See the article at: http://www.washingtonpost.com/blogs/worldviews/wp/2015/05/20/the-fascinating-story-of-the-alcoholic-womanizing-german-double-agent-who-turned-the-tide-of-world-war-ii/?tid=pm_world_pop_b
Why did not Stalin warn about the Pearl harbor attack if he believed the nazis would attack? Two-faced as usual? Let them have it....??
Stalin was never, ever a friend of the United States. He just had an enemy in common with them for a while.