To protect itself, the Soviet Union joined hands with Britain. And became a part of the Allied Powers. They formed a plan together to send supplies to the Soviet Union army. They decided on a route through Iran. But the problem was that the Iranian Government favoured Hitler. This is why the UK and the Soviet Union invaded Iran together.
This wasn’t very beneficial, because Hitler’s Blitzkrieg strategy helped the Germans invade 100 km within 2 days and occupy a large amount of Soviet Union territory. Within some weeks, they had proceeded so much that they were only 300 km away from Moscow. By this point in time, Hitler and his military commanders had some disagreements. Due to this, the next German advance, was delayed till October. It started getting colder.
The cold season gave the advantage to the Soviets. They were accustomed to fighting in the cold. On the other side with Japan, the Soviet Union found their second advantage there. Japan and the Soviets had signed a Non-Aggression Treaty. This meant that the Soviet Army troops stationed at the Eastern border fighting with Japan, they could return to the West and fight Germany to defend their country.
