Also without the 2nd front Russia might very well have lost in the end either way.
The russian military was a joke, specifically in terms of equipment and leadership, the old saying of pairing up soldiers 2 and 2 is true. One ran in front and when he died the other one picked up his rifle since there wasn't enough rifles to equip all the soldiers.
I can only think of two things that the russians themselves contributed with. Sheer number and the extreme bravery and will to die in battle in the defense of their motherland by the grunts.