A Study on the Background of the Reduction of the Tianbing army(天兵軍) and the Establishment of Taiyuan Fu(太原府) in the 11th Year of the Kaiyuan Era(開元) : Focusing on the Changes in the Relationship with the Türks(突厥) from the Wu Zetian(武則天) to the Xuan

This study focuses on how the government of the early Tang Dynasty used the Tianbing army(天兵軍) differently during various periods. As the Fubing military system(府兵制) was gradually dismantled, the government installed a number of troops along the border in its place. The Tianbing army was one of these forces, stationed at Taiyuan Fortress(太原城) and used as the core of the northern army. Although Wuzhou Dynasty(武周) did not take an offensive stance, through this, it was able to prevent the Türkic invasion of the south. The strategy of confronting the Türks, centered around the Tianbing army, was inherited by Zhongzong(中宗). Tianbing army, Datong army(大同軍) and Kelan army(岢嵐軍) in the area north of Taiyuan(太原), worked effectively to check the Türks. The Türks could no longer pressure the Tang from the eastern Ordos region and turned their attention to the western Ordos region. Xuanzong(玄宗) had the intention of taking control of Taiyuan in the process of competing with Empress Wei(韋皇后) and Princess Taiping(太平公主). He sent a loyal son-in-law to successfully establish influence over Taiyuan, which had been controlled by Empress Wei's faction. Xuanzong inherited the policies of Zhongzong and took an active stance in the campaign against the Türks. Just in time, when Kapgan Qaghan(默啜) died and a large number of barbarians(降胡) occurred, the Tang reorganized the northern military system around the Tianbing army. In the first half of the Kaiyuan era, the army near Taiyuan was commanded by the Tianbing army, and Taiyuan was defended by the Tianbing army, Datong Army, Hengye army(橫野軍), and Dawu army(大武軍). Bilge Qaghan(毗伽可汗), succeeding Kapgan Qaghan, maintained a policy of establishing peace with the Tang while consolidating internal affairs. In the 11th year of the Kaiyuan era, as Tang-Türkic relations entered a phase of reconciliation, the Tang government elevated Taiyuan to a Taiyuan Fu(太原府) and reduced the size of the Tianbing army. Through this, Xuanzong entrusted administrative authority over the Taiyuan region to Taiyuanyin(太原尹), while restricting military power, thus preventing the concentration of power in a local stronghold.