In the past, international problems were often settled in the end by military conflict. Therefore the nations with the most powerful armies had a prominent place in the affairs of the world.
I would say that there was a changed from the Second World War, more precisely from the atomic bomb.
Since the advent of the atomic bomb, a war between great powers is likely to end in thermonuclear exchange.
Consequently, the military option has become less and less feasible due to the risk of the possibility of mutual destruction.
and so I think that today the economy has replaced military power and has become the main criterion of power. military rivalry has been replaced by economic rivalry