Factual error: Rifles and more so, cannons of the type shown in the movie were not close to being invented in the 1500s.
Factual error: When an older lady working for the German cause is collecting items from the US Soldier's room (Garner), she picks out a letter with stamps on it that were not issued until 1954 and 1961...even though the year of the movie and scene is only 1944.
Factual error: When the prisoners are taking a shower Roberts says to another prisoner as he goes to turn on the water "not that one, it turns on the gas" - a reference to Nazi death camps that used shower rooms to gas people. But this film is set during WW ll when this info was not known by rank and file soldiers - it only became known near or even after the end of the war.