This dissertation examines responses of the National Council of Churches to moral, religious, political and socio-cultural issues surrounding American involvement in Vietnam 1965-1972. It does so by focusing upon NCC views of peace and justice as they were first developed within a process of cultural communication among ecumenical leaders in the NCC and constituent denominations; it then examines how these were aimed at persuading its denominational membership, grassroots Christians, and the government to a view of justice that the NCC believed would ensure domestic and international peace. Historical and ethnographic methods were used to research communication within the NCC, and then between the NCC, the general public and the government. They were also employed to investigate how the NCC functioned as an institutional expression of Protestant denominational pluralism regarding this war and probe why the government ignored views expressed by NCC and denominational leaders who were, in many respects, peers to the politicians and military personnel perpetuating it. The NCC felt compelled to address ethical issues raised by the war and tried to be a central prophetic voice in the debate over American policy and values throughout its duration. American ecumenical leaders often held enlightened, fact-based opinions on U.S. military involvement in Vietnam. Staffmembers in the NCC's Department of International Affairs had hoped to spark a transformation in the popularly held, government-reflected worldview and its correlating presuppositions relative to national security, justice and peace which they felt precipitated America's skewed Vietnam policies. But, because of the unpopularity of NCC socio-political stands at government and pew levels, as well as its leaders' sometimes elitist, ideologically exclusive attitudes, bureaucratic style, naive political strategies, and inattentiveness to the spiritual needs and opinions of grassroots Christians, the Council became alienated from parishioners and lost clout with the White House. In the NCC's response to the Vietnam War, one finds illustrated several precipitating causes of the mainline Protestantism' s "decline" of the 1970s.