Factual error: A convoy of open trucks arrive at the camp bringing the latest batch of prisoners, many of whom are carrying rucksacks and tote bags of clothing and other possessions. Where did they come from? Combat servicemen in World War Two did not carry overnight bags with them - a change of clothes or a handy supply of toiletries was the least of their concerns. A prisoner of war arrived in the camp with the clothes he stood up in and nothing else.
Factual error: Many of the prisoners are wearing watches, which is incorrect. Upon arrest a prisoner's watch was confiscated. This prevented them using them to bribe or barter with corrupt guards (and as this film acknowledges, there were plenty of those) as well as making coordination of meetings or escape plans difficult.
Character mistake: The scene in the outdoor Parisian cafe is incredibly daft. First, the cafe owners call James Coburn's bizarrely-accented Australian to the telephone to keep him out of the way as their accomplices assassinate three uniformed German officers seated in the cafe in a drive by shooting. They then toast the killings with cognac, and that is the mistake - not the shootings, not the luring away of Coburn - the mistake is that the cafe proprietors celebrate the assassination of the German officers in broad daylight, in the open, without even stopping to think that such an action would have them shot, because all of this is done in the direct view of passers-by in broad daylight. Do they think those three German officers were the only ones in Paris? How did they know Coburn wasn't an undercover Gestapo agent or a French collaborator? Don't they stop to consider that in an occupied city machine gun fire is going to draw some attention from the authorities, who might just wonder what a couple of bullet riddled corpses are doing lying about the place?
Character mistake: When Werner asks Hendley why, as an American, he fights alongside Britain, he mentions that the British burned down the U.S. capital in 1812. While it happened during the War of 1812, the burning of Washington actually occurred in 1814. (00:11:10)
Factual error: When the SS and Gestapo are leaving Bartlett in Von Luger's office on his arrival in the camp, they all give the Nazi salute with bent arms. The correct form was a straight outstretched arm and hand: only Hitler himself was allowed to give the Hitler salute so sloppily.