Yuwen Shu
In 609, Yang Yichen served as a general in the largely successful campaign against Tuyuhun. In 612, he also served in Emperor Yang's first campaign against Goguryeo, commanding part of the force under Yuwen Shu the Duke of Xu that aimed to penetrate deep into Goguryeo territory, against its capital Pyongyang. While Yang Yichen was personally successful, the campaign was itself a major failure, and as a result, Yang Yichen was removed from his post. However, Emperor Yang soon restored him, and in 613, when Emperor Yang launched a second campaign against Tuyuhun, Yang Yichen again served under Yuwen in an attempt to attack Pyongyang, but when news arrived that Yang Su's son Yang Xuangan had rebelled near the eastern capital Luoyang the campaign was abandoned. Afterwards, with much of Sui territory engulfed in agrarian rebellions, Yang Yichen was sent against the rebel leader Xiang Haiming (向海明), who had claimed imperial title near Chang'an, and Yang Yichen defeated Xiang.