临夏县
In 255, Shu general Jiang Wei decided to take advantage of the death of Wei regent Sima Shi by launching another campaign against Wei. The invasion force was one of the largest Jiang Wei had gathered in his Northern Expeditions, totalling at least 30,000 men, and included commanders such as Xiahou Ba and Zhang Yi. It is worth noting that both Xiahou Ba and Zhang Yi held higher appointments than Jiang Wei in administrating civil affairs, but Jiang Wei was in command instead because it was a military campaign. Xiahou Ba was a relative of the Shu imperial family (both of his nieces were married to Shu emperor Liu Shan). Zhang Yi was considered more senior than Jiang Wei and Xiahou Ba as he served Shu's founding emperor Liu Bei, while Jiang and Xiahou only joined Shu after Liu Bei's death. Between 18 September and 17 October, Jiang Wei's army took Fuhan (枹罕; located northeast of present-day Linxia County, Gansu), and advanced towards Didao (狄道; present-day Lintao County, Gansu).