Xi, Putin
Russia's President Vladimir Putin (C) reviews a military honour guard with Chinese President Xi Jinping (L) during a welcoming ceremony outside the Great Hall of the People in Beijing on June 8, 2018.
  • For decades, the US has been the world's main military superpower. 
  • But the US faces formidable new threats, and rising global conflict. 
  • In the wake of the Ukraine war, Russia and China have been growing closer. 

For decades, the military might of the US was unchallenged.

After the collapse of the Soviet Union in 1991, the US was the world's only military superpower, with its forces deployed all over the world to defend allies and deter aggression.