France began its conquest of Indochina in the late 1850s, and completed the pacification by 1893. The Treaty of Huế, concluded in 1884, formed the basis for French colonial rule in Vietnam for the next seven decades. In spite of military resistance, most notable by the Can Vuong of Phan Dinh Phung, by 1888, the area of the current-day nations of Cambodia and Vietnam was made into the colony of French Indochina (Laos was added later). Various Vietnamese opposition movements to the French rule existed during this period, such as the Viet Nam Quoc Dan Dang who staged the failed Yen Bai mutiny in 1930, but none were ultimately as successful as the Viet Minh common front, controlled by the Communist Party of Vietnam, founded in 1941 and funded by United States and Chinese Nationalist Party in its fight against Japanese occupation.

During World War II, the French were defeated by the Germans in 1940. For French Indochina, this meant that the colonial authorities became Vichy French, allies of the German-Italian Axis powers. In turn this meant that the French collaborated with the Japanese forces after their invasion of French Indochina during 1940. The French continued to run affairs in the colony, but ultimate power resided in the hands of the Japanese.

On May 1941, the Việt Minh was founded as a league for the independence from France. The Việt Minh also opposed Japanese occupation in 1945 for the same reason. The United States and Chinese national party supported them to weaken Japanese influence over Vietnam. However, they did not have enough power to fight actual battles at first. Ho Chi Minh was suspected of being a communist and jailed for a year by the Chinese national party.

Double occupation by France and Japan continued until the German forces were expelled from France and the French Indochina colonial authorities started holding secret talks with the Free French. Fearing that they could no longer trust the French authorities the Japanese army interned them all on March 9, 1945 and assumed direct control themselves[33] through their puppet state of the Empire of Vietnam under Bảo Đại.

During 1944–1945, a deep famine struck northern Vietnam due to a combination of poor weather and French/Japanese exploitation. According to Ho chi Minh's speech in August, 1 million people died of starvation (out of a population of 10 million in the affected area). Exploiting the administrative gap[35] that the internment of the French had created, the Viet Minh in March 1945 urged the population to ransack rice warehouses and refuse to pay their taxes. Between 75 and 100 warehouses were consequently raided. This rebellion against the effects of the famine and the authorities that were partially responsible for it bolstered the Viet Minh's popularity and they recruited many members during this period.

In August 1945, the Japanese had been defeated and surrendered unconditionally. In French Indochina this created a power vacuum as the French were still interned and the Japanese forces stood down. Into this vacuum, the Viet Minh entered and grasped power across Vietnam in the "August Revolution" (in large part supported by the Vietnamese population). After their defeat in the war, the Japanese Army gave weapons to the Vietnamese. To further help the nationalists, the Japanese kept Vichy French officials and military officers imprisoned for a month after the surrender. The Việt Minh had recruited more than 600 Japanese soldiers and given them roles to train or command Vietnamese soldiers.

On September 2, 1945, Ho Chi Minh, the leader of the Viet Minh, declared the independent Democratic Republic of Vietnam before a crowd of 500,000 in Hanoi. In an overture to the Americans, he began his speech by paraphrasing the United States Declaration of Independence: All men are created equal. The Creator has given us certain inviolable Rights: the right to Life, the right to be Free, and the right to achieve Happiness.

However, the major allied victors of World War II, the United Kingdom, the United States and the Soviet Union, all agreed that the area belonged to the French. As the French did not have the ships, weapons or soldiers to immediately retake Vietnam, the major powers came to an agreement that British troops would occupy the south while Nationalist Chinese forces would move in from the north. When the British landed they rearmed the interned French forces as well as parts of the surrendered Japanese forces to aid them in retaking southern Vietnam as they did not have enough troops to do this themselves.

Following the party line from Moscow, Ho Chi Minh initially attempted to negotiate with the French who were slowly re-establishing their control across the country. In January 1946, the Viet Minh won elections across central and northern Vietnam and began killing off opposition politicians. The French landed in Hanoi by March 1946 and in November of that year they ousted the Viet Minh from the city. Soon thereafter the Viet Minh began a guerrilla war against the French Union forces, beginning the First Indochina War.

The war spread to Laos and Cambodia where Communists organized the Pathet Lao and the Khmer Serai after the model of the Viet Minh. Globally, the Cold War began in earnest, which meant that the rapprochement that existed between the Western powers and the Soviet Union during World War II disintegrated. The Viet Minh fight was hampered by a lack of weapons; this situation changed by 1949 when the Chinese Communists had largely won the Chinese Civil War and were free to provide arms to their Vietnamese allies.