The Black Flag Army (Chinese: Heiqi Jun) was a remnant of a bandit group who may have been former Taiping rebels that crossed the border from Guangxi province of China into Upper Tonkin, in the Empire of Annam (Vietnam) in 1865. They became known mainly for their fights against French forces in cooperation with both Vietnamese and Chinese authorities. The Black Flag Army is so named because of the preference of its commander, Liu Yongfu, for using black command flags.