The historical process of the masonry city walls construction in China during 1st to 17th centuries AD.

Masonry city walls were common defense facilities in the cities of the Eurasian before the industrial revolution. However, they were not widespread in China until the Ming Dynasty (1368-1644). Limited in research methods, previous studies failed to make convincing arguments on this phenomenon. We collected, organized and analyzed relevant historical documents to reconstruct the spatio-temporal process of the construction of masonry walls from 1st to 17th century in China. We conducted a time series analysis primarily based on factors such as wars, garrisons, economy, and natural disasters. Analysis of the correlation among the construction of masonry walls and these factors provides insights into this process. From the 1st to 14th century, only 125 masonry city walls were built in China and the annual average number was below 0.1. While in the Ming Dynasty, a total of 1,493 masonry walls were built, with an annual average of 5.41. The construction activities in 1368-1456 spread throughout the country, but mainly appeared in the high-grade administrative cities and garrisons, as a result of the planned implementation of the central government. The construction activities in 1457-1644 had corresponding cluster areas during different periods, mainly at county-level. We found that the wall construction was stimulated by external factors such as wars and disasters. We believe that the mass construction of masonry walls in the Ming Dynasty is a phenomenon of cultural diffusion. The central government plan, the complex interactions between local governments and community, and the stimulation of external factors worked together to contribute to the diffusion of masonry city walls in the Ming Dynasty.