During the Cold War between the US and USSR after World War 2, the US became involved in the Vietnam War to prevent the spread of communism in Southeast Asia. The US feared that if Vietnam became communist it could lead other countries in the region to also become communist in a domino effect. Although the US initially only provided financial support, over the years its involvement transformed into sending soldiers to directly fight against communist forces in North Vietnam and the Viet Cong in South Vietnam. However, despite being a global superpower, the US was ultimately unable to win the Vietnam War, withdrawing from Saigon in 1975 in a humiliating defeat.