Yes “The Battle of the Bulge” was probably the least authentic war movie ever made. They filmed it in the desert.
I watched that movie with my Grandfather. He saw it (his words) “on its first run, in Technicolor”.
Afterwards, I asked him what he thought. He said that “it was a fine movie, but no one looked cold enough”.
Changed the way I watch war movies forever. Now I judge them on how cold or hot, dirty, hungry, exhausted, tired and generally miserable the actors look.