Liu Yongfu
The Vietnamese government, unable to confront Rivière with its own ramshackle army, enlisted the help of Liu Yongfu, whose well-trained and seasoned Black Flag soldiers were to prove a thorn in the side of the French. The Black Flags had already inflicted one humiliating defeat on a French force commanded by "lieutenant de vaisseau" Francis Garnier in 1873. Like Rivière in 1882, Garnier had exceeded his instructions and attempted to intervene militarily in northern Vietnam. Liu Yongfu had been called in by the Vietnamese government, and ended a remarkable series of French victories against the Vietnamese by defeating Garnier's small French force beneath the walls of Hanoi. Garnier was killed in this battle, and the French government later disavowed his expedition.