Black Flag Army

The Black Flag Army (Chinese: ; pinyin: ; Vietnamese: Quân cờ đen) was a splinter remnant of a bandit group recruited largely from soldiers of ethnic Zhuang background, who crossed the border in 1865 from Guangxi, China into Upper Tonkin, then part of the Empire of Annam (Vietnam). Although brigands, they were known mainly for their fights against the invading French forces, who were then moving into Tonkin. With the sanction of both Vietnamese and Chinese authorities, the Black Flags joined the Vietnamese regular forces, stemming French encroachment beyond the Red River Delta. The Black Flag Army is so named because of the preference of its commander, Liu Yongfu, for using black command flags.

In 1857, Liu Yongfu (Vietnamese: Lưu Vĩnh Phúc), a Hakka soldier of fortune, commanded a group of about 200 men within a larger bandit group in Guangxi province headed by Huang Sihong (). He defected with his men to the band of Wu Yuanqing (Wu Yuan-ch'ing, ) under his own – black – flag. Liu organized a ceremony reminiscent of the tiandihui rituals and what became known as the Black Flag Army was born. The "army" operated as an independent unit under Wu Yuanqing and under his son and successor, Wu Yazhong (Wu Ya-chung, ) or Wu Hezhong. Although not part of the Taiping forces, both Wu Yuanqing and Wu Yazhong laid claim to be Taiping "princes".

After Qing forces crushed the Taiping Rebellion in 1864 in Nanking, the Qing army proceeded to destroy systematically the many armed bands of south-eastern provinces, particularly the band of Wu Yazhong in Guangxi. Hotly pursued, the desperate Wu Yazhong, with Liu and his Black Flag Army, crossed into Upper Tonkin in 1865.

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