routes driving settlement distribution

Courier stations, express relays, and postal relays constituted a three-tiered hierarchy that was functionally distinct yet operationally integrated, which were fundamental components of the imperial courier system. Within the research area, two primary types were present: courier stations and express relay posts. Both served as institutions for information transmission and operated under a stratified protocol. Routine documents were handled by Jidi Pu posts, which relied primarily on foot couriers. For urgent dispatches, horse or boat transport managed by formal stations was used. In regions with topographical constraints (such as high elevations or rugged terrain inaccessible to horse stations), the system employed a mutual reinforcement strategy: Jidi Pu posts would assume courier functions to fulfill the mandate of “establishing postal routes to convey commands”, thereby ensuring continuous information flow (Yang et al., 2024).

 Great Wall military defense system driving settlement spatial distribution The rise of the military defense system

According to records in the Xiguan Zhi, Juyong Pass has existed since ancient times, undergoing a prolonged evolution from the Spring and Autumn and Warring States periods to the Yuan Dynasty. Its defensive function has been closely intertwined with the surrounding settlements. Initially established by the Yan State as a barrier against the Donghu people, Juyong Pass later became a crucial inner defensive line of the Great Wall during the Qin and Han dynasties. During the Sui and Tang dynasties, it was revitalized as a key military stronghold in the Youji region of Hebei. Juyong Pass has consistently served as a crucial frontier fortress. During the Liao, Northern Song, and Jin periods, Juyong Pass became a strategically vital point for controlling Beijing, playing a significant role in shielding Yanjing. In the Yuan Dynasty, as its military importance diminished, the Guangou section of Juyong Pass transformed into a royal route. This shift allowed surrounding settlements to focus on production and daily life, highlighting the profound socio-economic impact of military changes on the Guangou region.

 Development of the military defense system

In the second year of the Hongwu reign (1369), when Xu Da was stationed in Beiping, shortly after the Ming Dynasty captured the Yuan capital, they promptly undertook the first large-scale construction of a fortress at a strategic location within the Guangou section of Juyong Pass. This initiative underscored the early Ming Dynasty’s emphasis on fortifying the defenses of the Guangou section of Juyong Pass, establishing it as the southern gateway of Juyong Pass and rapidly elevating its military significance. Subsequently, after Emperor Chengzu relocated the capital to Beijing in the 19th year of the Yongle reign (1421), the role of the entire Taihang Mountain range in guarding the capital became critically prominent, with Juyong Pass recognized as the “final line of defense for the capital.”

From the Tumu Crisis to the Gengxu Incident during the Jiajing reign, the court fully recognized the strategic importance of the Juyong Pass area and undertook extensive repairs to the fortress. By the Jiajing period, when the Changzhen Garrison was separated from the Jizhen Garrison, the defensive system of Juyong Pass in the northwest of the capital expanded to cover the entire region, reaching its maximum territorial extent.

Within the Guangou corridor, five fortresses are distributed from northwest to southeast: Chadao Fortress, Badaling Fortress, Shangguan Fortress, Juyong Pass Fortress, and Nankou Fortress. These form a defensive sequence, with all except Juyong Pass Fortress being classified as bastion towns. They were not constructed continuously; Juyong Pass was the earliest to be established, with its southern and northern entrances in use since the Jin Dynasty. The other four fortresses were deployed later. During the Yuan Dynasty, Shangguan Fortress, Juyong Pass, and Nankou Fortress already had defensive structures. During the Ming Dynasty, Nankou Fortress was built in the second year of the Yongle reign (1403) and reinforced in the third year of the Xuande reign (1428). The Shangguan Fortress of the Ming Dynasty occupied the original site of Juyong Pass. After Juyong Pass was relocated in the third year of the Jingtai reign (1452), Shangguan Fortress continued to utilize the existing defensive fortifications. The Badaling Fortress was initially constructed in the 18th year of the Hongzhi reign (1505), while the Chadao Fortress was first built in the ninth year of the Chenghua reign (1473). During this period, the locations of Shangguan and Badaling underwent adjustments. The current state of the five fortresses in Guangou is illustrated in Figure 5. Among them, Juyong Pass and Badaling have become famous tourist attractions, Chadao Fortress is a general scenic spot, Nankou Fortress remains inadequately protected, and Shangguan Fortress has almost no surviving relics, with only a small section of the Great Wall remaining. The Juyong Pass area features multiple layers of defensive barriers, as detailed in Table 1 and marked in Figure 5. Some of these historical structures remain preserved today, as shown in Figure 5.

Present conditions map of the five fortresses in Guangou.

Nine color photographs depict various parts and passes of the Great Wall of China and surrounding landscapes, including Nan Kou, Shang Guan, Ju Yong pass, Cha Dao, and Ba Daling, each labeled and credited to the author. Each photo shows distinctive views such as mountainous terrain, ancient stone structures and gates, walled pathways, and nearby settlements. All labels appear in blue boxes below the relevant images, with unique features of the wall or adjacent scenery visible in natural daylight.

Military settlements and strategic passes data inventory.

Level Settlement name Administrative jurisdiction Strategic type Defense urgency Garrison size (units)
Route fortress Juyong pass fortress Beiping regional command ​ Moderate 3
Bastion town Guangou fortress Subordinate to Juyong pass Inner pass Moderate 4
Shangguan fortress Inner pass Moderate 8
Badaling fortress Outer pass Moderate 3
Chadao fortress Outer pass Moderate 6
Lianghekou fortress Central route pass (Juyong pass-appointed officer) Outer pass Moderate 3
Shixiaguan fortress Northern route pass (Juyong pass-appointed officer) Outer pass Moderate 4
The transformation of the military defense system

After the late Jiajing period and into the Longqing era of the Ming Dynasty, the court continued to reinforce and repair the northern Great Wall fortifications. Renowned generals such as Qi Jiguang led the construction of hollow watchtowers, significantly enhancing the defensive capabilities of the Juyong Pass sector. By the late Ming Dynasty, as the frequency of military conflicts in the northwestern region of the capital decreased, threats to the Juyong Pass area gradually diminished, leading to a corresponding reduction in the military significance of the defensive zone (Li, 2021).

Historical records rarely document the construction of military settlements in the Juyong Pass area. Thereafter, the state ceased further construction of the Great Wall, and the military settlements in the Juyong Pass sector gradually evolved into ordinary villages. Economic and social activities in Nankou also shifted toward agriculture and commerce, with its military role gradually fading. The economic and social activities in Nankou gradually shifted toward agriculture and commerce, with its military role progressively fading. The area transformed into a region primarily focused on agricultural production and commercial circulation (Zhang et al., 2025).

 Data source and multidimensional database construction

This study established a multi-source, multi-temporal, and multi-dimensional thematic database to support a comprehensive spatiotemporal analysis of the Guangou heritage corridor. This database integrated historical documents, modern scholarly works, geospatial data, and policy documents, providing a robust foundation for quantitative spatial analysis.

Data sources and classification

Data collection encompassed four primary categories (See Table 2).

Data sources and classification.

