The German invasion of the Soviet Union was stopped with:

Several factors contributed to the Soviet Union being able to stop the German invasion, called Operation Barbarossa.

First, Hitler and the German High Command underestimated the strength of the Soviet troops and the number of reserves the Soviets could call up. They also underestimated the number of tanks, airplanes, and other war machinery that the Soviets had, although much of the machinery was old or in poor repair. Hitler and his advisors also wasted time by arguing about the course they should follow. They also thought that the Soviet Regime would collapse from lack of domestic support.

The Soviet policy of scorched earth also affected the German invasion. As the Germans advanced, the Soviets burned crops, destroyed bridges, dismantled and moved steel and munition plants, evacuated factories, and destroyed or moved railroad cars (Germaine railroad cars used a different gauge of track that that of the Soviets, so they could not use German rail cars on Soviet tracks). As the Germans advanced into Russia, it became more difficult to keep the troops supplied.

Weather was another important factor. Rains in July turned the sandy Russian roads into mud, slowing the transport vehicles which traveled behind the German tanks. In October, during the Battle of Moscow, the weather turned to rain and then to snow and sub zero temperatures. The German troops were ill-prepared to fight in the cold weather, with no provisions of winter clothing, and the cold affecting the Germans’ mechanized transport, tanks, artillery, and aircraft. The Soviets were well provided for in the cold weather and fought more effectively in the cold weather than the Germans. Added to the cold weather was the fact that the German troops were tired and the number of troops began to decline with no new troops sent to replace them.