The United States became involved in the Vietnam War in the 1950s to prevent the spread of communism in Southeast Asia, as part of the broader Cold War struggle against the Soviet Union and its allies. The US initially provided military and financial aid to the French colonial government to fight against the communist-led Viet Minh independence movement. After the French were defeated at the Battle of Dien Bien Phu in 1954, the US became more directly involved in the conflict, sending its own troops and supporting the anti-communist regime in South Vietnam. The US escalation of the war in the 1960s led to a significant increase in American casualties and widespread opposition to the war both within the US and internationally. The war ended in 1975 with the communist victory and the reunification of Vietnam under a communist government.