Both sides failed to claim a decisive victory; the German forces occupied 90% of the city at their peak, but never managed to completely eliminate resistance, while the Soviet armies kept sending reinforcements. Both sides indiscriminately air-bombed and howitzer-shelled the city; in fact, despite the freezing temperature of -30 centigrade, air within the city was hot from the constant gunpowder explosions. Eventually, the fighting degenerated into a bloody meatgrinding house-to-house warfare, dubbed by the Germans as rat-war.
The Soviet reserves eventually broke through the outer defences, and [encircled] the city, trapping the Germans in a pocket. The German commander, von [Paulus], repeately argued before Hitler that a breakthrough retreat was vital to the German survival, but the madman Hitler prohibited retreat, which eventually caused the entire German army group to collapse.
At over a million casualties from each side, the [battle of Stalingrad] was perhaps the bloodiest battle of the war. It was especially devastating to the Germans, however, as they lost their best equipment, and unlike the Soviets, did not have [the reserve] manpower to replace the terrible losses. The battle of Stalingrad is considered the most important turning point on [the Eastern front], and quite possibly the single most important battle of the war.