As the old saying goes, the enemy of my enemy is my friend. There are exceptions though — like when the enemy of your enemy is a Nazi.
However, that didn't stop the U.S. government from recruiting up to 1,000 ex-Nazis during the Cold War to spy on the Soviet Union and counter the red menace, according to The New York Times, citing thousands of new documents released under Freedom of Information Act requests and other sources. The main offenders appear to be the FBI and the CIA, which in the 1950s recruited ex-Nazis despite their "moral lapses," as one American official put it, in perpetuating Hitler's empire.
One recruit, for example, was allegedly involved in the wartime killings of some 60,000 Jews in Lithuania. Still, the U.S. employed him as a spy starting in 1952, before allowing him to emigrate to the U.S. four years later, where he lived peacefully until he was outed in the 1990s and prosecuted. The CIA at the time tried to prevent his prosecution, but failed.