The United States was concerned that if South Vietnam fell to communism, it would lead to a domino effect, with other countries in the region also falling to communism.

Operation Rolling Thunder was a sustained bombing campaign conducted by the United States against North Vietnam from 1965 to 1968.

The Spring Offensive, also known as the Ho Chi Minh Offensive, was a major offensive launched by North Vietnam in March 1975, which resulted in the fall of Saigon and the end of the Vietnam War.

According to the Department of Defense, 58,220 American soldiers died in the Vietnam War.

Estimates of the number of Vietnamese soldiers who died in the Vietnam War vary, but most sources agree that it was around 2 million.

The Paris Peace Accords were signed in January 1973 and called for a ceasefire, the withdrawal of American troops from Vietnam, and the release of American prisoners of war.

Richard Nixon was the president of the United States from 1969 to 1974. He oversaw the withdrawal of American troops from Vietnam, which was completed in 1973.

Ho Chi Minh was the leader of the North Vietnamese from 1945 until his death in 1969. He was a key figure in the Vietnamese independence movement and the Vietnam War.

William Westmoreland was the commander of the American military forces in Vietnam from 1964 to 1968. He was a key figure in the American military effort in the Vietnam War.

The Vietnam War Protest Movement was a social movement that opposed the Vietnam War. It was active from the early 1960s to the early 1970s.

CBS Reports: The My Lai Massacre was a documentary that aired on CBS in November 1969. It was the first major television program to report on the My Lai Massacre, which was a massacre of Vietnamese civilians by American soldiers in 1968.

Hugh Thompson was an American soldier who was awarded the Medal of Honor for his actions during the My Lai Massacre. He used his helicopter to rescue Vietnamese civilians who were being massacred by American soldiers.

William Calley was an American soldier who was convicted of murder for his role in the My Lai Massacre. He was sentenced to life in prison, but his sentence was later reduced to 20 years. He was released from prison in 1974.

The Deer Hunter is an American film that was released in 1978 and depicted the Vietnam War. It won five Academy Awards, including Best Picture and Best Director.

The Things They Carried is an American novel that was published in 1973 and depicted the Vietnam War. It won the Pulitzer Prize for Fiction in 1974.