Xiao Yi, under attack from Xiao Ji, requested aid from Western Wei—in the form of an attack to Xiao Ji's rear, against Xiao Ji's home province Yi Province (modern central Sichuan).
Xiao Yi, facing a challenge from Xiao Ji, reached out to Western Wei for aid, suggesting a strategic attack on Xiao Ji's territory in the heart of Yi Province (now central Sichuan), where he had his roots.