The Vietnam War, a protracted and divisive conflict lasting from the 1950s to 1975, pitted communist North Vietnam, supported by its communist allies, against South Vietnam, backed by the United States and other anti-communist nations. Fueled by the Cold War's ideological battle and the domino theory, the U.S. became increasingly involved, escalating military presence and engaging in intense combat. The war resulted in immense casualties, both military and civilian, widespread environmental damage, and significant social and political upheaval in both Vietnam and the United States. Ultimately, North Vietnam prevailed, unifying the country under communist rule, leaving a legacy of trauma, division, and enduring questions about the efficacy and morality of foreign intervention.