They were the only Soviet winter surface routes into the city while it was besieged by the German Army Group North under Feldmarschall Wilhelm Ritter von Leeb.
In January 1943 the Soviet's Operation Iskra broke the encirclement, and the ice roads were used in conjunction with land routes for the remainder of the winter.
[1][2] The routes carried supplies necessary to sustain life and resistance inside the Leningrad pocket, and evacuated non-combatants, wounded, and industrial equipment.
[5][6] The Soviets fell back onto transport by ship over Lake Ladoga and by air;[4] the evacuation of strategic industries and personnel, and shipments of munitions from Leningrad, continued.
[9] The Soviet Leningrad Front under General Ivan Fedyuninsky launched its own offensive toward Sinyavino on 20 October to recapture Shlisselburg corridor and break the encirclement.
[11] The railroad cut was temporary; the exhausted Germans could not hold the salient in worsening weather and against increasing Soviet pressure.
The poor feeder forest roads from Zaborye - the closest railhead before the recapture of Tikhvin - exacted their own toll in abandoned and unserviceable vehicles.
[18] On the day of the first truck convoy, Leningrad officials asked the State Defense Committee (GKO) to support the road.
[19][20] The Leningrad Front planned the ice roads to bring 1965 tonnes of supplies to the city per day, but this was not initially met.
[22] The supply organization was poor[21] leading Andrey Khrulyov, head of the Rear of the Red Army, to order Andrei Zhdanov, the Leningrad Communist Party secretary, to make the ice road more efficient on 7 December;[20] performance slowly improved after Zhdanov and Alexey Kuznetsov took charge of the supply effort.
[18] By the end of December the ice was 1 metre thick and covered by 30 centimeters of snow, able to support unlimited use and heavy vehicles.
Leningrad was left to evacuate civilians as best it could; only 36,118 evacuees, plus an unknown number who bribed truck drivers or illegally made the trip on foot, crossed the lake out of the pocket between 6 December and 22 January.
Industrial equipment from 86 plants and factories and some art and museum collections[27] were evacuated starting in December 1941, and 20% of the 3677 railroad cars were transferred over the ice roads.
[29] On 2 April 1942, a meeting at the Kremlin with the Anastas Mikoyan approved construction plans for an underwater fuel pipeline through Lake Ladoga to Leningrad.
[30] The State Defense Committee ordered the Red Army to construct the pipeline on 25 April, and it entered service on 18 June.
Retaking the Shlisselburg corridor prevented the Germans artillery from bombarding the ice road, although ineffective air attacks continued.
[14] Due to its size and unpredictable weather conditions, many speculated that the construction of an ice road connecting its shores would be impossible.
Even during winter, the region's erratic winds were capable of increasing or decreasing the lake's water level by as much as four feet (1.2 m) within just a few hours.
[17] Construction was carried out in the face of inclement weather, changing and hazardous ice conditions, and German artillery and aerial bombardment which required camouflage and anti-aircraft defences.
[22] Once the route had been confirmed and tested for stability, larger plows and snow carving machines were then used to widen the ice road and make it more suitable for automobile transport.
[22] By February 1942, large snow banks on either side of the route had been made into massive ice walls, which shielded transport from the lake's harsh winds.
Later, settling weather and high snow walls flanking the roads made control easier, allowing the interval between posts to increase to 1-2 km.