우문술
Emperor Wen died in 604, and Yang Hao's uncle Yang Guang took the throne as Emperor Yang. In 606, he created Yang Hao the Prince of Qin and Yang Zhan the Marquess of Jibei. By 613, Yang Hao was serving as the commander of the militia in Heyang Commandery (河陽, roughly modern Jiaozuo, Henan) when the general Yang Xuangan rebelled nearby. Emperor Yang, then at the front of a campaign against Goguryeo, sent the general Yuwen Shu back to Sui territory to attack Yang Xuangan, and Yuwen and Yang Hao exchanged letters, and they further met and joined forces against Yang Xuangan. However, after Yang Xuangan's rebellion was suppressed, Yang Hao was indicted for communicating with imperial officials—an act not allowed for imperial princes—and removed from his post.