The first two world wars were Euro-Centric. I don’t see another major war happening in Europe anytime soon.
Africa had a HUGE war that most of the world has never heard about.
So what you will need to get to WWIII is a well known location with some economic value.
I would put the best place for this to happen at India versus Pakistan. However without nukes Pakistan cannot hope to take on India.
India versus China isn’t likely as the Himalayas are too great a barrier to provide for anything more than small campagins and then only when during the summer months or late spring, early fall.
The Middle East presents the area most easily able to draw in countries from all over.
The Yom Kippur War proved that the USA will not let Israel be drivng into the sea, so the Arabs would have to be confident, they could take on Israel and beat it in a matter of days.
Also added to the fact is the Arabs are divided and while none of them like Israel, they don’t much like each other. Israel is a convenient distraction to have around.
North Korea is not an issue for a long term war. The North Koreans could do a lot of damage, but China knows the USA and to a lessor degree Japan will not tolerate an attack on South Korea, and would respond. China doesn’t any powerful nations near them, so the second North Korea attacks, they’d do damage, but China would likely pour in troops and over throw the government and install a regime more to their liking.
So to get to WWII, the best bet would be India versus Pakistan and throw in some nukes and then somehow get that conflict to spread west into the Middle East