So in summary, the Tang dynasty's territory was too large, and its productivity and financial resources could not keep up, forcing it to decentralize power to the regional warlords. This model seemed effective and convenient in the early stages, but ultimately backfired on the Tang dynasty, leading to long-term turmoil after its decline.

In fact, given the productivity of an agricultural society, the territories of the Northern Song and Ming dynasties were roughly appropriate. Of course, the Northern Song lacked the Sixteen Prefectures of Yan and Yun, which increased rather than decreased defense costs.

It can be said that the map of the Central Plains was not perfect enough. From the Yanshan Mountains in Beijing to the Taihang Mountains in Shanxi and then to the Loess Plateau in northern Shaanxi, the defense line is not short, and the defense costs are relatively high. Building the Great Wall could only serve to delay the enemy, as the attacking side could easily break through at specific points.

免责声明：本文章仅代表作者个人观点，不代表本平台的立场和观点。本文章仅供信息分享，不构成对任何人的任何投资建议。用户与作者之间的任何争议，与本平台无关。如网页中刊载的文章或图片涉及侵权，请提供相关的权利证明和身份证明发送邮件到support@aicoin.com，本平台相关工作人员将会进行核查。