Murong Fuyun
Starting 622, Murong Fuyun, apparently under the advice of his strategist the Prince of Tianzhu, began frequent pillaging attacks on Tang's prefectures bordering Tuyuhun, making several attacks per year. The attacks continued throughout the rest of Emperor Gaozu's reign, up to 626 (when he was forced to abdicate in favor of his son Li Shimin (as Emperor Taizong)).