After the fake skirmish goes wrong, resulting in Mother's death, the GIs go back to the chateau where they are debriefed by Griffin. They then spend the night at the chateau and are all chased away the next morning (taking Mother's body with them) by the advancing German Army. They spend that night in the woods hiding from the Germans, and the next day, decide to bury all their equipment and make their way as best as they can back to Allied lines with Mother's body in tow. But, as they re-position Mother's body on the litter, they are able to easily bend and unbend his arms even though the body has been exposed to subfreezing temperatures for about 48 hours. Surely, anywhere outside of a Hollywood movie locale, Mother's body would have experienced rigor mortis and frozen solid by then, making his arms rigid and hardly bendable.
Throughout the movie, the forest is predominantly comprised of white birch trees. This species is native only to North America and does not grow in the Ardennes Forest where the events take place.