Geo-politics today do not include war, at least no the war that we all know of, with soldier on foot and even trenches.
War in the 21st century is all bout spheres of influence and economy, no one wants to go to war now because none of them will reap benefits from it.
If china goes to war in North Korea there are many things that will hapen such as
1.Massive migration of refugees
2.Possible expansion of USA sphere of influence in the region
3.A union with South Korea that will burden the nation with investing in the region, as seen when the Berlin Wall came down and west Germany had to invest massive in the east so that it did not get left behind
All these war games are intimidation tactics if you ask me, to flex the muscles and make the other go in submission seeing they have no chance of winning
Just my 2 cents here, but there is a lot to speak about