Snow did play a major role in the defeat of the German's in the Battle of Moscow - along with many other things. The German Army was not prepared for snow simply because they didn't think they would be fighting in Russia for that long.

"Neither Hitler nor the General Staff anticipated a long campaign [Barbarossa] lasting into the winter, and therefore adequate preparations, such as the distribution of warm clothing and winterization of vehicles and lubricants, were not made."

Hitler said himself "We only have to kick in the door and the whole rotten structure will come crashing down." That belief was drilled into everyone's heads, even the front line troops. They believed that the Russians were not a formidable enemy. After Stalin's Military purges the command structure was weak. The Russians failure to achieve victories in the Winter War was further evidence of this. Victory for the Germans would be swift, and hence no preparations were made for winter fighting.

In the opening Phases of Barbarossa (started on 22 June 1941), German victories were relatively swift. However, Russian forces were fighting much more ferociously than expected. Several Soviet pockets of defense (Minsk-Białystok) had to be eliminated before infantry divisions, which were mostly horse-drawn could catch up to the advancing Panzer armies. By August 1941 the Germans finally captured Smolensk, an important stronghold on the road to Moscow.

"At this stage, although Moscow was vulnerable, an offensive against the city would have exposed the German flanks. In part to address these risks, in part to attempt to secure Ukraine's food and mineral resources, Hitler ordered the attack to turn north and south and eliminate Soviet forces at Leningrad and Kiev. This delayed the German advance on Moscow. When that advance resumed on 2 October 1941, German forces had been weakened, while the Soviets had raised new forces for the defense of the city."

On October 2nd when the attack on Moscow resumed the Germans had finally realized they had underestimated the Russians ability to produce satisfactory reserve troops. Their first attack objective was to eliminate three Soviet fronts forming a defensive line between the cities of Vyazma and Bryansk, which barred the way to Moscow. Using blitzkrieg and pincer tactics, their attack trapped 4 Soviet armies in a pocket between Vyazma and Bryansk, while the rest of Soviet armies pulled back to set up a better defensive line around Mozhaisk.

It was around this time on October 7th that the first snows came. However, they quickly melted and turned the roads into muddy impassable quagmires. This was known to the Russians as the rasputitsa.

With the rasputitsa weather present the German advances began to slow drastically. All the while Russian counter-attacks from the pocket also wore down German fighting strength. When the Germans pressed on to tackle the Mozhaisk defense line on October 13th they found moment quite difficult,and to make the matters worse the German supply lines where severely disrupted by both long distances and the Winter weather. On October 31st all German offensive operations were halted until the weather conditions improved.

However, they never did improve and actually got much much worse. "The German forces were worn out, with only a third of their motor vehicles still functioning, infantry divisions at third- to half-strength, and serious logistics issues preventing the delivery of warm clothing and other winter equipment to the front." In November and December the temperature dropped to as low as –49 °F.

"These numbers indicated severely cold conditions, and German troops were freezing with no winter clothing, using equipment that was not designed for such low temperatures. More than 130,000 cases of frostbite were reported among German soldiers. Frozen grease had to be removed from every loaded shell and vehicles had to be heated for hours before use. The same cold weather, typical for the season, hit the Soviet troops, but they were better prepared."

While the Germans hunkered down for the winter weather, the Soviets which were much more use to and prepared for began a counter attack in an attempt to push the Germans away from Moscow. Which they succeeded in doing, and eventually pushed the Germans 100–250 km (62–155 mi) from Moscow. Nearly surrounding 3 German Armies in the process. The Soviet counter attack eventually ran out of steam on January 5th.

So all in all, the Germans underestimated the Soviets fighting forces and their ability to replace lost troops. They Soviets also had better winterized equipment and outnumbered the Germans. Although the Germans had made great progress, the lack of paved roads and horrid weather hindered their advance, because supplies could not be brought up from such long distances in time. Also Soviet resistance was much stronger than expected, and Hitler being the armchair General he was did not listen to the advice of his Generals and delayed the capture of the city. Thus the attack started late and Winter weather worked against his unprepared armies.