Napoleon attacked Russia with the strongest army in the world in 1812 and LOST.
Hitler attacked Russia with the strongest army in the world in 1941 and LOST.
Why would anyone try that again???
On the other hand, Russia has been successfully invaded several times - FROM THE EAST.
Russia has been successfully invaded from the west by Swedes, Poles and Lithuanians. Even the first Russians themselves, the Varangians, were invaders from the west.