His first post-war job was going through files trying to find Nazis for his nominal employer, the US Navy, so they didn't get admitted to the US.
His informal employer Allen Dulles wanted access to those files too and got it. He had a different goal: to pave the way into the US for his Nazi friends.
Nixon was rewarded for his treachery against the United States by being backed for Congress by George Herbert Walker Bush's father, a banker and money launderer for Nazi industrialists before, during and after the war. Jack Ruby was sent from Chicago to help work on the campaign.
Sounds crazy, doesn't it? Just look it up.
And while you're doing that consider that this is the piece of human garbage the American people elevated to president twice.