WWII was a matter of convenience only - the enemy of my enemy is my friend sort of thing - and both sides knew full well that the Soviets would immediately start trying to undercut the US once the Nazis were crushed and Germany surrendered. And that they did. That stretches the concept of allies beyond recognition. Furthermore, the Cold War never ended, and it's the idiots who thought it did that got us to this point in the first place. The gent who penned the book "The End of History" when the Berlin Wall fell was smoking something fierce. The Cold War only took a short haiatus when the Soviet Union collapsed and the Wall fell, sat on the back burner for a few years while we went through the increasingly tumultuous Yeltsin years, and restarted in full once Putin picked up the reins.