The Vietnam War began as a colonial conflict between the Viet Minh of Ho Chi Minh and the French administration that was seeking to regain control of Indochina after World War II. This conflict culminated in the French leaving Vietnam, the dividing of the country into two parts and the United States stepping in and replacing the French first with military advisors and then with active ground troops.
Vietnam had been part of French Indochina since the Treaty of Hue in 1884. During World War II, the Japanese assumed control of the region and ruled in cooperation with the French Vichy government. After WWII, the French sought to retake their colony, aided by the United States in its efforts to contain communism. After a major defeat to the Viet Minh in 1954, the French decided to withdraw from the country.
At the Geneva Peace Conference of 1954, Vietnam was temporarily divided at the 17th parallel into North Vietnam, under a communist government, and South Vietnam, under the control of Bao Dai, the former emperor of Vietnam. The United States attempted to fill the void left by the departing French by supplying finances, arms and advisors to the South Vietnamese in an attempt to protect South Vietnam from communism.
In August 1964 in the Gulf of Tonkin, North Vietnamese torpedo boats attacked U.S. destroyers. In retaliation, President Lyndon Johnson authorized air attacks on military targets in North Vietnam. With the Gulf of Tonkin Resolution, Congress authorized President Johnson to conduct military operations in Vietnam. In March 1965, he decided to send ground troops to Vietnam, and by the end of the year there were almost 200,000 American troops in the country.