During the Second World War American soldiers participated in the discovery and liberation of many Nazi concentration camps. This monograph deals with their experience in the concentration camps, what they saw and what they did, and the long-term affects of their experience. The author has drawn heavily on the oral histories and personal papers of approximately 500 World War II veterans, and on military documents from the National Archives in Washington DC and the United States Army Military History Institute in Harrisburg, PA. Though substantial information was available at high levels in the American government, and to a lesser extent in the national newspapers, little was done to inform the GIs about the existence or purpose of the concentration camps. American soldiers were not prepared emotionally or psychologically for the enormous human suffering and degradation they witnessed. Viewing the camp atrocities and being exposed to the full extent of Nazi barbarism was a watershed experience for many American soldiers. Many developed an all-consuming hatred for Germans, particularly the SS, which occasionally culminated in a "take no more prisoners" approach to warfare. Conversely, American GIs responded to the malnourished and filthy survivors with great compassion. They were horrified by the condition of the survivors, but, with few exceptions, did not ignore or reject them. They assisted the survivors in every way possible, often grief-stricken that they could not do more. Liberators faced homecoming difficulties and adjustments common to veterans. However, they were often isolated and marginalized by civilians who refused to acknowledge the camps. Some veterans suffered for years with severe trauma symptoms (similar to PTSD criteria) related to the atrocities witnessed in the camps. Many veterans acknowledge that camp liberation had a long-term impact upon their life. Many attribute their involvement in politics, charitable organizations, and community affairs to lessons learned in the camps, lessons about justice, equality, and generosity. Further, almost all liberators support public Holocaust education and many participate themselves by giving witness testimony to school classes, and community and religious organizations. Jewish American liberators' experience was different; after seeing the camps, many developed a heightened sense of their Jewish identify and a deeper commitment to Israel. The eyewitness testimony of the liberators confirms that already provided by survivors and contributes an additional perspective on the Nazi concentration camp system.