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In the winter and spring of 1885 3,000 soldiers of the Black Flag Army served during the Siege of Tuyên Quang. At the Battle of Hòa Mộc (2 March 1885), the Black Flag Army inflicted heavy casualties on a French column marching to the relief of Tuyên Quang. French casualties at Hòa Mộc were 76 dead and 408 wounded, the highest casualty rate and the heaviest loss in a single day's fighting sustained by the French during the Sino-French War. Many French officers at Hòa Mộc said that the carnage was even worse than at Sơn Tây fifteen months earlier.