 When the general Yang Yichen was able to defeat several major rebels north of the Yellow River and forced many rebels to surrender, Emperor Yang was surprised at how many rebels surrendered—and Yu responded by stating, falsely, that Yang Yichen had been able to get "all" of them to surrender and that Emperor Yang no longer needed to worry.Subsequently, at Yu's instigation, probably because both Yu and Emperor Yang were apprehensive of Yang Yichen's responsibilities, Yang Yichen's forces were disbanded, and Yang Yichen himself was recalled to the imperial government around the new year 617 and ostensibly promoted but was detached from the army.Once Yang Yichen's campaigns terminated, the rebellions went unchecked.