What happens to the German plan? As Sixth Army advances, it has to protect its flanks, especially along the Don. So an ever-smaller part of the army is committed forward. After they clear the bend in the Don, they mount an offensive to seize the city. This is probably the most important point in the Battle of Stalingrad. They plan to seize the city by crossing the Don and advancing to the Volga in two pincers headed by panzer corps: get them into Stalingrad from the north and south, and seize it without a fight.
What stops them? As soon as they launch their attacks, the Soviets begin counterattacks. They're often suicidal and futile, but totally preoccupy the northern panzer corps and prevent it from turning any forces south toward the city. That leaves three German divisions in hedgehogs stretched along a 40-kilometer road. They never get into the factory district in the north end of the city, which becomes the site of the last battles. The southern pincer does what it is supposed to. But the Soviet reaction north of the city thwarts [Sixth Army commander Friedrich] Paulus's plan.
Where does that leave him? With one infantry corps—the only force he has to reduce the city. It has three infantry divisions in it, and a few other supporting groups—only one-third of Sixth Army. Since he can't get into Stalingrad with his armor, he goes in from the west on foot—block by block, street by street. He does try to lead attacks with armor, until each of those panzer divisions is worn out. By the time he's in the center city and trying to get into the north, German armor is gone and he's in a slug match. By October 1942, his regiments are battalions, divisions are regiments, and Sixth Army is probably a corps.
What is the Soviet strategy? To feed just enough troops into the city to keep it from falling. They are sacrificial lambs. Divisions that come in with 10,000 men have 500 the next day. Many divisions are fragments. The 13th Guards, always described as an elite force, was destroyed two months before; they're sent in half-trained and one-third equipped. The 284th Rifle Division, popularized in the film Enemy at the Gates—only one of its three regiments has rifles. It's like Muhammad Ali's rope-a-dope. It was so brutal that Stavka, the Soviet high command, forbade A. I. Eremenko, Stalingrad front commander, and his commissar, Nikita Khrushchev, from crossing the river into the city: Stavka was afraid they'd develop an affinity with the poor troops dying there and decide to abandon it.
How do the Germans react? For them it becomes a meat grinder. Every division they send in is weakened, so they have to pull new ones off the flanks. According to Sixth Army's loss figures, most divisions go in rated combat-ready. Within a week, they're rated either as weak or exhausted. The attrition rate is phenomenal. The Luftwaffe's rubbling of the city only exacerbates things. In early November, they run out of divisions. It's a true war of attrition.
How do they maintain the offensive? They take all the engineer battalions out of Army Group B, which makes the final attack on November 11. So they have nobody to defend the Don, except Italians and Romanians. Hungarians are already in the line. Army Group B's left flank is an allied army group. The Soviets understand that weakness from their intelligence, and that's where they launch their counteroffensive.
What kind of leader was Stalin? The myth is that Stalin micromanaged the first year, then at about the time of Stalingrad began deferring to his commanders, and thereafter the commanders fought the war under his general guidance. That's wrong. He was hands-on throughout. In 1941, his stubbornness and insistence on fighting back cost him a lot, but also ensured that Hitler's key assumption--that the Red Army would dissolve once it was smashed--didn't happen. By 1942, after Leningrad and Moscow, Stalin and Marshal Georgi Zhukov think alike. They understand that even if you have to ruthlessly expend manpower, resistance will wear down a numerically weaker opponent. That tactic cost probably 14 million military dead--the price of defeating a more experienced, battle-worthy, savvy Wehrmacht.