The Battle of Stalingrad was the most important battle of WWII.

You're looking at the decisiveness in terms of manpower and materiel. Decisive means, according to the Oxford English Dictionary, 'Having the quality of deciding or determining (a question, contest, etc.); conclusive, determinative.'I agree, as stated before, that Stalingrad was a battle of immense importance. It just wasn't the most decisive. I shall argue henceforth for a mixture of Kursk and the Allied bombing campaign on the Third Reich from 1940-45.I am arguing for these because they operated in conjunction with each other, in terms of destroying the Axis' capacity for semi-modern warfare. At Stalingrad, the majority of the Sixth Army and the Fourth Panzer Army were equipped with the same weapons they had used in 1939, crucially, the armour and artillery. In the army approaching Stalingrad, the tanks were a motley collection including the Panzers II and III, with a few of the IV model; and even some Czechoslovak tanks from Germany's annexation in 1938-39 and captured Polish and Yugoslav tanks too, along with tanks from their Eastern European Allies of Hungary, Romania and Bulgaria. Their artillery was even more mixed, with WWI field guns, K18 Heavy Cannons and everything in between.Naturally, a sizeable portion, including nearly all of the obsolete tanks and artillery guns, were destroyed, abandoned or surrendered during the course of the battle, and Army Group South found itself in dire need of new tanks. They built hundreds of new tanks and field guns to be transported to the front line, including the Panzer V, known as the Panther; Tigers I, II and Konigstiger; the K18 heavy cannon and the new model of Nebelwerfer. Also, they had brought the Totenkopf division of the Waffen SS forward, the creme de la creme of the German army, which was all but wiped out at Kursk. Only half the number of tanks and artillery guns destroyed at Stalingrad were destroyed at Kursk, but the value of the materiel destroyed was greater, since they were fresh off the assembly line and as German tanks were upgraded, their mechanisms became more advanced and complex, meaning that they were more expensive and time-consuming to produce.Russian tanks on the other hand were incredibly simple machines, with tractor engines and parts that could be hammered out and assembled, ready to leave the factory in a few hours. They were arguably better than the Panzer IV in battle, and better than the Panzer V on campaigns. A Panther was valued at about three quarters of a million dollars in today's money, while a T-34 was valued at around half of that. Bear in mind that since the currencies they were measured in have been abolished, these are approximations.Since there was more demand for machine parts to build the tanks, more factories were built in Germany. Unfortunately for the Germans, 1943 saw the start of a huge series of allied bombing raids on German soil, and its industry was devastated. This resulted in the Axis forces, by this point nearly exclusively German, was suffering from a major shortage of armour and artillery. The German strategy was based on combined arms and rapid advance with motorised and mechanised infantry. None of this was possible with the advent of Soviet air superiority and the lack of tanks and artillery. After Kursk, the German Army was reduced to the equivilent of the Red Army in 1941 - a mass of infantry with some useless armour and artillery without competant leadership, at least in the east.