December 19, 1946: The First Indochina War begins.
The “dirty war” was fought between France, its colonies and allies (most significantly the United States), and the State of Vietnam versus the communist Democratic Republic of Vietnam, which was supported by the Soviet Union and China, and led byHồ Chí Minh. It began as a rebellion against French occupying forces, which sought to retake its pre-World War II Southeast Asian colonies, including Vietnam, Laos, and Cambodia. What began as a small insurgency movement became full-blown war, which was stalemated and also highly unpopular in France, which was suffering from its own domestic problems.
Initially the United States sought to remain neutral because of its proclaimed opposition to imperialism, but as the Cold War congealed and fears of a communist takeover of the region grew, the U.S. found itself increasingly involved in the conflict. The communist People’s Republic of China, established partway through the war, could now provide more substantial aid through resources and weapons to rebel forces - although the United States provided more aid to France than China ever did to Vietnam. By the end of the war the United States was paying for 80% of the war’s costs. But whatever advantages in firepower and artillery the French possessed over their enemy, the Vietnamese made up for with an overwhelming superiority in manpower. At the end of the war, President Eisenhower introduced the idea of the domino theory in reference to communism in Indochina, the principle that would be used to justify the Second Indochina War (the Vietnam War):
…you have broader considerations that might follow what you would call the “falling domino” principle. You have a row of dominoes set up, you knock over the first one, and what will happen to the last one is the certainty that it will go over very quickly. So you could have a beginning of a disintegration that would have the most profound influences.
The war came to an end after the climactic battle at Dien Bien Phu, which culminated in a decisive victory for the Viet Minh over French forces. Soon after, the Geneva Conference began. The agreements of the conference temporarily split Vietnam into northern and southern regions, divided along the 17th parallel, to be unified in the future based on free and democratic elections, which were never held.