During the siege of Leningrad (8 September 1941–27 January 1944) the Germans engaged in a systematic bombardment of civilian and military infrastructure in an attempt to crush the morale of those trapped inside. By the end of 1941 the incendiary bombs and shells fired into the city had destroyed the wooden warehouses in the southern districts along with all the stockpiled food reserves. Under forced labour many civilians were made to build defensive fortifications within the city as a last line of defence should the Germans break through. Transport infrastructure and power was made unavailable for civilian use meaning that many thousands froze and starved to death in the bitter winter temperatures. Small amounts of supplies could be brought into the city by trucks which risked driving over frozen Lake Ladoga to the east, and by February 1943 Operation Spark had regained control of the Leningrad–Moscow railway, allowing more supplies to be brought in.