According to Qing historical records, Hoang Sung Anh, a member of a group of the Tiandihui (Heaven and Earth Society) led by the father and son Ngo Lang Van and Ngo Con, who was pursued by the Qing army, took the remnants of his troops to Vietnam to shelter and loot along the Vietnam-China border. In 1869, Ngo Con was killed by the Nguyen Dynasty's army, but the remnants of those Chinese bandits still continued harassing and pillaging the areas along Vietnam-China border, which made the coalition troops of both countries have to strenuously suppress them, until in 1875 Hoang Sung Anh was killed in Tuyen Quang by the Nguyen dynasty'sarmy. The constant harassment of Chinese bandit troops had caused great losses to both countries, especially Vietnam, which suffered constant hostilities leading to military hardship in suppressing them and afflicted situation of people
as a result, the Nguyen dynasty could not mobilize entire Vietnamese combat troops to cope with the invasion of the French.