Essentially its the idea that the interaction between an incumbent power and rising "challenger" power inevitably leads to war between the two. I was expressing my hope that if this does happen, the war can play out in less destructive arenas - one of which is in the competition for reserve currency status which the US has held for the whole of the modern era. This article possibly points at China's first shots in this conflict.

Edit: credit LarsDu88 for correcting me on its age. I originally stated the idea was very old (2.5k years) but actually its a recent idea based on an ancient conflict between Athens and Sparta

President Xi of China mentioned it when the US President visited him in May.

https://www.hks.harvard.edu/faculty-research/policy-topics/i...

Rising power challenges the fading imperial hegemony. In this case, CNY displacing USD.