 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.