President Lyndon Johnson, considered a liberal Democrat, escalated the Vietnam War, and Richard Nixon, a moderate Republican ended it. Johnson believed in the domino theory that if one country falls to Communism, then a neighboring country will be next. This was still during the Cold War and there was no profit motive on Johnson's part. Even though he was wrong and made things worse, he believed he was doing the right thing.

The U.S. didn't lose the Vietnam War. It was a draw, a tie. The U.S. formally ended its part in the Vietnam War when all sides signed the Paris Peace Accords on January 27, 1973. Following this the U.S. started removing its troops.

Vietnam was supposed to work on unification through peaceful means, but the North broke the deal and invaded the South. This means after the peace that the North started a civil war against the South. There was a provision that the U.S. could resume bombing the North if it broke the deal, but the Democratic Congress refused, and the South collapsed. So South Vietnam lost the civil war to North Vietnam.