刘黑闼
In winter 621, Li Yi's You Prefecture was suffering from a famine. Gao agreed to supply You Prefecture with food, and when Li Yi sent the weaker of his men to Wei Province to save them from the famine, Gao treated them well. Li Yi was pleased, and he sent three thousand men with several hundred wagons and over 1,000 horses and donkeys to Wei Prefecture to transport food. Gao, however, turned against Li Yi and kept all of them, breaking off the relations with Li Yi and Tang Dynasty. He allied himself with the Eastern Turks to the north and Liu Heita to the south. He attacked Yi Prefecture (易州, part of modern Baoding, Hebei) but could not capture it. He, however, carried out pillaging raids against the prefectures under Li Yi's and other Tang generals' controls. In spring 623, he joined the Eastern Turks' Jiali Khan and Yuan Junzhang (), a general formally under Liu Wuzhou the Dingyang Khan, in attacking the Tang fortress at the seat of Yanmen County (present-day Daixian, Shanxi), but could not capture it. He continued to raid Tang prefectures for several years, often in conjunction with the Turks or Xi. In 623, he assisted Jiali Khan in sieging Mayi (present-day Shuozhou, Shanxi) and capturing it, although the khan soon returned Mayi to the Tang.