Probably nations that belong to the one God. The hebrew prophecy, the islamic prophecy and the christina prophecy say that the end all of them will reunite under one God and fight in a last war versus all disbelievers, so mainly versus Asia.
Especially nations like India and China even as the most populated nations on this planet are at high risk to be destroyed in the future, because they are those who do not follow the one God. And the Chinese call themselves the sons of the Dragon and so are flagged as enemy.
If you read in Moses 5.20 there is the law of war from the one God already adressing how will be fought.
We western nations are very advanced, so a third world war will not be fought with normal soldiers, but with technology as we already have seen in Afghanistan and Iraq.
If it comes then to a real world war with the use of weapons of mass destruction, then it is very likely that bio technological weapons, race destruction wapons, will be used to simply to wipe out a complete continent that has other genetic.
After a few months the war would be over. Birds or other animals would carry in the viruses.
This is better than nuking, because the land then can be used after the war is over and mankind united.