Category Specific materials/Data types
Historical archives Commentary on the Waterways Classic; Xiguan Zhi; Sizhen Sankuan Zhi; Guangxu Changping Zhou Zhi; Yanqing Zhou Zhi; Yanqing Wei Zhilue; Changping Shanshui Ji; Changping Water Conservancy Records; Nankou Zhi
Academic works Zhongguo Changcheng Zhi; History of the Great Wall of China; Great Wall Studies; Actual Examination of the Ming Great Wall; Ming Dynasty Courier System; History of the Beijing-Hangzhou Grand Canal; History of Village Development in Beijing Suburbs
Cartographic data Beijing Historical Atlas Series; Jiubian Tushuo; Xuan Da Shanxi Sanzhen Tushuo; Chinese Great Wall Site Survey Report Collection; Ming Great Wall Atlas; China Railway Atlas
Survey reports Beijing Municipal Changping District Great Wall Resource Re-investigation and Protection Development Report
Policy and planning Great Wall Protection Ordinance; Great Wall Protection Master Plan; Great Wall National Cultural Park (Beijing Section) Construction Protection Plan; Beijing City Master Plan (2016–2035); Beijing Great Wall Cultural Belt Protection Development Plan; Beijing Traditional Village Protection Planning and Design Guide; Yanqing/Changping District Territorial Spatial Plans; Badaling Town/Nankou Town Territorial Spatial Plans
GIS data 1. GPS point data for great wall structures and settlements2. Administrative boundary vector data3. DEM4. Vector data for river systems5. Vector data for transportation networks
Historical documents and scholarly works

Core Historical Archives: Key primary sources were systematically collected, including: The Commentary on the Waterways Classic (《水经注》) for early hydrographic and human geography records; fortress gazetteers such as Xiguan Zhi (《西关志》) and Sizhen Sankuan Zhi (《四镇三关志》), which detail the Ming Dynasty military defense system; and local gazetteers such as Guangxu Changping Zhou Zhi (《光绪昌平州志》), and Yanqing Zhou Zhi (《延庆州志》) that provide comprehensive information on administrative evolution, topography, population, taxation, courier routes, and historical sites.

Academic Reference Works: Foundational scholarly works provided the theoretical and macro-historical context, including authoritative texts on the Great Wall system [e.g., Zhongguo Changcheng Zhi (《中国长城志》), Ming Changcheng Kaoshi (《明长城考实》)], the Ming courier system [e.g., Mingdai Yidi Zhidu (《明代驿递制度》)], the Grand Canal history [Jinghang Yunhe Shi (《京杭运河史》))], and regional settlement patterns [Beijing Jiaqu Cunluo Fazhan Shi (《北京郊区村落发展史》)].

 Cartographic and geospatial data

Historical and Thematic Atlases: Published historical map series, notably the Beijing Historical Atlas (《北京历史地图集》), provided a baseline for spatiotemporal reconstruction. Ming military atlases [e.g., Jiubian Tushuo (《九边图说》))] and modern Great Wall surveys [e.g., Zhongguo Changcheng Yiji Diaocha Baogaoji (《中国长城遗迹调查报告集》)] offered precise geographical information on defense structures.

GIS data: A core GIS database was built, including

Digital Elevation Model (DEM): High-resolution DEM data for terrain analysis, hydrological modeling, and viewshed analysis.

Vector Datasets: Precisely geolocated GPS data for Great Wall resources and traditional settlements; administrative boundaries for relevant districts and towns (Yanqing, Changping, Badaling, and Nankou); and vector data for both historical and contemporary river systems and transportation networks.

 Field surveys and policy documents

Specialized Survey Reports: The Beijing Changping District Great Wall Resource Re-investigation and Conservation Development Report provided authoritative, field-verified data on Great Wall relics, including precise surveys and condition assessments.

Regulations and Planning Documents: A hierarchical policy framework was constructed, encompassing regulations and plans from the national to the local level, including the national Great Wall Protection Ordinance, the Great Wall National Cultural Park (Beijing Section) Plan, municipal-level master plans [e.g., *Beijing City Master Plan (2016–2035)*], and district/town-level territorial spatial plans. These documents provided direct constraints and context for current and future land use.

 Data processing and GIS integration

All spatial data were processed and integrated using ArcGIS 10.7, which was selected for its comprehensive capabilities in data management, spatial analysis, and cartographic visualization. A unified WGS 1984 geographic coordinate system was applied to all datasets. Data processing consisted of the following key steps.

Settlement Distribution Data: Data were sourced from local government records and cross-referenced with local gazetteers (e.g., Changping Xian Zhi and Nankou Zhi) to verify the locations of historical and contemporary settlements. This process identified 95 traditional settlements, encompassing significant early sites such as the Xueshan Ruins, the Warring States-era Huyu Ancient City, and the Chadao settlement.

Great Wall Distribution Data: The dataset was constructed based on systematic surveys of Ming Great Wall resources, including walls, beacon towers, and fortresses. Fieldwork was conducted to verify the locations of strategically critical passes and fortresses (such as Juyong Pass, Badaling, and Chadao), thereby ensuring data accuracy against reports such as the Beijing Great Wall Resource Survey.

Canal and Hydrographic Data: Historical waterways (including the seven major gullies of Guangou, Huyugou, and Xiangtangou) were reconstructed through the integration of modern river GPS data with historical records from sources such as the History of the Beijing Grand Canal.

Postal Route Data: The Ming-era courier network was reconstructed through analysis of institutional studies (e.g., Ming Dynasty Courier System) and specialized research. This process enabled the geolocation of post stations and relay stops mentioned in historical documents.

Railway Data: Modern railway alignments were incorporated based on current GPS data and validated against historical transportation maps and local archival records.

Following individual layer preparation, all data were unified within a consistent coordinate system and integrated with the DEM. This process resulted in a comprehensive multi-element spatial database that served as the basis for all subsequent spatial analyses (Figure 6).

Gis spatial distribution of research data.

Topographic map with a color gradient showing elevation, locations of Ming-dynasty era settlements, military fortresses, postal stations, and hydrography in a region bounded by the Great Wall, with a detailed legend explaining each symbol and line type. Constitutive elements of defense-connectivity driving mechanisms

Based on the constructed database, this study systematically categorized and quantified the defensive and connectivity elements. The specific elements, corresponding spatial analysis methods, quantitative metrics, and their applicable historical periods are systematically summarized in Table 3.

Defense-connectivity driving mechanism research elements.

Element category Specific elements Spatial analysis methods Quantitative models and metrics Applicable period
Defense elements Great wall structures Euclidean distance analysis Great wall influence zone Ming dynasty and post-ming
Military settlements and passes Euclidean distance analysis Control index of military nodes Ming dynasty and post-ming
Topographic defensibility Minimum cumulative resistance model Terrain defensibility suitability index All periods
Connectivity elements Postal route network Cost-distance/path analysis Historical transportation accessibility index Ming-qing dynasties
Hydrographic corridors Buffer overlay analysis Riparian orientation index All periods

This study established a systematic classification of defensive and connectivity elements within the research area. The defensive elements focused on Great Wall structures, military settlements, and viewshed analysis. We employed buffer analysis and MCR modeling to quantify defense facility density, pass control efficacy, and topographic defensibility (Tomlin, 1999). These methods uncovered the military spatial logic underlying settlement clustering along defensive corridors, particularly during the Ming Dynasty and post-Ming periods. Connectivity elements included postal routes, hydrographic networks, canals, and railways. Through cost-distance analysis, we constructed metrics including historical transportation accessibility and riparian orientation index. This revealed settlement distribution patterns driven by transport network expansion and hydrological adaptation, with postal routes exerting a predominant influence on settlement layouts during the Ming-Qing period. Collectively, these reflected the spatio-temporal dynamics of “defense-dominated control” and “connectivity-enabled facilitation” (Niyogakiza and Liu, 2025).

