Prior to the start of WW II Germany built some fairly impressive fortifications on their eastern frontier. Since these were still in existance and, likely mostly intact in late 1944 what effect did these have on the Soviet final push to Berlin? None of the major common texts on this period of the war make any real mention of these fortifications and none state what effect they had on the battle outcome.
It would be interesting to know more about how these fortifications effected the battle.