When 1199 became the first Union to oppose the war in Vietnam, it did not represent the views of the leadership alone, but also large sections of the membership. That made it possible for 1199 Executive Secretary Moe Foner to play a leading role in organizing the 1965 Leadership Assembly for Peace in Chicago.

Prior to the Assembly, the Union placed an ad in the New York Times with the names of 1,268 members demanding the Johnson administration halt the bombing of Vietnam and seek an immediate cease fire. Each of the members whose names appeared contributed a dollar to help finance the ad.

Earlier, in July 1964, President Leon Davis had warned against the "aggressive and dangerous foreign policy we are pursuing in South Vietnam." And in 1965, the Union sent a telegram of opposition to President Johnson. Others took note. The progressive Negro American Labor Council adopted a World Peace Resolution against the war.

Throughout the late 1960s, leaders praised 1199 for its principled stance against the war. At the 1970 ceremonies dedicating the Union’s new headquarters, Congresswoman Bella Abzug, herself one of the pioneers in opposing America's involvement in Vietnam, praised 1199 for its opposition.

Said Dr. Martin Luther King, Jr. to an 1199 gathering weeks before his death on April 4, 1968: “I also believe that if all of labor were to follow your example of mobilizing and involving working people in the campaign to end the war in Vietnam, our nation would be much closer to a swift settlement of that immoral, unjust, and ill-considered war.”