Erich von Stroheim had a very large input on the depiction of his character. He designed his clothes and the neck brace that he wore in the film. He even wanted black sheets on his bed but Jean Renoir drew the line at that request.
When Lt. Maréchal is climbing down the rope from the watchtower the wooden window shutters can be seen closing above him even though he closed them himself minutes prior.
As the WWI German soldiers are celebrating a French fort's capture, the map on the wall of the officers club is clearly an inter-war (1919-1938) map of Germany.