Military Communication Functions and Spatial Organization of Tang Dynasty Beacon Tower Architectural Heritage: A Case Study of the Circum-Tarim Region, Xinjiang, China

Tang dynasty beacon towers in Xinjiang’s circum-Tarim region constitute surviving architectural evidence of a frontier military communication system that supported regional governance and safeguarded the Silk Road. However, these beacon tower sites are generally small, severely weathered earthen structures whose military and heritage significance is difficult to interpret from individual remains alone. This study aims to reconstruct the military communication functions and spatial organization of Tang dynasty beacon tower architectural heritage in the circum-Tarim region. Specifically, this study seeks to quantify the recognizable distance of beacon-fire signals, identify visual connections among archaeological sites, and explain how visual signaling and road-based document transmission jointly maintained regional communication. First, key parameters were extracted from historical documents to calculate the maximum recognizable distance of beacon-fire signals. GIS intervisibility analysis was then conducted for 134 beacon towers and 54 associated city sites, and the results were integrated with military administrative jurisdictions, ancient transportation routes, city-site hierarchy, topography, and the “mapu” document-relay system. The analysis identified 262 effective intervisibility links among 139 sites. Among 101 adjacent site pairs without direct intervisibility, 62 routes may have maintained communication through road-based document transmission. The results indicate that the reconstructed system combined beacon-fire signaling with military document transmission and exhibited three principal spatial patterns: networked early warning in core oasis areas, linear transmission along the Silk Road, and point-based early warning near mountain passes. These arrangements linked the major military jurisdictions and directed information toward the Anxi Protectorate, the highest military and administrative center in the Western Regions. This study provides a viable GIS–historical approach for interpreting the functional and spatial organization of beacon tower architectural heritage, while offering a scientific basis for its integrated conservation and the interpretation of its military heritage values.