A secret history of the United States government's Nazi-hunting operation concludes that American intelligence officials created a safe haven" in the United States for Nazis and their collaborators after World War II. The 600-page report, which the Justice Department has tried to keep secret for four years, provides new evidence about more than two dozen of the most notorious Nazi cases of the last three decades. Perhaps the report's most damning disclosures come in assessing the Central Intelligence Agency's involvement with Nazi migrs. Scholars and previous government reports had acknowledged the C.I.A.'s use of Nazis for postwar intelligence purposes. But this report goes further in documenting the level of American complicity and deception in such operations. The Justice Department report, describing what it calls "the government's collaboration with persecutors," says that O.S.I. investigators learned that some of the Nazis "were indeed knowingly granted entry" to the United States, even though government officials were aware of their pasts. "America, which prided itself on being a safe haven for the persecuted, became - in some small measure - a safe haven for persecutors as well," it said. The Justice Department has resisted making the report public since 2006. Under the threat of a lawsuit, it turned over a heavily redacted version last month.