Studies in Medieval Chinese Siegecraft: The Siege of Yü-pi, A.D. 546

North China in a.d. 546 was the scene of a contest between two men, de facto rulers of the fractions of Northern Wei which had held the entire area for over one hundred fifty years but had been split in the middle of the previous decade. One of the two men, Kao Huan,^b headed the state called Eastern Wei, in Shansi and Honan, which became the dynasty of Northern Chʻi under his descendants. The other, Yü-wen Tʻai,^e ruled Western Wei, in Shensi, later to become Northern Chou. The ensuing half-century witnessed the final victory of Northern Chou over Northern Chʻi, the usurpation of Northern Chou by the founder of the Sui dynasty, and Sui's destruction of the last of the Southern Dynasties to unify all of China and usher in the era of Tʻang.