Liu Heita
Su Dingfang later followed the rebel ruler Dou Jiande the Prince of Xia, and he was particularly favored by Dou's major general Gao Yaxian (), who treated him like a son. After Dou was defeated and captured by the Tang Dynasty general Li Shimin the Prince of Qin (the later Emperor Taizong) in 621, Xia domain was initially taken over by Tang, but Gao and a number of other former Xia generals rose later in the year, supporting the Xia general Liu Heita as the Prince of Handong, and Su served Liu in this campaign of resistance as well. After Gao's death in battle in 622, followed by Liu's defeat by Tang's crown prince Li Jiancheng (Li Shimin's older brother) in 623, Su returned to his home territory.