<human>:  Why did the anti-war movement start?
<bot>: The anti-war movement started in the 1960s as a protest against the Vietnam War. Many people opposed the war because they believed that the U.S. was not justified in fighting in Vietnam, and that the war was immoral. The movement gained momentum as more and more people became aware of the war, and as more and more people opposed the war. The movement ended with the end of the Vietnam War in the 1970s.