Reasons why the Soviet Union signed a Nonaggression pact with Germany

Hitlers intention all along was to invade Poland. The only way he could do that without interference from Russia was to sign the Pact and allow Stalin to invade Finland without interference. That pact put all the pressure on France to declare war on Germany and split their forces(which weakened them tremendously) to stop the Germans and to monitor the Russians. The "Pact" back fired on Stalin as the Fins kicked the Russians butts. Hitler licked his chops because France was left all alone to defend a very long border. By the time the British tried to come to the aide of the French it was far too late as the "Blitzkrieg" had already proved how outdated the French military strategies and defenses were.

Advantages the Soviet Army had over the German Army

They took advantage of Germany's flanks, which were poorly guarded by Romania and Italy. Once the flanks were out of the way, they blocked supply routes and essentially surrounded the 6th Army within Stalingrad. In the end, though, 2 things helped the Russians win the battle - the bitter cold of a Russian Winter (that Hitler had failed to take into account though it had been the same thing that stopped Napoleon from capturing Russia more than a century earlier) and their resilience. Even when the German's controlled 90% of the city in the early stages of the battle, the Red Army refused to surrender and resorted to house-to-house combat.