 The Soviet Union collapsed and the Russians, perhaps somewhat to their surprise, discovered that the captive peoples and the captive republics of the Soviet Empire didn't particularly like them. So they've had a hard time rebuilding any kind of Soviet Empire. Look at the tension between Ukraine, their nearest neighbor, and Russia. So they've not been able to rebuild the Soviet Empire, which is one reason why I don't think they will challenge the United States. They're too small.