This study synthesized data derived from a comprehensive literature review and field investigations to reconstruct the historical spatial patterns of traditional settlements, the Great Wall defenses, and canal networks along the Guangou corridor. All spatial data were systematically incorporated into a GIS for analytical modeling. The dataset encompassed 84 traditional settlements (Li, 2011), comprising archaeologically documented early settlements such as the Xueshan Ruins from prehistoric periods, the Warring States-era Huyu Ancient City, and the Spring-and-Autumn to Warring States-period Chadao Settlement. It also incorporated seven historically significant waterways (Guangou, Huyugou, Xiangtangou, Taowagou, Tanyugou, Huatagou, and Xinglongkou-gou), which were identified through archival research and hydrological fieldwork. The Ming Dynasty’s military infrastructure was particularly well-represented, featuring five strategic fortresses (Juyong Pass, Guangou, Chadao, Shangguan, and Badaling) along with secondary defensive nodes such as Lianghekou and Shixiaguan fortresses (Zhang, 2016), as well as the precise locations of mountain passes and administrative boundaries of Guangou and Badaling towns (Liu et al., 2025). Elevation data, settlement coordinates, and defensive structures were geospatially integrated to develop a multidimensional historical GIS model. This model elucidated the dynamic interplay between defensive configurations and transportation networks across different historical periods.

 Research methodology Buffer analysis

Purpose: To quantify spatial influence zones of linear/circular features (e.g., rivers and Great Wall segments).

Core Formula: B = p ∣ d p , L ≤ r where r denotes Buffer radius (e.g., 500 m for riparian zones) and L represents the target feature (e.g., canal network).

Application: Overlay with settlement data to assess the hydraulic guidance effects on habitation patterns.

Example: 78% of Ming Dynasty villages were located within 800 m of canal buffer zones.

 Euclidean distance analysis

Purpose: To evaluate straight-line spatial relationships between defense elements.

Core Formula: d = x 2 ‐ x 1 2 + y 2 ‐ y 1 2

Implementation involves calculating the distances from walls to garrisons to assess the efficiency of defensive layouts. Euclidean distance surfaces with a resolution of 30 m were generated to identify high-defense clusters (areas less than 1 km from multiple forts) and strategic gaps (regions over 3 km from the nearest wall segment).

 MCR model

Purpose: To simulate optimal paths considering terrain/land-use resistance.

Core Formula: C x = min L ∫ L R s · ds

The term C(x) represents the MCR value from a source point (such as a settlement or mountain pass) to a target location x, where L encompasses all potential paths between the source and target. The composite resistance value R(s) at spatial position s is derived from weighted factors including terrain slope, land-use type, and military defense priorities, while ds signifies the infinitesimal path segment distance.

 Cost-path analysis

Purpose: To derive LCP between nodes.

Core Formula: Path = arg   min L ∑ k = 1 n R k · d k where L denotes all potential paths from the origin to the destination, while Rk denotes the composite resistance value of the k-th grid cell along the path, and dk corresponds to the normalized traversal distance within the grid, typically scaled to the grid resolution.

 Viewshed analysis

Purpose: To evaluate intervisibility between an observer point and target locations, primarily utilizing DEMs to detect topographic obstructions.

This method is based on line-of-sight geometry.

Mathematical framework: For any two points A (x1, y1, z1) and B (x2, y2, z2), with the terrain profile represented by a continuous function z(t), the visibility condition is satisfied if and only if: z t = z 1 + t · z 2 ‐ z 1 , t ∈ 0 , 1

Research framework

This study examined defensive and connectivity elements across three historical phases: pre-Ming, Ming, and early Qing periods. As the Great Wall’s military defense system, constructed during the Ming Dynasty, became functionally obsolete in modern times and underwent no significant modifications during the Qing Dynasty, the defensive elements remained unchanged between these two periods. The analysis specifically focuses on Great Wall fortifications, military settlements, and strategic passes, applying Euclidean distance analysis to produce graded assessment maps (Liu, 2011).

For the Ming Dynasty’s postal routes, cost-distance analysis and the MCR model were employed to reconstruct transportation pathways linking military settlements and mountain passes. Historical records were cross-referenced to determine the locations of postal stations and emergency courier stops within and around the study area. Potential mountain trails were inferred from the spatial distribution of Ming settlements, enabling the reconstruction of the Ming transportation network. This network was subsequently extrapolated to the Qing period, with consideration for road continuity.

All temporal analyses incorporated terrain and hydrological corridors through MCR models and buffer overlay analysis to reveal how natural elements influenced spatial patterns. Spatial superposition was conducted by classifying defense and connectivity intensity levels across different periods, with graded raster maps used to illustrate their interactions and historical transitions. Ultimately, this approach established a multi-dimensional, cross-temporal research framework that integrated defense and mobility dynamics. Specific information regarding defensive and connectivity elements is presented in Table 3. The research conceptual framework is illustrated in Figure 7.

Quantitative analysis research framework.

Flowchart diagram with three columns titled Research Elements, Spatial Analysis, and Spatial Overlay, illustrating the process from identifying defensive and connectivity elements in different periods, through distance and resistance model analyses, to classifying regions by defense and connectivity strength. Results Spatial evaluation of defense element driving forces Pre-ming dynasty defense tier assessment and analysis Distribution of other pre-ming defense elements

Defense elements from the pre-Ming period, while spatially dispersed, held significant historical importance. Notable examples include Huyu Ancient City (Warring States period), Chadao and Juyong Pass (Spring and Autumn period), and Beitaipingzhuang (Yuan Dynasty military colony). Due to their scattered distribution and limited quantifiable impact, these features were incorporated into the defense-connectivity framework as discrete point elements. The spatial distribution of specific defensive element metrics is illustrated in Figure 8A.

(A) Pre-ming defense element distribution and (B) regional military viewshed analysis.

Two-panel figure showing spatial historical and archaeological data. Panel A maps military nodes, fortresses, ancient cities, and major settlements across a landscape, with color coding for different periods and a legend describing Yuan and pre-Yuan dynasty settlements, research boundaries, and hydrography. Panel B maps visibility analysis within the same area, using pink to indicate not visible and green to indicate visible regions, with the same research boundary shown. Both panels include a north-oriented compass rose and detailed legends. Viewshed analysis of pre-ming settlements

The topographic conditions of the Guangou area provided a fundamental natural basis for its historical development. By applying GIS slope analysis to the regional DEM, areas with steeper terrain gradients were identified as strategically advantageous due to their inherent defensibility, with slope magnitude directly correlating to defensive potential. This analysis produced a classified terrain defensibility map with three hierarchical tiers (Tier 1 = the highest defensibility; Tier 3 = lowest). This terrain defensibility classification served as the foundational metric for quantifying defensive characteristics across all historical periods.

Visibility constituted a critical factor influencing both military tactics and settlement patterns in the pre-Ming Dynasty, directly affecting battlefield outcomes and community security. Visibility analysis was conducted using GIS viewshed tools (see Equation 5) based on the regional DEM, with pre-Ming defense settlement locations designated as observation points. To simulate horizontal visibility ranges under historical conditions, sightlines were calculated at 1.6 m above ground level, approximating the eye level of an ancient individual. The results of the pre-Ming Dynasty viewshed analysis are presented in Figure 8B.

