[Introduction] An internal history of the United States government's Nazi-hunting operation provides gripping new evidence about some of the most notorious Nazi cases of the last three decades. The Justice Department kept the 600-page report secret for the last four years, releasing a heavily redacted version last month to a private research group that sued to force its release. A complete version was obtained by The New York Times. [From the document] In the 1970s, the public was shocked to leam that some Nazi persecutors had emigrated to the United States. There were calls for their expulsion and legislation was passed to facilitate their deportation. OSI was created in 1979 to handle the caseload. The Office of Special Investigations (OSI) is often referred to as the government's Nazi-hunting" organization. While the cases and projects are individually fascinating, this report was not written simply to recount a series of unrelated but interesting undertakings. It is designed to serve as a teaching and research tool for historians, the media, academics, policy makers and the general public. While one would hope that the Holocaust was such an aberration that its like would never recur, the world has since learned of new and horrific genocidal undertakings. Bosnia, Cambodia, Croatia, Iraq, Rwanda, Serbia and Sudan are among the all too-many countries involved. These societies will inevitably have to confront some of the same issues which faced OSI.