Gao Pian
In 863, a major attack by Dali forces captured Annam District (安南, headquartered in modern Hanoi, Vietnam). Several successive Tang operations failed to make any headway against Dali forces. In 864, the chancellor Xiahou Zi recommended Gao Pian, who had by that point become a general of the imperial guards, to take over the Tang forces then under Zhang Yin () the military governor of Lingnan West Circuit (嶺南西道, headquartered in modern Nanning, Guangxi), to attack Annam. He was given the title of protector general of Annam.