The Vietnam War started primarily because of the conflict between the communist North Vietnam and the anti-communist South Vietnam, with the United States getting involved to prevent the spread of communism in Southeast Asia. This involvement was rooted in Cold War fears, particularly the "domino theory," which suggested that if one country fell to communism, neighboring countries would follow. The war's origins also trace back to Vietnam's struggle for independence from French colonial rule and the division of Vietnam after the French defeat in 1954, which led to a civil conflict between the communist North led by Ho Chi Minh and the South supported by the US. The US escalated its military aid and presence in the early 1960s to support the South Vietnamese government and combat the communist insurgency from the North and the Viet Cong in the South. The Gulf of Tonkin incident in 1964 further intensified US involvement, allowing President Lyndon B. Johnson to escalate military action significantly. The broader context involves the Cold War geopolitical struggle between the Soviet Union, China, and the United States.