In early 1945, due to a combination of Japanese exploitation and poor weather, a famine broke out in Tonkin killing between 1 and 2 million people (out of a population of 10 million in the affected area). In March 1945, Japanese occupying forces ousted the French administration in Indochina as they had been holding secret talks with the Free French. Emperor Bảo Đại of the Nguyễn Dynasty nominally declared Vietnam independent, but the Japanese remained in occupation. Exploiting the administrative gap [8] that the internment of the French had created, the Viet Minh in March 1945 urged the population to ransack rice warehouses and refuse to pay their taxes. Between 75 and 100 warehouses were consequently raided. This rebellion against the effects of the famine and the authorities that were partially responsible for it bolstered the Viet Minh's popularity and they recruited many members during this period.

The Geneva Conference of 1954 ended France's colonial presence in Vietnam and partitioned the country into two states at the 17th parallel pending unification on the basis of internationally supervised free elections. Ngô Ðình Diệm, a former mandarin with a strong Catholic and Confucian background, was selected as Premier of the State of Vietnam by Bảo Đại. While Diệm was trying to settle the differences between the various armed militias in the South, Bảo Ðại was persuaded to reduce his power. Diệm used a referendum in 1955 to depose Bảo Đại and declare himself President of the Republic of Vietnam (South Vietnam). The Republic of Vietnam (RVN) was proclaimed in Saigon on October 26, 1955. The United States began to provide military and economic aid to the RVN, training RVN personnel, and sending U.S. advisors to assist in building the infrastructure for the new government.