The Vietnam War lasted over 25 years starting in the 1950s when the United States began sending troops to Vietnam to fight against the spread of communism. Over the course of the war, almost 3 million US troops were deployed and it is estimated that over 2.5 million people were killed in total between both sides. While the US was worried about tensions caused by the war and cultural differences with Vietnam, their involvement eventually led to many internal conflicts in the US and widespread corruption in South Vietnam. The war ended in 1973 with a peace agreement and the withdrawal of US troops, and South Vietnam surrendered to the North in 1975 resulting in a reunified Vietnam.