This dissertation develops a history of soldiers' efforts to report war crimes over the course of the Vietnam War. Previous scholarship that addressed this issue largely dismissed GIs who alleged war crimes as political activists, dupes of the media, or individuals seeking forgiveness for their actions in combat. However, these three categories are insufficient to understand the motives leading troops to claim that they witnessed war crimes during their service in Southeast Asia. Nor do they account for how soldiers chose to make their allegations, or how their rationales or methods changed over time. By re-examining the historical record of GI involvement in the antiwar movement, media accounts of soldiers alleging war crimes, and declassified Department of Defense documents, this dissertation presents a new framework for understanding both how and why American soldiers reported atrocities. Soldiers adopted four primary venues when they alleged war crimes in Vietnam: their chain of command, the federal government, the media, or the antiwar movement. Generally, soldiers who remained convinced that the Army's hierarchy would properly investigate atrocity allegations reported atrocities through their local chains of command. As soldiers became increasingly disenchanted with the Army and the war, they chose more public venues to report war crimes. Soldiers who no longer believed that the Army, the federal government, or the press would act to address the problem of atrocities turned to the antiwar movement in an effort to educate the public about the conduct of the war, and its effects on both troops and Vietnamese noncombatants. This last group of soldiers naively hoped that just by publicizing the horrors of the war, the American public would call for it to end, forcing the Johnson and Nixon administrations to act. A key element affecting whether individuals chose to report atrocities was Seymour Hersh's explosive exposé of the My Lai Massacre in November 1969. Many soldiers who subsequently made war crimes allegations expressed their concerns that Lt. William Calley was a scapegoat selected by the Pentagon to placate the American public. They believed that commanding officers and policy-makers should accept the responsibility for American atrocities in Vietnam.