What would the next major war look like?

China overcomes usa in gdp, imposes global changes in traditional western-eastern economic interest camps, USA can't stand this and fires up proxy wars to supress china's expansion as well as more intense cyberattacks to their infra.

Then comes what every major war has brought. Chaos, deaths, misery, economic shuffles. The only thing that changes are the means and key actors.

An idiot takes charge of the worlds Hegemonic Power, does a bunch of destabilizing things, and bullies a near peer one too many times for stupid reasons.

At this point, either said idiot is summarily publicly removed from power by cooler heads, or nuclear weapons are loosed, and we all lose.