 General Louis Brière de l'Isle, the commander-in-chief of French forces in Tonkin, was in Hanoi city at the time, and was planning to shift his headquarters to Hưng Hóa, to supervise a planned offensive against the Yunnan Army around Tuyên Quang.Brière de l'Isle concluded that the Red River Delta was in jeopardy and fired off a telegram on the evening of 28 March to the French government, warning that the Tonkin Expeditionary Corps faced disaster unless it was immediately reinforced