Factual error: There is no way that Col.McNamara could allocate which hut men went into. The Germans controlled this. Also there is no way he could just turn up at the Camp Kommandant's office unannounced and talk to him.
Factual error: The date at the start of the film is 16th December 1944, which was the first day of the German Ardennes offensive. The opening scenes show snow on the ground and roads. When the offensive started the weather was wet and foggy. It didn't snow until Dec 24th.