In mid 1942, with a growing house-to-house battle in the Soviet city of Stalingrad, General Secretary Stalin orders the next major Red Army offensive against the German occupiers in Leningrad, the Sinyavin Offensive, cancelled. The bulk of its forces will relieve defenders around Moscow and the Ukraine front so that those troops could be diverted to the front at Stalingrad.
this allows Hitler to follow through with his planned offensive to finally take the besieged northern city of Leningrad, Operation Nordlicht (Northern light)
On August 23, the Wehrmacht opened the offensive with a massive artillery and aerial bombardment of the city, one of the largest seen in the war thus far.
A week later, the defenses of the city in ruin, the panzers of the German 18th Army begin a steamroller-drive into the outskirts of the city. No halt orders are given, despite the dense suburban environment and stiff Soviet resistance. despite being without proper provisions for months, the week-long bombardments and poor weapons, the Soviets do delay the panzer's approach, inflicting up to 50% casualties on some panzer brigades. but, reserves committed, the Germans break the defenders and pour into the heart of the city. Before any German commander realizes it, Leningrad has become another Stalingrad. Advances are slowed, almost halted, as the Soviets put up house-to-house fights, mining every street and booby-trapping every building.
The Red Army reinforcements given to the Wehrmacht in Stalingrad succeed not only in halting the Germans, but by the time of the similar battle unfolding in Leningrad, pushed the German 6th Army out of the city, inflicting crushing numbers of dead and wounded. despite being told by the Führer himself not to retreat, Von Paulus, the commander of the 6th Army, withdraws and orders his men to dig in and bombard the city.
By October 1, Leningrad was mostly in German hands. Only few blocks were still garrisoned with Red Army troops and partisans, and these were quickly surrounded and destroyed. Estimated casualties of the German offensive were some 100,000 soldiers, to 300,000 Soviet soldiers and civilians.
In Stalingrad, the Red Army launches an offensive into the 6th Army, suffering heavy losses but succeeding in regaining a great deal of ground around the city, and threatening the left flank of German Army Group south's entire operation in the Russian Caucasus, grounding their advance to a halt.
By the tenth of October, the swastika flies over almost every pile of rubble in what once had been the Leningrad, second city of the Soviet empire, and what was now a German trophy.
However, Operation Nordlicht was planned to have freed up to 450,000 German soldiers for offensives north to take Murmansk and cut off Allied aid through that port. It was now too late in the year to mount such an offensive as the first snows are already falling. Casualties were also much higher than expected, and occupying the city would absorb even more German troops.