Factual error: When Lt. Dunbar is being interrogated in the Commandant's office you can see a map on the far wall. It is a map of Germany dictated by the Treaty of Versailles which ended World War I because it shows E. Prussia separated from Germany and does not include the annexation of Austria and Czechoslovakia. These annexations were completed before the start of World War II in '39 and certainly before late '44, early '45 when the film took place. It is highly unlikely any German officer would have this map displayed not only because it's inaccurate but because it displayed the territorial losses brought on by the humiliating defeat of World War I.
Trivia: Although it is difficult to tell for sure because the movie is in B&W it appears that the Commandant & guard staff are members of the Wehrmacht(regular army). Due to the extensive bombing campaign there was intense anger toward allied flyers many of whom were immediately killed upon capture; therefore POW camps containing fliers were guarded by the Luftwaffe(air force). It was felt fellow airman would be more empathic and treat the prisoners better.