 Yang Yichen was considered to be honest and careful, with military leadership qualities, and Emperor Wen respected him.In 599, when Tujue's Bujia Khan Ashina Dianjue attacked, Yang Yichen was sent to face Tujue forces, and he repelled them.In 600, in conjunction with Shi Wansui (史萬歲) the Duke of Taiping, he dealt Ashina Dianjue a major defeat.