Wei Yan
Yang Yi had disagreements with Wei Yan, a senior Shu general, and frequently quarrelled with him. Wei Yan often drew his sword and brandished it in front of Yang Yi; Yang Yi sobbed as tears rolled down his cheeks. Fei Yi then stepped in to stop them from fighting and managed to keep them under control until Zhuge Liang's death. Zhuge Liang was upset by the lack of harmony between Yang Yi and Wei Yan, but was unwilling to side with either of them because he appreciated the talents of both men. In 234, Yang Yi followed Zhuge Liang on another campaign against Cao Wei which led to the stalemate at the Battle of Wuzhang Plains. Zhuge Liang died of illness during the standoff, after which Yang Yi and the others ordered a retreat back to Shu. Around this time, relations between Yang Yi and Wei Yan deteriorated the point of conflict – they accused each other of treason and nearly started a civil war in Shu. The conflict concluded with the downfall and death of Wei Yan.