Wikipedia article on the Eastern Front. Start there.

Quote Originally Posted by Polaris View Post
Search for Staline, should help ^^ I can't remember much about Russia during the WW2 but I think they didn't do much!
That has got to be the biggest understatement ever if not an all out false statement, and furthermore, Stalin was not "good." Not only were they involved with a German NAP, they helped to attack Poland (which caused the UK and France to declare war), and later they managed the Eastern Front and got betrayed by Hitler, stopped the Germans in a large number of battles, sank the most casualties and losses of all participating nations, managed to not only defend against the Blitz, but turn it all the way around. After Normandy, staying in the war caused German to be involved in a two front war; after the losses in Africa and Italy, it was a three front war. They entered Berlin around the same time as the other Allied forces and were ready to help the States with the Pacific Theater (not that Stalin wanted to do much).

If you want to move into conjecture-land, they caused the loss of the Nazi regime in WWII, and were one of the reasons for using the Atomic Bomb on the Japanese. The reason for the use wasn't to "save troop lives," it was to impress the Soviets. Tokyo and several other cities had already gotten their faces owned by fire bombs and repeated raids, along with the island-hopping strategy devised. Shortages of supplies on the Japanese part were more than enough to finish the Pacific Front.