 Ming dynasty defense tier assessment and analysis Buffer analysis of the ming great wall linear structure’s spatial influence

Through historical documents and field surveys, the spatial distribution of the Ming Great Wall’s linear structure was reconstructed with GIS technology to develop vectorized spatial layers. Euclidean Distance (see Equation 2) analysis in GIS was employed to evaluate the wall’s zone of influence, creating a continuous distance distribution surface. Based on the defensive efficacy decay pattern, the influence area was classified into 5 tiers (Tie 5 = highest; Tie 1 = the lowest). Tier 5 represents the high-intensity defensive core zone closest to the wall, while Tiers 4 to 1 denote progressively expanding peripheral areas, demonstrating a clear gradient decline in defensive intensity with increasing distance. The results of the buffer analysis conducted on the defensive wall sections of the Ming Dynasty Great Wall are detailed in Figure 9B.

The process diagram of the comprehensive evaluation of the ming dynasty defensive capability. (A) Analysis of the visibility of military settlements and military defile. (B) Overall evaluation of the combined effect of the great wall’s defense system in space. (C) Comprehensive evaluation of ming dynasty defensive capability.

Panel A presents a map showing visibility zones of military settlements and fortresses near the Great Wall with green for visible and pink for not visible, including a legend identifying symbols. Panel B contains four smaller maps analyzing defense elements, buffer zones, and settlement distribution, each with a north arrow and legend, colors indicating evaluation grades from one to five. Panel C features a detailed map of the research area with graded defense evaluation overlaid, fortresses, and settlement positions, accompanied by a comprehensive legend and compass. Influence of ming military settlements and strategic passes

The spatial distribution of military settlements and passes was reconstituted using GIS. Due to hierarchical differences, with Juyong Pass Fortress at the top tier, the Five Fortresses of Guangou and other garrisons at mid-tier, and passes at the subordinate level, each defensive node was rated, separately. Four Euclidean Distance analyses were conducted for Juyong Pass Fortress, the Five Fortresses, other settlements, and passes, with their influence divided into five tiers (Tier 5 = strongest control). Spatial overlay synthesis visualized the combined defensive influence ranges (Wang, 2025). The results of the buffer analysis for the Ming Dynasty Great Wall military settlements and strategic passes are detailed in Figure 9B.

 Comprehensive ming defense influence intensity

The buffered influence zones of the Great Wall and the tiered influence rasters of settlements/passes were integrated using the GIS Raster Calculator, with higher weights assigned to the higher tiers. The resultant composite map was reclassified into 5 tiers, as revealed in Figure 9B.

Defense dominance radiated from Juyong Pass Fortress along the Guangou corridor, with stronger control observed in the southeastern sector.

Final overlay with the Great Wall alignment demonstrated that northern passes exerted greater defensive control than southern ones.

 Viewshed analysis of ming dynasty military settlements and military defile

During the Ming Dynasty’s military campaigns, visibility consideration critically influenced military settlement site selection, battlefield positioning, and garrison deployment at mountain passes, playing a decisive role in battle outcomes. Using the DEM of the study area, viewshed analysis was performed in GIS with the following parameters: 1. Observation points at military settlement and mountain pass garrison locations; 2. Viewing height set at approximately 1.6 m (simulating the eye level of ancient soldiers); 3. Viewing angle horizontal. The analysis indicated that site selection strategically balanced defensive concealment, with terrain-blocked (non-visible) areas backed by mountains for protection, as well as tactical visibility through maintaining extensive visible ranges for surveillance and strategic coordination. The detailed results of the pre-Ming viewshed analysis are presented in Figure 9A.

 Overall evaluation of the defense capabilities in the ming dynasty

The terrain defensibility assessment, the influence evaluation of military settlements and passes, and the viewshed analysis results were spatially overlaid in GIS. The detailed results of the Ming Dynasty defense analysis are presented in Figure 9C. These layers were reclassified into five defense tiers (Tier 1 = the lowest; Tier 5 = the highest), demonstrating that defensive strength radiated outward along the Guangou Corridor, particularly surrounding Juyong Pass Fortress. This pattern highlights Guangou’s critical military significance in Ming defense strategies.

 Spatial evaluation of connectivity element driving forces Pre-ming connectivity tier assessment and analysis Hydrographic buffer analysis

Through multi-dimensional data collection, various hydrological features were systematically coordinate-calibrated, vectorized, and assigned attributes. These features included: 1. Measured river networks from current topographic maps; 2. Historical river channels recorded in local chronicles and ancient military documents; and 3. Seasonal streams and dry riverbeds documented during field surveys. All elements were represented in GIS spatial data and classified into five grades (5 = highest to 1 = lowest). A buffer zone analysis (see Equation 1) of hydrological influence was conducted. Through overlay with settlement point layers, a quantitative analysis was performed to examine the impact of water systems on human settlement spatial patterns. This analysis elucidated how hydrological systems affected the distribution of settlements (Yin, 2025). The results of the hydrographic buffer analysis are detailed in Figure 10B.

Distribution of defensive elements before the ming dynasty and classification of water systems and buffer zones. (A) Ming defense element distribution. (B) Classification of water systems and buffer zones.

Map (A) displays Yuan and pre-Yuan Dynasty settlements, major post roads, temporary emperor residences, and reconstructed hydrography within a research boundary, with labeled sites Futuo, Sanbao, and Longhutai. Map (B) shows the same research region with hydrography and color-coded classification of water system buffering levels ranging from blue (level 1) to dark red (level 5). Both maps feature a north-oriented compass rose and detailed legends for reference. Distribution of other pre-ming connectivity elements

Beyond water systems, other pre-Ming connectivity elements were relatively scarce. Detailed information regarding connectivity elements is provided in Figure 10A. During the Jin Dynasty, Sanbao served as a crucial transportation node. In the Yuan Dynasty, Longhutai hosted an imperial traveling palace where emperors stopped during their journeys. Da Futuo and Xiao Futuo in the northern area functioned as relay post roads. However, these connectivity elements presented significant challenges for systematic analysis due to their sparse distribution across extended temporal ranges and insufficient data for quantitative assessment. Consequently, these pre-Ming connectivity elements were incorporated into the study of the defense-connectivity mechanism as point-based features (Ren et al., 2025).

 Connectivity level assessment and analysis of the ming dynasty Reconstruction and analysis of historical road networks in the ming dynasty

Based on historical records and relevant databases, the locations of post stations and emergency postal stops (such as Yulin Station, Yuhe Station, Changpingzhou General Stop, and Yanqingzhou General Stop) were reconstructed using GIS technology. By integrating historical documents and scholars’ reconstructions of Ming-Qing courier routes, we spatially reconstructed ancient post roads using GIS. The results indicated that the Ming-Qing post roads continued to extend north-south along the Guangou corridor.

Based on terrain elevation data, slope analysis was performed through GIS spatial analysis tools to calculate the slope values of various areas (Alberti, 2019). According to the impact of these slopes on military operations, they were classified into 5 categories: flat, gentle, moderate, steep, and very steep, providing foundational topographic data for subsequent analysis.

Subsequently, the MCR model (see Equation 3) was introduced, incorporating terrain slope and other factors influencing military movement. The MCR values of different areas were calculated and classified based on resistance levels, elucidating the difficulty and resistance of military operations across various regions.

