Revealed: How the CIA protected Nazi murderers

US shielded war-time collaborators to try to destabilise Soviet Union

Declassified CIA files have revealed that US intelligence officials went to great lengths to protect a Ukrainian fascist leader and suspected Nazi collaborator from prosecution after the Second World War and used him to stir up trouble inside the Soviet Union from an office in New York.

Mykola Lebed led an underground movement to undermine the Kremlin and wage guerrilla operations for the CIA during the Cold War, said a report prepared by two scholars under the supervision of the US National Archives. During the Second World War, Lebed helped to lead a Ukrainian nationalist organization that collaborated with the Nazis in the murder of the Jews of the western Ukraine and also killed thousands of Poles. The report details post-war efforts by US intelligence officials to throw the federal government's Nazi hunters off his trail and to ignore or obscure his past.

The report, titled Hitler's Shadow: Nazi War Criminals, US Intelligence, and the Cold War, draws from an unprecedented trove of records that the CIA was persuaded to declassify, and from more than a million digitised army intelligence files that had long been inaccessible. Among other things, the authors say, the files also show that US intelligence officials used and protected ex-Nazis during the Cold War to a greater extent than previously known.

Elizabeth Holtzman, a former Democratic congresswoman from New York who fought for the disclosure of Nazi files, welcomed the release. "This is a difficult, and in some respects shameful, chapter in American history," she said. "It was not known to the public, and I think it's a mark of governmental courage and of national courage to take this era and these documents and say, 'We want to learn the truth about what our government did', and to do it in a way that was professional and serious."

In 1949 the US government brought Lebed to New York, where he was safe from assassination. Through his CIA-funded organisation, Prolog, he gathered intelligence on the Soviets into at least the late 1960s. In 1991, he was still considered a valuable asset to the agency, the report said. Lebed was eventually identified by federal investigators as a possible war criminal but was never prosecuted. He died in 1998.

One of the report's chapters deals with how the Americans used Gestapo officers, including Rudolf Mildner, after the war. Mildner oversaw security in Denmark in 1943 when most of the country's 8,000 Jews were ordered to be arrested and deported to Auschwitz – though they were rescued after Danish resistance leaders were tipped off. The US army detained Mildner and saved him from war crimes investigators because his knowledge of Communist subversion was considered useful.

Nazi hunters and lawmakers have long raised questions about the US government's involvement with war criminals during the Cold War. Between 1945 and 1955 alone, more than 500 scientists and other specialists with Nazi ties were brought to the US, and went on to play major roles in such fields as missile development and the space programme.