Factual error: In the scene where the German East African troops are shooting at Bogart and Hepburn, their rifles are Gewehr 88 "Commission Rifles'" with five-shot magazines. In actuality, the German East African troops, under the command of Colonel Paul Von Letow-Vorbeck, were equipped with the absolute dregs of the Kaiser's arsenal: Gewehr 71 single-shot rifles, and Gewehr 71/84 8-round tube magazine rifles whose magazines usually got fouled and had to be used as single-shot rifles anyway.
Factual error: The Pretorian Guard was not as loyal to the end as shown in the movie. Actually, they were bribed into rebelling against Nero.
Factual error: There is a scene with Gene Kelly dancing at the top of the steps in Montmartre, opposite Sacre Coeur Basilica. In the background you see the lights of the Eiffel Tower. I have seen the view from the top of these steps, and the Eiffel Tower is not visible.
Factual error: Sargent Nevins (Arthur Kennedy) is shown playing a pinball machine in the military rec room. When the camera turns to the play field of the machine, it is clear that this machine has flippers, and flipper buttons are visible on the side of the body. The movie takes place in 1943, but flippers didn't appear on pinball machines until 1947. (First machine to have flippers was Gottlieb's 'Humpty Dumpty.'. (00:37:30)