Indochina had been a French colony from the late 19th century to the mid-20th century. When the Japanese invaded during World War II, the Viet Minh, a Communist-led common front under the leadership of Ho Chi Minh, opposed them with support from the United States, the Soviet Union and China. On V-J Day, 2 September, Ho Chi Minh proclaimed in Hanoi the establishment of the Democratic Republic of Vietnam (DRV). The DRV ruled as the only civil government in all of Vietnam for 20 days, after the abdication of Emperor Bảo Đại, who had governed under the Japanese rule. On 23 September 1945, French forces overthrew the local DRV government, and declared French authority restored. The French gradually retook control of Indochina. Following unsuccessful negotiations, the Viet Minh initiated an insurgency against French rule. Hostilities escalated into the First Indochina War.
By the 1950s, the conflict had become entwined with the Cold War. In January 1950, China and the Soviet Union recognized the Viet Minh's Democratic Republic of Vietnam, based in Hanoi, as the legitimate government of Vietnam. The following month the United States and Great Britain recognized the French-backed State of Vietnam in Saigon, led by former Emperor Bảo Đại, as the legitimate Vietnamese government. The outbreak of the Korean War in June 1950 convinced many Washington policymakers that the war in Indochina was an example of communist expansionism directed by the Soviet Union.
During the Battle of Dien Bien Phu (1954), U.S. carriers sailed to the Gulf of Tonkin and the U.S. conducted reconnaissance flights. France and the United States also discussed the use of three tactical nuclear weapons, although reports of how seriously this was considered and by whom are vague and contradictory. According to then-Vice President Richard Nixon, the Joint Chiefs of Staff drew up plans to use small tactical nuclear weapons to support the French. Nixon, a so-called "hawk" on Vietnam, suggested that the United States might have to "put American boys in". On 7 May 1954, the French garrison at Dien Bien Phu surrendered. The defeat marked the end of French military involvement in Indochina.