On June 22, 1941, Hitler ordered the Wehrmacht to invade Soviet Russia, and by doing so he changed the course of history of not only Germany, Russia and WW2 but of the whole world.
Hitler felt that all he needed to do was “kick in the front door" of the Soviet Union and watch the whole rotten structure come crumbling down. He thought he could bring down the entire Soviet Union in as little as a month or two. Hitler didn’t feel like his mighty Wehrmacht needed winter gear, what with all them being unstoppable Aryan supermen and all that.
Six months after the German invasion, the German army was at the outskirts of Moscow, and some forward positions even reported seeing the towers of the Kremlin from their field glasses.
If Moscow fell, Russia would follow, and if Russia fell, the war in Europe would have been won.
But then, the advance stopped.
The Russian's greatest war ally had arrived on the battleground, no, not "Lend-Lease", but “General winter”.
Late 1941. This German light armored car is just 100 Kms from Moscow.
The harsh siberian Russian winter and the fact that Stalin was willing to sacrifice any amount of people in order to stop the German advance helped turn the tide of war in Stalin's and the USSR's favor.
Around 8 to 11 million were red army soldiers died in the eastern front, almost half of them were not Russian but were Ukrainians,Georgians, Belarusians and many other nationalities from all over the USSR.
In total some 26 million Soviet citizens died during the war. While most of them died because of the Wehrmacht's war crimes, genocidal tactics and just plain barbarity, millons also died because of Stalin's "scorched earth" tactics which led to widespread famines.
However, even this unimaginable sacrifice of human lives would probably not have been enough to stop the Wehrmacht if it hadn't been for the Russian winter, and the German army complete and utter lack of preparation for it.
But one would expect that Hitler would have prepared for such an eventuality, like a harsh Russian arctic winter, I mean we're talking about Russia here, RUSSIA, which is basically a byword for “A very, VERY, cold place”.
Well in reality the Germans were inexcusably unprepared for the harsh cold of the Russian north, thanks to their Fuhrer who thought that the whole of the USSR, one of history's largest contiguous land based empire, would fall in two to three months and so he never even bothered to be prepared for a long and drawn out conflict.
Once the Russian winter set in, tanks froze in their tracks, men froze in their sleep, supply lines bogged down, and the whole German invasion came screeching to a four-month halt.
German soldiers taken prisoners near Moscow. Early 1942. Notice their lack of winter clothings.
By the time the Russian winter passed and the spring 1942 arrived and the Germans renewed their offensive, it was too late.
The Soviets had recovered just enough during the winter to stabilise the front and hold them at bay. In 1943, following their long and drawn out victory in Stalingrad, the Soviet Army won the biggest battle in WW2, the battle of Kursk, and turned the the tides of war.
The USSR had to face and defeat around 214 German divisons on the Eastern front, comprised of the the very best the German army had offer in terms of men and equipment.
While the Red Army suffered enormous losses during the war, it was also responsible for around 80% of all German Combat casualties in WW2.
The failure of the invasion of Soviet Russia, ended up costing Germany and its Fuhrer not just the war, but their "1,000 year reich" and even Germany itself.
Throughout the war in the eastern front, Hitler continuously ignored the advice of his top generals and instead thought that he - a corporal who served in WW1 as a regimental runner who spent nearly half his time at the regimental headquarters well behind the front lines - knew better than all of the battle hardened and experienced German generals put together.
Tens of thousnads of German prisoners of war, captured during Operation Bagration, were made to walk along the streets of Moscow in 1944
In conclusion, if Hitler wasn't a complete amateur and had properly equipped his soldiers and armies with proper winter gear, and that meant not just clothing for troops but also proper all-terrain and all-condition equipment and gear for vehicles/machinery/tanks/artillery/aircraft/ like any sane commander would have done in his place, then the Wehrmacht would probably have been able to press its attack, seize Moscow, conquer Russia and win the war in Europe.
Instead it was the Red Army and Stalin who ended up as the biggest victors of WW2, in no small part thanks to Hitler and his military blunders and mistakes.
Norman Davies, "No simple victory."
Antony Beevor, "Stalingrad".
Timothy D. Snyder, "Bloodlands."