Like emphasized earlier, November 1942 was a very crucial time in WWII.
On November 19th 1942, the Red Army started Operation Uranus, on both flanks of the German 6th Army, besieging Stalingrad. During September and October, 6th Army had done hard fighting to control the city , with house to house street fighting and incurring heavy losses on both sides.
At the time, Red Army front in Stalingrad was reduced to two separate bridgeheads, fighting with the Wolga in their back. But due to the concentration of troops in Stalingrad, the adjacent German front, over a large stretch was rather weak. The goal of the offensive had been to install a defence line along the River Don, protecting the real target of Case Blue, seizing oilfields across the Caucasus, an operation that had meanwhile nearly stalled. Concentrating on Stalingrad had been no part of the original plan.
Apart from the length of the frontline, there were two other weaknesses. During their fast drive east in summer, the 6th Army had often ignored to eliminate pockets of Soviet troops on their side of the Don, leaving the latter useful bridgeheads for a counteroffensive. Secondly, the flanks of the 6th Army were defended by Romanian and Italian troops, which were much less trained, armed and motivated than the Germans. German high command had warned Hitler about this dangerous situation, but he had ignored it, being convinced as he was that the Red Army was finished.
With Operation Uranus, the Red Army easily broke through these weak flanks and encircled the 6th Army. It completely surprised the latter’s commander, General Paulus, who, ironically, found himself and his staff outside of the cauldron. Paulus suggested an immediate breakout, but Hitler ordered him to stay at the Wolga. The encircled army would be supplied by airlift, and a relief force would be sent.
But being encircled meant that 6th Army had to make front on all its sides and hence retreat deeper into the cauldron, lengthening the distance, the relief force would have to make its way. It took three weeks to assemble the relief force, commanded by General Manstein, giving of course the Red Army time to reenforce the encirclement.
Manstein’s offensive started with a difficult choice! Taking the shortest route seemed logic, but that meant he would have to cross the River Don. To avoid that, he had to start from no less than 100 km further away from Stalingrad. He choose the latter option. Initially, he advanced swiftly. The encircled troops heard (and saw at night) the rumble of the relief force nearing. But at the end of December, it became clear for Manstein, that he was running out of means, against a stronger force, and he would not make it. He had meanwhile approached the cauldron only 45 kilometers. So, Manstein suggested Paulus to ignore Hitler’s orders, and try to break out from the encirclement, to make contact with the relief force.
Now Paulus had a dilemma, he considered, and concluded that a), he had only resources and fuel for some 15 kilometers, so he feared to end up in the open plains, amidst the harsh Russian winter; b) while inside Stalingrad, the ruins offered at least some protection against the weather; c) he would have to abandon positions that had cost a high sacrifice to capture them, and d) he would have to abandon the wounded. So Paulus said it could not be done. Manstein then turned to Hitler, who did not veto the proposal, but consulted Paulus, who repeated he did not have the resources for a 45 km breakout. So, Hitler informed Manstein that 6th Army was not capable to put up a breakout. Manstein was soon forced to retire.
Meanwhile, the promised airlift never managed to supply the needs of the encircled army. Nevertheless, the 6th Army, despite starvation, cold and disease, kept on fighting, a resistance that allowed the troops from the also failed Caucasus campaign, to retire safely during January. On January 31st 1943, 6th Army surrendered.