Since the 19th century, Vietnam had been controlled by France as a protectorate (1883-1939) and then as a possession (1939-1945). Independence returned to the country when Ho Chi Minh proclaimed its independence with the declaration of the Democratic Republic of Vietnam in 1945.

The First Indochina War lasted from 1946 to 1954, as the French opposed the Vietnamese independence, and Ho Chi Minh led guerrilla warfare against the French. The war ended in the Vietnamese victory at Dien Bien Phu on May 7, 1954.

See the video below for more information of the Dien Bien Phu Battle.
An agreement was signed at Geneva on July 21, 1954, which provided a temporary division of the country between a communist-dominated north led by Ho Chi Minh and a U.S.-supported south led by Bao Dai. Both sides wanted a unified Vietnam, but Ho and his supporters wanted it modeled after other communist countries, while Bao and other supports wanted a Vietnam with close ties to the West.

In 1954, Bao Dai appointed Ngo Dinh Diem, a South Vietnamese politician, the prime minister of the State of Vietnam. In 1955, with the support of the U.S., Diem deposed Bao and established the Republic of Vietnam, declaring himself the president. After the election failed, the North Vietnam started to fight against the government by occupying portions of Laos to assist the Viet Cong, marking the beginning of the Second Indochina War, which is commonly known as the Vietnam War.