Anachronisms: When Henry's wife and friend are trying to save him, several people have gathered to watch the action. A young woman in this small crowd has a 1960s "flip" hairdo, yet it had been established earlier that the story takes place during World War II.
Revealing mistakes: As the German U-boats are intercepting the US convoy, the lead U-boat's propellers are not spinning.
Anachronisms: When Henry is dreaming about his military parade a flying wing is shown and is jet propelled. There were no jet propelled flying wings during WWII for the Americans.
Revealing mistakes: Right at the start, the admiral and lieutenant are striding purposefully through the corridors of the Pentagon. The second set of doors they pass through is marked "Restricted Area" & "Secret". The doors are opened by two marines to reveal a long lighted corridor; this is shown to be a painting as the officers walk through the doorway but then go left instead of straight on; as the doors close behind them, the whole corridor dims briefly as they walk in front of a light.