How did the Soviet Union help defeat Germany in World War 2?

On June 22nd 1941 Nazi Germany invaded the Soviet Union at 0400 GMT. At 0500GMT the propaganda minister of Germany Joseph Goebbels announced a statement from Hitler declaring that the mobilization of the German army would be the "greatest the world has ever seen".

In 1939 Germany and The USSR had signed a non-aggression pact which was obviously broken when the German army of around three million crossed the border and started to attack. It was code named "Operation Barbarossa".

The USSR had a very large force of around nine million men in arms and about half a million in reserve however they were at a great disadvantage when it came to skill and battle tactics