[dirtyid]

Pinker's "long peace" theory with respect to global conflict is likely bad statistics - 20th-21st century under US military hegemony had a comparable if not higher number of conflicts, see Max Roser’s work documenting global conflicts over the past 600 years. What has changed is that war now is generally shorter and less deadly especially towards combatants, but that's more reflective of the pace of modern war enabled by modern weapons. High intensity wars don't last for 20+ years anymore because you can pretty much destroy nations in 1-5, and belligerents are quicker to exhaust and forced to settle. In aggregate war fatalities is down, but not # of conflicts. US hegemony didn't stop USSR and RU from warring in their periphery, nor PRC border skirmishes pre 90s when US had vast more naval power asymmetry. When countries want to fight for their interests, especially regional, they still do.

Ultimately, US military dominance is good for US+LIO interests / serenity, but hard to extrapolate anything more. IMO multipolarity will increase the chance of "smaller" conflicts as poles assert their own interests for sure, but it's going to be around the baseline of conflicts that's consistently been simmering throughout history. The fear is increasing large-scale conflict between poles/blocks - ending the cyclic gap between major wars among major powers - but that's what happens when declining hegemon pushes their interests to the exclusion of others too intensely for too long.