Given the superior military significance of settlements compared to garrisoned passes, military settlements served as starting points. Using GIS cost-distance analysis tools, we calculated the cost distance from each military settlement to each pass (Valero et al., 2019). This measure was not a simple straight-line distance, but an actual traversal cost integrating various resistance factors.

To determine the optimal path from passes back to military settlements, cost-backtracking analysis was conducted. Starting from the passes and following the direction of LCP, the analysis traced back to each military settlement, pinpointing key nodes and specific routes along each path.

Finally, through integrating the results of cost-distance analysis and cost-backtracking analysis, we established optimized cost paths between military settlements and passes (See Figure 11) (Filet and Rossi, 2025). These cost paths visually represented the optimal routes between military settlements and passes, accounting for terrain, resistance, and other factors. The distances reflected the shortest and most efficient paths for military forces traveling from settlements to passes.

The process diagram of cost path generation. (A) The process diagram of cost path generation between military settlements and military defile. (B) The process diagram of cost path generation from Juyongguan fortress to military settlements and military defile.

Panel A contains four maps depicting gradient classification, cost-distance analysis, cost retroactive analysis, and cost path generation for military sites in a mountainous region, with a legend identifying fortresses, military defiles, and settlements, and a compass rose for orientation. Panel B shows a similar analysis with a different color scheme for paths and sites, using the same region and map structure, along with their own legend and compass rose.

Within the hierarchy of military settlements, Juyong Pass Fortress held a superior strategic status, followed by the Five Forts of Guangou, then other military outposts. All these fortified positions significantly outweighed the military importance of the garrisoned mountain passes. To reflect the dominant position of Juyong Pass in this defensive network, it was established as the analytical starting point. By incorporating pre-processed slope classification and resistance gradient data, we calculated cumulative cost-distance values from Juyong Pass Fortress to all subordinate military settlements and defensive passes.

Cost-backtracking analysis was performed to identify optimal movement corridors from peripheral passes back to core settlements. This process traced reverse pathways from each pass, following minimum-cost vectors to their affiliated military settlements, thereby pinpointing critical transit nodes and precise route trajectories. The integration of cost-distance and backtracking analyses resulted in a comprehensive LCP network connecting Juyong Pass’s command center with its supporting military installations and frontier choke points. The specific path outcomes and generation process are illustrated in Figure 11B.

Following the initial generation of cost paths (see Equation 4) between military settlements and strategic passes, we systematically integrated two candidate routes: one derived from LCP analysis and the other from traditional spatial distance calculations. Weighted matching of spatial coordinates, node distributions, and cost parameters between these routes were performed utilizing GIS-based path fusion algorithms (Loy, 2025), as indicated in Figure 12. This process eliminated redundant detours while preserving critical transit nodes, resulting in a preliminary composite path network. The merged pathways effectively represented both the hierarchical dominance relationships among military installations and the optimal routes for military operations. Special consideration was given to path optimization in the southern pass region, where the flat terrain, characterized by minimal elevation variation and sparse landmark features, required customized processing to identify the most strategically viable military transportation corridors.

Path merging optimization graph.

Map showing a mountainous region enclosed by a black outline, with key military sites marked: one black circle for Juyongguan Fortress, five red circles for Guangou Five Fortresses, purple squares for military defiles, orange squares for other military settlements, and a network of yellow lines representing merge routes. A compass rose is in the upper right, and a legend explains symbols. Analysis of postal routes and transportation networks during the ming-qing period

This study systematically integrated previously compiled Ming Dynasty postal routes and military transportation networks to construct a hierarchical, multi-layered traffic network system.

As the core infrastructure of military logistics, Ming postal routes served vital functions in intelligence transmission, material supply, and troop deployment. Their spatial distribution strictly adhered to the statutory framework of “one relay station every five li, one postal station every ten li”, with all Five Forts of Guangou strategically situated along these routes. Through integrating historical postal routes with military transport corridors, a composite traffic network was developed.

Given their primary military function during the Ming Dynasty, postal routes demonstrated exceptional historical transportation efficiency and strategic value. Due to their pivotal status within the historical traffic system, they were classified as Tier-1 routes in this network model. Auxiliary military paths, characterized by narrower widths and limited throughput capacity, were designated as Tier-2 routes. This established a dual-layered network architecture of “trunk postal arteries-auxiliary passages”. The specific transportation hierarchy and its spatial distribution are illustrated in Figure 13A.

Transportation routes and accessibility during the ming and qing dynasties. (A) The classification of historical post roads during the ming and qing dynasties. (B) Military settlements and military defile accessibility in the ming dynasty and the settlement map of the ming dynasty. (C) Map of transportation accessibility of post stations and emergency postal stop during the ming and qing dynasties.

Four-panel scientific map comparing postal stations, military settlements, and accessibility in a mountainous region, with colored overlays, symbols for forts and routes, legends explaining map features, and compass roses for orientation.

The study analyzed the transportation accessibility of Ming Dynasty military settlements and Military Defile and classified them into five accessibility grades (1 = lowest to 5 = highest). With the MCR model as the core framework, multiple data sources (including postal route classifications and terrain slope) were comprehensively evaluated. Cost-distance algorithms quantified actual travel time and costs between nodes, revealing distinct zones of transportation advantage along the Guangou corridor, southern passes, and northern passes, where accessibility levels were significantly higher. Topography notably affected accessibility patterns: plains exhibited greater accessibility than mountainous areas. Flat plains offered lower travel resistance, while mountains presented natural barriers (such as gorges and steep slopes) that severely constrained transport efficiency even with military access roads. GIS spatial analysis revealed how the radiating influence of military infrastructure enhanced accessibility, with Ming settlement patterns showing strong dependence on military transportation networks. These settlements concentrated along strategic corridors (such as the Guangou route and southern/northern passes), which functioned as crucial hubs connecting frontiers and hinterlands. These nodes served dual functions as material transfer/intelligence transmission centers and defensive nodes. This distribution pattern fundamentally reflected the Ming military’s strategic integration of transportation and defensive considerations, where major postal routes formed the backbone of a hierarchical network supplemented by secondary military paths adapted to local terrain constraints.

 Transportation accessibility of postal stations and emergency postal stops in relation to settlement patterns during the ming-qing period

Using a meticulously constructed high-precision spatial historical transportation network and terrain resistance surface, this study provided an in-depth analysis of the transportation accessibility of postal stations and emergency postal stops during the Ming-Qing period. These facilities were systematically categorized into five distinct accessibility grades (1 = lowest to 5 = highest).

The core framework employed a MCR model, integrating multi-source data (such as postal route classifications and terrain slope) to quantify actual travel time and costs between nodes using cost-distance algorithms.

The findings highlighted a notable transportation advantage zone along the Guangou corridor, where accessibility progressively extended outward from the central axis. The specific accessibility results are presented in Figure 13B. Notably, the southeastern and northwestern sections of the study area demonstrated higher accessibility levels (Grades 4–5) compared to the central region (Grades 2–3), forming a “dumbbell-shaped” spatial pattern. This variation arose from natural barriers (including gorges and steep slopes) present in the central mountainous zone, which significantly constrained movement efficiency. Conversely, the flat plains, characterized by minimal terrain resistance, enable broader accessibility coverage (Grades 4–5).

