Vietnam was a very agricultural country, its key exports were coal, tin, and rubber.
Vietnam was very valuable to France.
During WW2 Vietnam was invaded by Japan. Japan stripped Vietnam of its natural resources. In fact, by 1945 almost 2 million Vietnamese people hadstarved to death.
The Vietminh (led by Ho Chi Minh) fought against Japanese control, and by 1945 the Vietminh controlled the majority of Vietnam
After WW2 french forces started fighting agaisnt the Vietminh. However neither side could gain the upper hand. This was embarassing for the French as a colonialpower was on par with one of their colonies.
In 1949 communists take over China, who then give help in the form of training and equipment to the Vietminh. This causes the Americans to worry about domino theory and believe the Vietminh are just puppets of China.
Truman gave $15million in military aid to the french to 'contain' communism.
In Dien Bien Phu 10,000 French troops were beaten by just 5000 Vietminh troops.
As a result of the defeat at Dien Bien Phu, France's president resigned. The leader who replaced him realised the war in Vietnam was really unpopular, so he supported peace talks.
In 1954 the Geneva agreement dictated that Vietnam would be split into North and South. The North was to be communist and led by Ho Chi Minh, and the South was to be capitalist and led by Diem.
Diem was a strong opposer of communism and had spent a lot of time in the USA.
The Geneva convention said that the Vietminh had to withdraw from South Vietnam.
The people could choose freely wether to live in the north or south.
Elections were meant to be held in July 1956.
Laos and Cambodia which were also French colonies were allowed to be independent countries thanks to the Geneva Convention.
Ho Chi Minh and Diem wanted a united Vietnam under their own rule.
Eisenhower who succeded Truman in 1953 was concerned about the growth of communism in Southeast Asia.