2012 年 121 巻 7 号 p. 1247-1272
This article attempts not only to determine the institutional transition of the Northern Command (Beiya 北衙) system but also elucidate the interrelation between its development and coups d'etat that occurred during the early Tang period. The early Beiya, which also denominated the Four Imperial Armies of the North Gates (Beimen Sijun 北門四軍), can be divided into two regiments according to their role: the Garrison and the Imperial Guard. The Garrison, called the Flying Cavalry (Feiqi 飛騎), larger sized regiment of the Beiya, was established as the Seven Encampments of the Northern Command (Beiya Qiying 北衙七営), later transformed into the Left and Right Encampments (Zuoyou Zhunying 左右屯営) during the Taizong 太宗 era, then expanded and renamed the Left and Right Forest of Plumes Armies (Zuoyou Youlin Jun 左右羽林軍) during the Gaozong 高宗 era. They were permanently stationed at the North Gate, the Gate of the Black Tortoise (Xuanwu Men 玄武門), in order to defend the northern section of Chang'an Palace. Whereas the Garrison generally protected the palace and the Emperor within it, the Imperial Guards accompanied the Emperor whenever he left the palace for hunting or progresses. The Guards of the Yulin Jun developed from the Hundred Cavaliers (Baiqi 百騎) during the Taizong era, through the Thousand Cavaliers (Qianqi 千騎) during the reign of the Empress Wu, then the Left and Right Myriad Cavaliers (Zuoyou Wanqi 左右万騎) during the Zhongzong 中宗 era, and finally were promoted to the Left and Right Militant-as-Dragons Armies (Zuoyou Longwu jun 左右龍武軍) during the Xuanzong 玄宗 era. It should especially be noted that the development of the early Beiya virtually coincides with the rapid rise of the Imperial Guards, and ultimately the military strength of the Garrison and the Guards was completely reversed by the end of the early Tang period. Comparing the developmental stages of the Beiya mentioned above with the dates in which coups occurred, we can discern a close correlation between the military growth of the Beiya and these acts of rebellion. Whenever a coups d'etat was attempted, the Beiya was always made full use of in eliminating political opponents, and consequently, within the Beiya, the Garrison and the Guards gradually began to compete with each other. Although the Guards were little more than a small group within the Yulin Jun at the beginning, their utilization during coups triggered the regiment's expansion repeatedly, such that the more coups occurred, the more increases in personnel and military growth occurred only in the Guards. Therefore, during the early Tang period, to win a decisive victory in any coup d'etat, it became necessary for claimants to the throne not only to take control of the Beiya itself, but also to ally themselves with whatever was then the stronger of the two regiments inside the Beiya, the Garrison or the Guards.