 Relationship with the ming dynasty settlement distribution

The analysis results of the Ming Dynasty settlement patterns and spatial accessibility are shown in Figure 13C. Spatial overlay analysis revealed a strong correlation between quantitative transportation accessibility and Ming military settlement patterns. Ming military settlements were strategically positioned at nodal points along transportation networks, closely aligning with reconstructed historical postal routes and military arteries. More than 95% of settlement sites were located along these postal routes, illustrating a distinct historical pattern of “prosperity along routes, abandonment with disconnection”. This distribution underscored the central role of transport corridors in military planning, with the most well-preserved settlement clusters situated along Tier-1 routes (such as the Guangou Ancient Courier Route). These findings highlighted the decisive influence of transportation infrastructure on the viability of military settlements.

This spatial dependency reflects the ancient “controlling planes through lines” defense strategy, where dominance over transportation corridors enabled regional military control and logistical superiority. Settlements functioned as materialized nodes within the network, serving both as military extensions of transportation functions and as empirical validation of the quantified accessibility results.

 Relationship with qing dynasty settlement distribution

The analysis results of Qing Dynasty settlement patterns and spatial accessibility are shown in Figure 13C. Analysis of Qing settlement patterns revealed a weakened correlation with transportation accessibility. While some dependency remained in the Guangou corridor and central mountainous zones (due to terrain constraints), most settlements migrated toward the southern plains, where the flat terrain ensured higher accessibility. This reorganization reflected the Qing dynasty’s reduced reliance on militarized corridor control, with economic and agricultural considerations increasingly influencing settlement distribution in accessible lowland regions.

 Evaluation and analysis of connectivity levels during the ming and qing dynasties

During the Ming and Qing dynasties, the connectivity along the Jingxi-Beiguangou corridor was influenced by the integrated effects of the postal road network and water systems. This study employed GIS spatial analysis techniques to conduct an overlay analysis between hydrological buffer zones and transportation accessibility maps of postal stations. Connectivity was classified into five ascending grades (1 = lowest to 5 = highest) based on the degree of spatial overlap and passage convenience.

The spatial overlay results are presented in Figure 14. The results revealed an inclined “王”-shaped spatial pattern in regional connectivity. Specifically, the areas along postal routes demonstrated significantly higher connectivity due to well-developed transportation networks. The southern passes benefited notably from proximity to waterways and the Grand Canal, showcasing enhanced connectivity through water transport. In contrast, the northern passes showed limited influence from hydrological factors. The Guanggou corridor emerged as a critical transportation bottleneck and the highest-grade connectivity node (Grade 5), leveraging the combined advantages of both postal routes and water systems, thereby underscoring its pivotal role in the regional transportation network.

Connectivity grade evaluation map of the ming and qing dynasties.

Map displaying postal network connectivity with colored zones indicating five levels of connectivity from high (dark red) to low (green), postal stations, emergency stops, Ming and Qing dynasty settlements, postal routes, local tracks, and research boundaries. Spatial overlay evolution analysis of defense-connectivity driving mechanism elements Pre-ming dynasty defense-connectivity driving mechanism

During the pre-Ming period, the defense and connectivity systems along the northwestern Beijing Guangou corridor remained in a developmental stage. Defensive elements primarily utilized natural terrain to create barriers, with only a few scattered physical defensive structures over centuries. This sporadic development hampered the formation of a systematic defensive network. In terms of connectivity, it was predominantly governed by hydrological systems; natural river channels facilitated the movement of people and goods, while formal roads and postal stations began to emerge gradually during the Yuan Dynasty.

This study employed GIS for a quantitative analysis of geographical elements from this period. The Euclidean distances to water systems and slope gradients were reclassified into five grades. Higher grades were assigned to areas with superior hydrological access and gentler slopes to reflect their connectivity potential. Subsequently, through spatial overlay of connectivity elements with defensive elements, this study categorized the region into four major zones: “high defense-high connectivity” (HDHC), “high defense-low connectivity” (HDLC), “low defense-high connectivity” (LDHC), and “low defense-low connectivity” (LDLC). The results are illustrated in Figure 15. Additionally, point-based defensive and connectivity elements were elevated by “+1” in their original grades to serve as a foundation for further analysis.

The combined diagram of defense and connectivity elements before the ming dynasty period.

Map showing the spatial distribution of Yuan Dynasty and Pre-Yuan settlements within a research boundary, categorized by defense and connectivity levels using four color-coded regions: blue, green, yellow, and red. Key locations labeled include Futu, Chadao, Sanbao, Original Lugong Pass, Huyu Ancient City, Beipaitanzhuang, and Longhutai. A legend clarifies settlement periods and each color's meaning. A compass rose and mile scale are in the upper right and bottom center, respectively.

The results indicated that the southern part of the study area exhibited higher connectivity advantages, while mountainous regions demonstrated stronger defensive characteristics. However, due to the limited number and dispersed distribution of pre-Ming elements (mostly manifesting as isolated point features), combined with historical factors (such as shifting political landscapes and warfare), there may be some deviation between the analytical results and historical realities. This deviation highlights the rudimentary and unstable nature of the region’s pre-Ming defense and connectivity systems, providing critical insights into their subsequent evolution.

 Spatial overlay analysis of the defense-connectivity driving mechanism in the ming and qing dynasties

The Ming Dynasty period represents a critical phase for analyzing the driving mechanisms of connectivity and defensive elements in the research area, characterized by distinct spatial transformations in these elements.

According to previous analyses, the defensive grade evaluation map and connectivity grade evaluation map were reclassified. For spatial grading, one was assigned values of “1, 2, 3, 4, 5”, while the other was graded as “10, 20, 30, 40, 50” (Openshaw et al., 1999). These were then overlaid as raster layers, with regions classified into high-grade zones (scoring above 2) and low-grade zones (other scores). Four categories were generated: HDHC, HDLC, LDHC, and LDLC. Higher values indicated stronger dominance of a single element. The resulting Ming Dynasty Defense-Connectivity Driven Zonation Map revealed distinct spatial differentiation along the Guangou corridor. The results are indicated in Figure 16.

Defense-connectivity driving mechanism spatial overlay diagram.

Colored map with a research boundary depicting varying defense and connectivity levels using a gradient from blue (low) to red (high). Green dots indicate Ming Dynasty settlements, and a legend explains color classifications.

HDHC Zone: This zone was characterized by a linear belt distribution extending outward from the Guangou core. This functionally integrated belt held critical military significance, with key installations (such as Juyong Pass and Badaling Fortress) densely distributed along this corridor. The corridor hosted numerous postal stations and emergency courier stops. It served dual roles as logistical hubs for intelligence and supply chains and frontline defensive strongholds, fully demonstrating the synergy between defense and connectivity.

LDHC Zone: This zone was concentrated in the southern plains and western mountains. The southern plains, traversed by canal tributaries and characterized by flat terrain, achieved exceptionally high connectivity. The southern pass area exhibited connectivity metrics far surpassing defensive values, resulting from the combined effects of hydrological systems and road networks.

HDLC Zone: This zone was primarily limited to Great Wall-adjacent sectors, reflecting prioritized fortification over transportation access.

During the Qing Dynasty, although the physical infrastructure of defense-connectivity remained unchanged, the Qing regime deprioritized the Ming Great Wall’s military importance. Consequently, no high-defense zones emerged in spatial analyses. Connectivity became the sole driving factor, eliminating the need for a multi-element overlay (Chen et al., 2020).

