Opposition to United States involvement in the Vietnam War began with demonstrations in 1964 against the escalating role of the U.S. military in the Vietnam War and grew into a broad social movement over the ensuing several years. This movement informed and helped shape the vigorous and polarizing debate, primarily in the United States, during the second half of the 1960s and early 1970s on how to end the war.
Many in the peace movement within the U.S. were students, mothers, or anti-establishment hippies. Opposition grew with participation by the African-American civil rights, women's liberation, and Chicano movements, and sectors of organized labor. Additional involvement came from many other groups, including educators, clergy, academics, journalists, lawyers, physicians (such as Benjamin Spock), and military veterans. Their actions consisted mainly of peaceful, nonviolent events; few events were deliberately provocative and violent. In some cases, police used violent tactics against peaceful demonstrators.