How did the United States become involved in the Vietnam War?

Prior to the end of World War II, the United States had been involved in Vietnam, which at the time was a part of French Indo-China, along with Laos and Cambodia.

The Vietnamese, led by General Giap, fought the French and defeated them at Dien Bien Phu. The Vietnamese were split into a communist North and a US-backed South at the 17th parallel, while Cambodia and Laos were declared neutral. The French assumed that after the Japanese were defeated in 1945, they would return to their previous position.

The US stepped up military aid, but it was ineffective; in 1963, Diem and his brother were killed in a CIA-backed military coup; shortly after Kennedy's death, US involvement intensified under Johnson; and in the South, the US-backed President Diem was supposed to hold elections but refused to do so.

Despite spending enormous sums of money and men, the Americans were unable to secure victory, and they withdrew in 1973. Two years later, communists had taken control of all of Vietnam, Cambodia, and Laos.

The United States became involved in the Vietnam War primarily due to its policy of containment during the Cold War. The U.S. aimed to prevent the spread of communism, fearing the "domino theory" where one country falling to communism might lead neighboring countries to follow suit. The U.S. initially provided financial aid to the French in their fight against communist forces in Vietnam. After the French were defeated in the Battle of Dien Bien Phu in 1954, the Geneva Accords divided Vietnam into North and South. The U.S. supported South Vietnam, sending military advisors and later combat troops to assist the South Vietnamese government against the communist Viet Cong and North Vietnamese forces. The Gulf of Tonkin incident in 1964 further escalated U.S. involvement, leading to increased military operations and troop deployments in Vietnam.