Over the course of the Vietnam War , a large segment of the American population came to be opposed to U.S. involvement in South Vietnam . Public opinion steadily turned against the war following 1967 , and by 1970 only a third of Americans believed that the U.S. had not made a mistake by sending troops to fight in Vietnam . Anti-war activists organized massive protests like the Moratorium to End the War in Vietnam , which attracted over 600,000 protesters in various cities . Opinions concerning the war grew more polarized after the Selective Service System instituted a draft lottery in December 1969 . Some 30,000 young men fled to Canada to evade the draft between 1970 and 1973 . A wave of protests swept the country in reaction to the invasion of Cambodia . In what is known as the Kent State shootings , a protest at Kent State University ended in the deaths of four students after the Ohio Army National Guard opened fire on an unarmed crowd . The shootings increased tensions on other college campuses , and more than 75 colleges and universities were forced to shut down until the start of the next academic year . As the U.S. continually drew down the number of troops in Vietnam , the number of protests declined , especially after 1970
Kent State shootings
Kent State shootings
Presidency of Richard Nixon