The ICP was formed in Hong Kong in 1930 from the amalgamation of the Vietnamese and the nascent Lao and Khmer communist groups, and it received its instructions from the Moscow-based Communist International (Comintern).
The Vietnamese communist movement began in Paris in 1920, when Ho Chi Minh, using the pseudonym Nguyen Ai Quoc, became a charter member of the French Communist Party. Two years later, Ho went to Moscow to study Marxist doctrine and then proceeded to Canton as a Comintern representative. While in China, he formed the Vietnamese Revolutionary Youth League, setting the stage for the formation of the Indochinese Communist Party in 1930. French repression of nationalists and communists forced some of the insurgents underground, and others escaped to China. Other dissidents were imprisoned, some emerging later to play important roles in the anti-colonial movement.
Ho Chi Minh was abroad at that time but was imprisoned later in Hong Kong by the British. He was released in 1933, and in 1936 a new French government released his compatriots who, at the outset of World War II, fled to China. There they were joined by Ho, who organized the Viet Minh-- purportedly a coalition of all anti-French Vietnamese groups. Official Vietnamese publications state that the Viet Minh was founded and led by the ICP.
Because a Vichy French administration in Vietnam during World War II cooperated with occupying Japanese forces, the Viet Minh's anti-French activity was also directed against the Japanese, and, for a short period, there was cooperation between the Viet Minh and Allied forces. When the French were ousted by the Japanese in March 1945, the Viet Minh began to move into the countryside from their base areas in the mountains of northern Vietnam. By the time Allied troops--Chinese in the north and British in the south--arrived to take the surrender of Japanese troops, the Viet Minh leaders had already announced the formation of a Democratic Republic of Vietnam (DRV) and on September 2, 1945, proclaimed Vietnam's independence.
Deep divisions between Vietnamese communist and non-communist nationalists soon began to surface, however, especially in the south, and with the arrival of Allied forces later in September, the DRV was forced to begin negotiations with the French on their future relationship. The difficult negotiations broke down in December 1946, and fighting began with a Viet Minh attack on the French in Hanoi.
A prolonged three-way struggle ensued among the Vietnamese communists (led by Ho Chi Minh), the French, and the Vietnamese nationalists (nominally led by Emperor Bao Dai).