I've always had an interest in Urban Warfare. With the use of sewers and concrete buildings, the whole landscape can become a fortress for the defender, and hell for the attacker. However, I remember reading in the Battle of Smolensk and other similar urban combats, that direct fighting only last (for example) 10 days. Whats most interesting, is that during Operation Barbarossa, the Germans kept decent track of predicted Soviet fatalities, and they definitely kept track of Soviet Prisoners. But never, accounts of German lost or dead.
This would make sense if the German military was being beaten backwards, with lines of supply, command, and the various processes that go with it strained in the defense. However, the Germans were moving forward. I have a tendency to think that the Germans had a good account of how many they were losing, but chose not to report upon those numbers, as not to provide fuel to the Soviet cause.
Maybe their losses were more than they expected from an inferior enemy? I could definitely imagine that as a case.