In both the movie and novel, it is stated that Colonel Radl fought in the "Winter War". The "Winter War" is today normally used to describe the Soviet invasion of Finland of 1939-40, of which Germany had no official part in.
In the novel, the same name "Winter War" is used to describe the German invasion of Russia, more specifically the winter campaign of 1941, early 1942. This MAY be the correct contemporary description of the German invasion-winter campaign, or it could be an overlook by the author of the novel which was in turn translated to the movie.