勤王運動
Vietnam had gradually become a French colony between 1859 and 1883. Initially, military resistance to French rule came through the Cần Vương movement led by Tôn Thất Thuyết and Phan Đình Phùng, which sought to install the boy Emperor Hàm Nghi at the head of an independent nation. However, with the death of Phùng in 1895, military opposition effectively ended. The only other notable incidents after this came in 1917 was the Thái Nguyên rebellion. The lack of militant activity changed in the late 1920s with the formation of the VNQDĐ, or Vietnamese Nationalist Party. The VNQDĐ attempted clandestine activities to undermine French rule, which resulted in French scrutiny of their activities. This led to their leadership group taking the risk of staging a large scale military attack in the Red River Delta in Northern Vietnam. It was only on 10 February 1931 that VNQDĐ could, in collaboration with civilian supporters, launch the Yên Bái mutiny, an uprising of Vietnamese soldiers in the French colonial army. Thus, Yên Bái was the first of the battles during the First Indochina War. Yên Bái and Thái Nguyên were key military posts of the Việt Minh, which were supplied with arms from China to fight the French during this War.