On 16 February 253, Fei Yi was assassinated by Guo Xiu (郭脩), a defector from Wei, during a party on the first day of the Chinese New Year. After Fei Yi's death, Jiang Wei gained greater control over Shu's armed forces and could do as he wished. In the summer of that year, after learning of the Wu attack on Wei in the east, Jiang Wei led tens of thousands of Shu troops from Shiying (石營; northwest of present-day Xihe County, Gansu) to besiege Didao (狄道; around present-day Lintao County, Gansu).