Factual error: During all the major battle scenes involving tanks the Germans are using post-WWII tanks. The turret looks a bit like the M10 Wolverine with a top cover.
Factual error: At the very start of the film, as the Sergeant stabs a German soldier in the Great War, you get a good view of his "modern" rubber soled boots.
Factual error: As the platoon fights their way through the Normandy hedgerows, the sergeant tells the men that he fought in the area during WWI. However, that area was far behind the trench lines located North of Paris, not too many Boche in Normandy in 1918.
Factual error: Mark Hamill shoots a German several times in the incinerator, a total of 18 rounds without reloading. The M1 holds an 8 round clip. There was no pause at anytime for him to reload.