: Popov was a critical piece of the D-Day deception, helping convince German high command that the Allied invasion would land at Calais rather than Normandy.

Popov spent the war feeding the Germans carefully vetted "intelligence" that made him one of their most trusted assets while secretly advancing Allied goals.

: In 1941, the Abwehr sent Popov to the U.S. to scout defenses, including Pearl Harbor. He attempted to warn the FBI of the impending Japanese interest, but J. Edgar Hoover ignored the warning, dismissing Popov as a "moral degenerate".