Final answer:
The main reasons Vietnam and the US signed the Paris Peace Accords were Nixon's popular support, the military threat and guarantee from the US, and the official end of US force commitment to the war.
Step-by-step explanation:
The main reasons why Vietnam and the US signed the Paris Peace Accords were:
- Nixon's Vietnam policy and popular support: By the 1972 election, voters favored Nixon's Vietnam policy and he had popular support. This gave Nixon the leverage to negotiate a peace agreement.
- Military threat and guarantee: Nixon threatened to withdraw all aid and guaranteed to enforce the treaty militarily. This forced the North Vietnamese government to come to the negotiating table.
- Official end of US force commitment: The signing of the Paris Peace Accords marked the official end of US force commitment to the Vietnam War.