If the Russians commit to an attack south of there border, that would be very stupid for them. Hitler was always going to invade, and after the fall of France, and the soviets push far enough south to attempt any immediate reinfocement of there troops, the germans attack. With there thin lines and no army due to the turkish invasion, as well as the troops stationed on the border of manchuria, ther Germans role over them, destroying many of there troops, making the invasion of russia that little bit easier. As well as if the ally with all the countires you mentioned, I think Russia would fall.

__________________
They shall grow not old as we that are left grow old Age shall not weary them, nor the years condemn
At the going down of the sun and in the morning
We shall remember them. Lest We Forget