Though the German forces in East Prussia had no realistic hope of victory, and were severely short of manpower, ammunition, and fuel, they continued to offer strong resistance, inflicting extremely high casualties (584,788+) on the Red Army during the East Prussian Operation. "Ad hoc" battle groups were often bolstered by civilians press-ganged into the "Volkssturm", and many East Prussian villages and towns had been turned into fortified strongpoints, in addition to the substantial fortifications centred on Heilsberg. The fighting was prolonged in order to keep open civilian escape routes, and because requests to evacuate the main body of the Fourth Army were refused by the German High Command.