 Analysis of settlement distribution under the defense-connectivity mechanism

Prior to the Ming Dynasty (before 1368), settlement distribution exhibited strong dependence on natural features. Thirteen settlements were concentrated in HDHC areas, primarily utilizing rugged terrain to establish defense systems. Meanwhile, nine LDHC settlements were located along natural water systems, forming a “mountain-backed and water-adjacent” distribution pattern. During this period, few settlements appeared in LDLC areas, underscoring security as a primary condition for settlement survival.

During the Ming Dynasty, the settlement system underwent a significant transformation. Building upon the 13 settlements in HDHC areas, a well-defined hierarchical structure emerged: along the Guangou corridor, four level-6 core nodes and one level-5 node were established, surrounded by eight secondary nodes at levels 3–4. This transformation was facilitated by the advanced postal and garrison systems of the Ming Dynasty, which integrated military defense with transportation functions. Notably, a continuous belt-like settlement cluster formed along the Great Wall defense line. All high-defense areas (HDHC + HDLC) maintained strong connectivity, reflecting the strategic principle of “defense-transportation” coordinated development during the Ming period.

In the Qing Dynasty, the settlement system underwent fundamental reorganization. With the diminishing importance of military functions, connectivity became the primary determinant of settlement distribution: 26 highly connected settlements (at C-4/C-5 levels) emerged in plain areas, accounting for 62% of the total 42 settlements, while some former military fortresses from the Ming Dynasty transformed into commercial nodes. This spatial reorganization reflected a national strategic shift from military defense to economic development. Improved transportation networks enabled settlements to overcome previous geographical limitations, forming a denser and more balanced distribution across the plains.

The specific distribution data and visualization are presented in Table 4 and Figure 17. Comparative analysis results indicated that the settlement distribution patterns across these three periods illustrated an evolutionary trajectory from “point dispersion” to “strip clustering”, and finally to “network balance”. Correspondingly, the driving mechanisms transitioned from “natural defense dominance” to “military transportation collaboration” and ultimately to “economic factor driving”. This evolution process profoundly mirrors the historical progression of regional development from initial security assurance to efficiency optimization.

Statistics on the number of settlement evolutions in different periods.

Level The number of settlements in the pre-ming dynasty period Level The number of settlements in the ming dynasty Level The number of settlements in the qing dynasty
HDHC 4 HDHC HDHC-6 4 C-5 12
HDHC-5 1
HDHC-4 1
HDHC-3 4 C-4 14
HDHC-2 3
HDHC-1 0
HDLC 0 HDLC HDLC-2 0 C-3 14
HDLC-1 0
LDHC 6 LDHC LDHC-4 4
LDHC-3 4 C-2 2
LDHC-2 1
LDHC-1 0
LDLC 0 LDLC LDLC-5 1 C-1 0
LDLC-4 1
LDLC-3 3
LDLC-2 0
LDLC-1 0

HDHC, HDLC, LDHC, and LDLC, stand for High Defense and High Connectivity, High Defense and Low Connectivity, Low Defense and High Connectivity, and Low Defense and Low Connectivity, respectively. Here, “C” represents Connectivity.

Statistical chart of the number of settlement evolution.

Bar chart illustration summarizing settlement counts by type and historical period in three panels. Top panel shows Ming Dynasty settlements per cluster and type, with HDHC.6, HDHC.3, LDHC.4, and LDHC.3 reaching four settlements each. Bottom left panel compares pre-Ming settlements with four in HDHC and six in LDHC, with none in HDLC or LDLC. Bottom right panel displays Qing Dynasty settlements, highlighting c-4 and c-3 clusters with fourteen settlements, c-5 and c-4 with twelve each, and c-1 with none. Data types and units are clearly labeled. Summary of settlement spatial distribution evolution and classification

Across different historical periods (pre-Ming, Ming, Qing, and modern eras), the spatial distribution and site-selection mechanisms of settlements in the Guangou area have been dynamically shaped by the interplay of geographical environment, military defense, and transportation-economic factors, exhibiting distinct phased evolutionary characteristics. In summary, the adaptive distribution of settlements in the Guangou area has transitioned from “water system-dependent distribution” to “fortress-defense-oriented distribution,” and further to “trade and transport-oriented distribution.”

Pre-ming era: “water system-dependent” spatial distribution characteristics

Analysis of Historical Data: Historical records indicate that during this period, settlement locations were entirely guided by natural geography. Settlements were primarily distributed along the upper reaches of the Wenyu River system and in the gentle foothill plains, ensuring access to water for agriculture while utilizing mountain ridges and gullies as natural defensive barriers. This pattern formed two major settlement clusters: along the rivers and in the foothills.

Spatial Evaluation of Influencing Factors: Spatial analysis indicates that during this period, the interaction between “defense-connectivity” factors was relatively weak overall. Settlements were predominantly located in “high-connectivity” areas, specifically near water systems, with the spatial pattern exhibiting “point-like dispersion.” Natural conditions played an overwhelmingly dominant role in settlement site selection.

Settlements from the pre-Ming period exhibited a more pronounced spatial dependence on water systems, leading to the summary of their spatial characteristics as the “Water System-Dependent” pattern.

 Ming dynasty: “fortress-defense-oriented” spatial distribution characteristics

Analysis of Historical Data: Military records, border defense maps, and other historical sources confirm that with the comprehensive construction of the Ming Great Wall defense system, settlement layouts became highly coordinated with military needs. Settlements were densely clustered around strategic passes such as Juyong Pass and Badaling, as well as along walled fortifications, forming functionally specialized, militarily oriented, high-density settlement clusters.

Spatial Evaluation of Influencing Factors: During this period, the “defense-connectivity” interaction reached its “peak stage.” Settlements were highly concentrated in HDHC areas, such as around the “Five Fortresses of Guangou.” Spatially, they exhibited a “belt-like aggregation” pattern along defensive and postal routes, with a clearly defined hierarchical structure, where military and transportation functions synergistically reinforced each other.

The reliance of Ming Dynasty settlements on military installations was particularly pronounced, leading to the characterization of their spatial distribution as the “Fortress-Defense-Oriented” pattern.

 Post-qing dynasty: “trade and transport-oriented” spatial distribution characteristics

Analysis of Historical Data: Local gazetteers and immigration archives indicate that after the military function of the Great Wall diminished, the focus of regional development shifted toward resource utilization and economic exchange. Settlement scales expanded in the plains, while in mountainous areas, the influx of refugees for land reclamation and trade activities drove agricultural expansion into more favorable valleys. Site selection continued the tradition of proximity to water sources, but economic motivations became increasingly prominent.

Spatial Evaluation of Influencing Factors: The spatial pattern reveals that connectivity factors took precedence, while the overall interaction between “defense-connectivity” weakened. Settlements broke free from topographical constraints, expanding into plains and valleys with convenient transportation access, forming a more balanced “network-like distribution.” The role of economic and transportation factors became increasingly prominent.

Settlement distribution in the Qing Dynasty became more balanced, with economic and transportation trade growing increasingly prominent. Therefore, the spatial characteristics of settlements during this period are summarized as the “Trade and Transport-Oriented” pattern.

