Factual error: In the aerial shot over rural Britain near the beginning of the movie, there are two modern cars visible. Too new to be early 40's models.
Factual error: When we are in the Colonel's office at the US army base there is a US flag in the corner. It has 50 stars on it, as you can tell by the pattern. There were only 48 stars on the flag during WWII.
Factual error: When Michael Caine is standing outside the village church, it is clearly visible that double yellow line road markings have been blacked out (covered up). The film is set during the war, but double yellow lines did not make an appearance in the UK until 1958, therefore it is clear that the filmakers blacked them out to avoid an anachronism.
Factual error: When Steiner meets Colonel Radl and Liam Devlin on Alderney they are watched by two civilian fishermen. The events of this film take place in 1943, but all civilians were evacuated from Alderney to the mainland in 1940.
Factual error: When Steiner is discussing with the SS General about "difficult decisions are the privilege of rank..." he addresses him as Herr Gruppenführer (Lt. General) he should have addressed him as Herr Obergruppenführer (Full General).
Factual error: Near the end of the movie, (when Larry Hagman enters the traitor lady's house), a grenade ends up exploding at the bottom of a flight of stairs. After it goes off, an American soldier runs up the stairs, firing at the lady in an upper room with an M1 carbine: RIPPING ON FULL AUTOMATIC! (The M1 carbine was semi-automatic until the selective-fire M2 variant was produced after the war).
Factual error: When Col Steiner is imitating the American's voice over the radio he uses the words "Delta-1" or similar. Delta is part of the NATO phonetic alphabet which wasn't introduced until 1956, well after the war had ended. "Dog" would have been the correct word to use.
Factual error: The M1 carbines that the Americans uses are fitted with a bayonet lug enabling a bayonet to be fitted to it. This feature wasn't available till AFTER WW2 and first saw service in Korea.
