Factual error: The movie takes place around the time of WWI, definitely before 1923. In the carnival scene, the calliope is heard playing "Ain't She Sweet". This was the number one song ... in 1927.
Factual error: When they are driving in the convertible, before the tarantula attacks them with the stones, if you look at their hair, it's not moving with the wind. If they were driving a convertible that fast in real life, it would.
Factual error: While the Confederate captain is explaining the mission, a couple of the "patriots" are inserting cartridges into their Colt Peacemakers. A neat trick, since the Civil War ended in 1865, and the Peacemaker wasn't introduced until 1873.
Factual error: When Roberts makes a deal with the Captain, he demands that the Captain grant liberty to both sections (i.e., the entire crew), leaving only Roberts and one enlisted man aboard as the deck watch. All U.S. Navy ships must have enough personnel aboard at all times to get the ship underway immediately, if necessary, which is why the crew is divided into watch sections.
Factual error: When Hawkins prepares to leave Princess Gwendolin's chamber, a pet cockatoo sits on a pole near the window. Now how could a parrot native to Australia - or even a "papagei" from South America, as Hawkins intones - appear in medieval England when neither continent would be discovered for several centuries?
Factual error: When Jimmy Stewart is almost down to the runway during the bad weather, the aircraft exterior shots show the type of cloud tops found only at high altitude, not low to the ground.
Factual error: The opening scene shows Spencer Tracy on a crack streamliner in the desert east of Los Angeles, featuring red and orange coaches. Such equipment was used by the railroad on only two trains, neither of which crossed the desert east of Los Angeles, and both of which had matching red and orange locomotives. In the film the train is pulled by a dark gray locomotive normally used only to haul freight, and in a close-up shot the number in the locomotive is preceded by an X, which in the language of railroading refers to an extra train.
Factual error: When Kitchener is shown inspecting Harry's old regiment, one group of African or Egyptian troops is shown to be wearing the Pattern 1914 Infantry Equipment, not made until 1914 at the earliest. Additionally, it has the 1918 modification to have two closing straps, so is over 20 years too late for the 1894 date at that point.
Factual error: The landscape shows late fall, with color and fading leaves. But on the bushes near the killer porch when Captain arrives for muffins are full of spring bloom Azaleas.
Factual error: One of the shots of individual British Lancaster bombers approaching one of the dams is actually and incorrectly an American B17, seen for only a second or two. [At no time in the film is a B17 visible in the British release of the film. However the B17 crashing appears in a version of the film released in the U.S.A.]
Factual error: Towards the end of the film, the German troops are searching for the marines and cross from the dockside to lighters and then on to a harbour launch. Although this is supposed to be in Bordeaux the launch is marked 'PLA' or Port of London Authority where the action must have been shot.