A war caused by French efforts to reassert control over its former colony of Indochina, following its exposure to Japanese forces during World War II. During that war, the Communist‐dominated Vietminh forces of Ho Chi Minh had developed into the main opposition to the Japanese. Upon Japanese defeat, Ho Chi Minh proclaimed the independent Democratic Republic of Vietnam. Other parts of Indochina, Laos and Cambodia, had also declared their independence. They were recognized by France on 6 March 1946 as autonomous states within the French Union.
Conflicts soon erupted between the Democratic Republic of Vietnam and French colonial authorities. After a dispute regarding rights to levy import duty, the French administration demanded the withdrawal of all Vietminh forces from the port of Haiphong. When this was not met, the French bombarded the town's Vietnamese quarter, killing over 6,000 civilians. The French failed to rally all non‐Communist forces behind the weak Bao Dai, while their tanks and superior equipment made little headway in jungle warfare. The confrontation soon proved to be beyond the French, who appealed to the USA for help. Impressed by the domino theory, the USA complied and bore 78 per cent of the military costs by 1954. By this time, the Vietminh, supported by a majority of the peasants, controlled virtually all the rural areas, while the French retained control of the cities. The French were by this time eager to withdraw, especially after losses at Dien Bien Phu. In the summer of 1954, they left behind a country divided along the 17th Parallel. French colonial forces had suffered almost 100,000 casualties in the war, though it is likely that losses among the Vietminh forces far exceeded this number.