The military conflict fought from 1955 to 1975 in Southeast Asia was the Vietnam War. This complex and contentious war primarily involved North Vietnam and its communist allies against South Vietnam, supported by the United States and other anti-communist nations. It stemmed from Cold War tensions and a desire to prevent the spread of communism in Asia. The war was marked by guerrilla warfare, significant civilian casualties, and widespread protests, particularly in the U.S. The conflict ultimately ended with the fall of Saigon in 1975, leading to the reunification of Vietnam under communist control and a lasting impact on American foreign policy and public perception of military engagement.