"Hegemony over Europe will be decided in battle against Russia," - Adolf Hitler
Greece Delays Operation Barbarossa
Operation Barbarossa was the name of the German invasion of Russia. Hitler had wanted to invade Russia because of their vast amounts of resources, like their ample supply of oil on May 15, 1941. But, due to his efforts in Greece, the date was pushed back to June 22, 1941. This gave the Russians additional time to gather resources and fight Germany through the winter, which Germany was not prepared for.
"The Greeks delayed by two or more vital months the German attack
against Russia; if we did not have this long delay, the outcome of the war would have been different.” -Adolph Hitler's Chief of Staff, Field Marshall Wilhelm Keitel
"The winter conditions highly favored the Soviet soldiers who were accustomed to
fighting in the weather and had weaponry suited for the conditions.
The Germans were not prepared for the harsh conditions. They didn’t have
adequate warm weather gear and had problems with the functioning of their
weapons, tanks and transportation in the harsh cold and muddy conditions" - Marissa Chmiola
Russia was able to stand against Germany in the winter and critically wound their forces in important battles like the Battle's of Stalingrad and Kursk which killed many Nazi soldiers and forced their retreat.
The Russians forced the Germans on a defensive retreat which ultimately ended in Berlin and in the victory of the Allied forces.