In the history of golarion I don't see a ww of nation's, if you where an official writer of Pathfinder which nation's you Will put in the war as an ally and which one as an axis
My axis: chelexia, nex, belkzen.
My ally; taldor, andoran, mendev.
If I were an official writer, I wouldn't forcefully try to put a World War where it doesn't belong. You cannot really have a World War if you don't have empires stretching the whole world, and most countries don't have oversea colonies, the colonization era is barely starting. Even on local scale, the countries are diverse and have little to do with each other (except for trade, maybe), so grand coallitions are unlikely. There's just no potential for a truly global war yet. That's why most wars are 1-on-1, or 1 vs many, and such wars were present, like Chelish Everwar or the Shining Crusade.
If you want a big war in the current political climate, it could start with Cheliax attempting to reconquer all its previous territories, and these countries forming a coalition. That would include Andoran, Galt, Molthune and Nimrathas (common threat could make theses two fight on the same side, for a change). Cheliax would bring its own vassal states, Isger and Nidal. If Talfor decided it's a good idea to get involved against Cheliax, Cheliax could entice Qadira to fight Taldor to distract them. In return, Qadira wants Cheliax's help to reconquer Osirion.
I don't really sea a reason why other coutries would join either side. Varisia is too underdeveloped. Belkzen could take an opportunity to attack Nimrathas, but they would do it on their own accord, not allied with Chelaxians. Thay could involve Lastwall, but they would fight specifically to hold off the orcs, not against the Chelaxians. Druma and Kyonin would prefer to remain neutral. Other countries are too far to care.
So we have, on one side:
Cheliax, Isger, Nidal, Qadira
and on the other:
Andoran, Galt, Molthune, Nimrathas, Taldor, Osirion
Multi-nation wars need a few things to get going as I understand it. Alliances which call in other nations when one is attacked. A means of getting large numbers of troops across the distances involved and keeping them supplied. And leadership with no fear of the consequences of a huge war (where the other side might crush them if their allies abandon the field), or at least a prize to be grasped which outweighs those consequences.
Do all these conditions exist in the nations you've named? I don't know enough about Golarion to say.
While it doesn't make a lot of sense, it would be pretty cool.
The tricky part would be coming up with a competing pair of multinational alliances that can turn a small war between two neighboring nations into a conflagration that embroils most of Avistan. The problem I keep running into is that I can't work out what the alliances would be, as the setting contains numerous pairs of natural enemies but few if any combinations of natural allies.
The solution might be simpler than expected. Many of the 6th books in an AP have a "what if the PCs fail" section, describing the rise of an evil faction, who joins them and who resists.
I think that might make a better fantasy World War than trying to emulate real world politics in Golarion.
The biggest fights I can think of is that between Geb and Nex, which created the Mana Wastes and Earthfall by the aboleths.
/cevah
A means of getting large numbers of troops across the distances involved and keeping them supplied.
In a setting where one wall of fire can royally **** up a charging army, I've always thought that mass combats would be a lot more... interesting.
A means of getting large numbers of troops across the distances involved and keeping them supplied.Magic.
I'm not sure all nations have 17th+ level wizards/18th+ arcanists (or 18th+ sorcs with appropriate spell selections) at their beck and call.
A kingdom could probably afford a few high-level scrolls. It's cheaper to teleport a small army than to supply it on a four hundred mile march.
The real problem, as I see it, is every country seems to have a lot of problem elements that if there were to be a significant war effort to happen between several nations you would likely have a lot of "evil" groups take advantage of the relative power vacuum to freely commit a lot of nefarious acts.
The solution might be simpler than expected. Many of the 6th books in an AP have a "what if the PCs fail" section, describing the rise of an evil faction, who joins them and who resists.
I think that might make a better fantasy World War than trying to emulate real world politics in Golarion.
Are there any particular APs whose failure conditions result in reasonably large "evil" alliances?