 Discussion

The findings of this study demonstrated a dynamic interplay between defense and connectivity factors in shaping the spatial distribution of traditional settlements in the Guangou area of northwest Beijing. Through a multidimensional quantitative approach incorporating GIS spatial analysis, historical document reconstruction, and spatial statistics, this study systematically decoded the spatiotemporal evolution of settlement patterns under varying historical military and transportation regimes. The key implications of our results are discussed below in relation to existing literature, methodological contributions, and broader theoretical frameworks.

Defense-connectivity synergy and historical settlement evolution

The analysis revealed that the settlement distribution in Guangou underwent three distinct evolutionary phases.

Pre-ming era: natural dominance phase

During this period, settlements were predominantly influenced by hydrographic networks and topographic defensibility, with minimal systematic military or transportation infrastructure. This observation aligns with studies on early settlement patterns in mountainous transition zones, where natural barriers and water accessibility served as key determinants. The clustering of settlements in HDHC zones reflects an adaptive strategy to balance security needs and resource availability.

 Ming dynasty: military-transportation integration phase

The construction of the Great Wall defense system and the establishment of a structured postal route network resulted in the formation of 4 distinct typological zones (HDHC, HDLC, LDHC, and LDLC). The HDHC belt along the Guangou corridor functioned as both a defensive stronghold and logistical artery, reinforcing the strategic concept of “controlling planes through lines”. This dual functionality is consistent with findings on Ming military settlements, where visibility analysis and LCP modeling have confirmed the strategic placement of garrisons along transportation routes.

 Qing dynasty: connectivity-driven restructuring phase

With the decline of military necessity, settlements gradually shifted towards areas of high connectivity, especially in the southern plains. This shift underscores the role of economic and administrative factors in post-military settlement evolution. A similar phenomenon was also observed in other historical contexts where demilitarization prompted urban and commercial expansion.

 Methodological innovations and contributions

This study advanced historical settlement research through the following contributions:

Quantifying Historical Spatial Relationships: The GIS-based framework transformed defense and connectivity elements into quantifiable indices, moving beyond traditional qualitative approaches. This methodological advancement facilitated reproducible analyses of historical spatial dynamics and effectively addressed a gap highlighted in the recent literature.

Integrating Multi-Source Data: Through synthesizing data from historical texts, field surveys, and remote sensing, a high-resolution reconstruction of the Ming-Qing postal routes and defensive layouts was achieved. The integration of LCP analysis with historical records offered a robust model for reconstructing lost transportation networks, a methodology that may be applicable to other historical corridors.

Dynamic Zonation Modeling: The classification of settlement zones provided a transferable framework for analyzing other frontier regions where defense and mobility intersect.

 Theoretical and practical implications

Military-Logistical Interdependence: The Ming case study illustrated that defense and connectivity operated not as opposing forces but as complementary systems. The clustering of settlements in HDHC zones underscored the strategic significance of locations that offer both protection and mobility, which is a principle that remains relevant to modern urban planning in conflict-prone areas.

Heritage Conservation Strategies: The transition from military to economic hubs during the Qing era indicated that preservation policies must account for functional shifts over time. For example, sites (such as Nankou) evolved from fortress into commercial nodes. Therefore, adaptive reuse strategies should reflect these historical layers.

Limitations and Future Directions: Although this study centers on the Ming-Qing transition, earlier dynasties also warrant deeper investigation to trace longer-term trends. Additionally, employing higher temporal resolution may uncover non-linear evolution patterns. In the reconstruction of historical elements, potential uncertainties (such as those related to ancient roads or waterways) may arise. To reduce such uncertainties and enhance data reliability, cross-verification using multiple sources and on-site investigations are required in later stages. Future research could also incorporate social factors to enhance the defense-connectivity model.

 Conclusion

This study developed a “defense-connectivity” evaluation system to systematically elucidate the historical evolution patterns of settlement distribution in northwestern Beijing. Prior to the Ming Dynasty, through multi-period grid overlay analysis, the research identified a functional transformation pattern in the Guangou area from “military dominance” to “transportation empowerment”. During the pre-Ming era, the spatial distribution of settlements was primarily influenced by natural elements (such as water systems and topography). Defense and connectivity elements exhibited scattered, point-like distributions, lacking a systematic driving force. By the Ming Dynasty, with the enhancements of the Great Wall defense system and the expansion of the post road network, the synergistic effect of defense and connectivity elements reached its peak. In this period, four typical areas were generated: HDHC, HDLC, LDHC, and LDLC. The Guangou axis became the core area of HDHC, owing to its dual roles of Great Wall fortifications and post road channels. This validated the military geographical concept of “controlling the area by controlling the line”. Since the Qing Dynasty, the defensive function of the Great Wall has diminished, and regional functions have shifted to a “high connectivity-low defense” pattern, illustrating a transition from military logic to economic logic.

This study demonstrated how the spatial organization of traditional settlements in Guangou was shaped by the dynamic interplay between defensive needs and transportation efficiency across historical periods. The methodological integration of GIS, historical geography, and quantitative spatial analysis offers a replicable model for examining settlement evolution in other geographically constrained regions of strategic importance. These findings not only contribute to academic debates on historical settlement patterns but also provide novel insights for cultural heritage management, highlighting the importance of preserving both military and logistical landscapes as interconnected systems.

Future research directions

Settlement Transformation and Functional Evolution in Post-Military Contexts: Future research should develop detailed case studies examining how Ming Dynasty garrison settlements adapted their spatial layouts and socioeconomic functions during the Qing Dynasty’s demilitarization. This should encompass systematic analysis of architectural modifications, land-use changes, and community reorganization patterns to understand the mechanisms underlying the military-to-civilian transition. Additionally, it is important to develop predictive models to identify the settlement characteristics that most significantly influence successful post-military adaptation.

Advanced Reconstruction and Simulation of Historical Transportation Networks: Improvements to existing LCP algorithms are necessary through the incorporation of time-dependent variables to generate more accurate historical route models. Future research could employ ABM to simulate traveler decision-making processes along reconstructed postal routes and mountain passes. These models should be validated through cross-comparison with newly discovered archaeological evidence of road remnants and locations (Cai et al., 2025). In the field of historical and cultural heritage conservation, integrating digital twin technology stands as one of the most promising directions today. It not only enables precise documentation of the current state but also simulates changes, predicts risks, and facilitates preventive conservation.

Holistic Conservation Frameworks for Defense-Connectivity Heritage Systems: There is a pressing need to develop integrated evaluation matrices that assess both the defensive and connective values of heritage sites within their historical operational contexts. “Heritage corridor” protection strategies should be proposed, emphasizing the functional relationships between Great Wall fortifications, transportation nodes, and supporting settlements. Furthermore, developing digital twin technologies would enable the visualization and analysis of dynamic interactions between military, logistical, and settlement elements across different historical periods.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

 Author contributions

LX: Data curation, Resources, Formal Analysis, Visualization, Methodology, Project administration, Validation, Software, Writing – review and editing, Investigation, Supervision, Funding acquisition, Conceptualization. YZ: Resources, Conceptualization, Formal Analysis, Visualization, Validation, Data curation, Investigation, Methodology, Writing – original draft, Supervision, Software.

 Acknowledgements

The author sincerely thanks the relevant government departments of Nankou Town and Badaling Town, as well as the village committee and villagers of Nankou Village for their support for this project.

 Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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 Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fbuil.2026.1764625/full#supplementary-material

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Edited by: Yuming Lin, Tsinghua University, China

Reviewed by: Dan Xie, Hebei University of Technology, China

Padma Sundar Maharjan, Tianjin University, China