It seems to me that there were a great deal of conflicts involving major world powers fighting in intercontinental theaters so why is WW1 considered the first? Shouldn't that title go to, say, the Seven Years war, the French Revolutionary wars or War of Austrian Succession?
Hello, this question comes up a lot and it basically comes down to the fact that there is no secret cabal of historians naming things; we name things what society names things ultimately. However there is still a lot of logic for why these people felt these two wars are exceptional enough to be called 'world wars', removed from their priors.
See this thread here for more details; I'll copy and paste the relevant bits below my TL;DR's:
TL;DR:
It's called that because people call it that; plain and simple. It has nothing to do with geography but societies perception of the events and to society, as a whole, the 7 Years' War or the Napoleonic Wars or whatever else were not significant enough / involved enough popular participation of sovereign peoples / devastated the world enough.
WWI was not called WWI at first it was called the 'Great War'; it is its association with the devastation of WWII that ultimately gave it its name as they shared a likeness. Again, not some logical sitdown of historians coining these terms...just natural evolution of terms as a whole.
WWI and WWII legitimately are, however, separated from the rest. "World War" has nothing to do with geography and everything to do with popular participation and scale and, most importantly, societies perception of those two things.
Ultimately it's hard to call "The War of Austrian Succession" a "World War" when it was a war of all European states fighting over European goals with self-identifying Europeans. The most non-Europe participant was Russia. It's hard for people to stomach calling the Napoleonic Wars 'world wars' because it's more appropriate to term them about the person at the center of them all, Napoleon, and the French Revolution itself. They weren't signified by their global presence they were signified by their incessant nature and ravaging of Europe. The Napoleonic Wars weren't world domination it was the Continental System and Spanish thrones.
One of the thought exercises I like to do is...look at the 7 Years' War or the Napoleonic Wars and just remove Europe. Go for it. What do you get? A couple of skirmishes and completely disjointed conflicts on the coasts of Africa and some significant skirmishing in North America in the former? Some commerce raiding in the latter? It hardly registers as a global event if you remove the scope of the European theater.
Do the same for WWI now. Remove the European theater; what do you get? You get millions fighting and dying in Africa across every single corner from the Indian Ocean coast to the Northeast to Egypt to South Africa to Kamerun and Portguese holdings. You go to Asia and have the Arab revolutions, the battles for Jerusalem and Gaza and generally the fall of the Ottoman Empire and the Russian Caucuses. You got the Japanese in the East Pacific and Siam all joining in on the action and, yes, small almost insignificant skirmishes on the coast of Brazil.
But yet something is still off; the Indian subcontinent and the Australian continent and the Canadians are the United States are all funneling millions of men away and mobilizing completely and willingly. Hundreds of thousands of Chinese are being sent off to workers equipped with guns and barbed wire to a far away land. Can you see my point now? You remove Europe in WWI and you can still look at just about any corner of the world and see its direct and immediate affects on a total warfare level; everyone was getting in on the pie. Can you do the same for any other war before it? No, not without some serious mental gymnastics.
Relevant quotes from above link:
Another reason, and perhaps the most common modern justification though, is that those wars were European wars which just extended to their colonies which happened to be overseas. They weren't 'global' conflicts in that respect they were localized conflicts with localized goals which just had extended fighting -- every single war you listed fits that bill. Outside of the Mughal Empire in the 7 Years' War they're all European powers. The First World War was the first truly global war which hit every single continent. Japan and China and East Pacific colonies, India, Australia, South, East, North, and West Africa, Eastern Europe, Western Europe, the North Sea, Brazil, Central America, North America. Every single corner of the Earth, all from independent or quasi-independent dominions (Australia, Canada, South Africa, New Zealand) operated as independent military entities and as independent government actors. That had never been done before, ever.
You wouldn't call the Gulf War a 'world war' even though it was the U.S. & Friends (America & Europe) vs Iraq (Asia), would you? It had global participants, significant casualties, etc. It's the same thing here honestly: None of those wars you linked involved the popular participation of everyone everywhere even though they, at times, involved some powers from not-Europe and fighting in not-Europe. A 'world war' is not just who is fighting but scale. No one was unaffected by WW1 or WW2. Yes it was started in Europe but its participants not only went beyond Europe those directly and largely affected were as well. 1.5 million Indians would volunteer to fight, America drafted nearly 3 million people, 40% of the Australian male population would enlist, fighting would occur off the coast of Brazil and just about all of Central and South America would come on the side of the Allies as independent, sovereign states. China would send tens of thousands of men to contribute to trench building and also providing supplies while Japan seized numerous German colonies in the Pacific in blatant expansionism. Africa was a theater of independent, quasi-independent, and European fighting forces that raged throughout the war.
But really I like the reply I said to someone who replied to me as I think I put it even better there:
Most importantly: World War One was not called World War One at the time. It was called the Great War for a reason; the people at the time recognized its superior level of involvement and scale but did not call it a world war at the time. That title only came after WW2 and people looked back and said, man, that 'Great War' really wasn't all that different from this albeit just a slightly smaller scale.
And that's what happened. People saw the devastation of WWII; they saw the popular involvement of everyone everywhere like the Indians and the Australians and the Canadians and the Americans fighting literally across the globe and the Germans and the Chinese vs Soviets and so on and so on and they looked back and saw WWI was a pretty similar picture. Those international belligerents like Australia and Canada would find their national identities in WWI and can directly attest that to said independence. Instead of the Pacific Theater, Mediterranean Theater, and Western Front, and Eastern Front as the significant fronts in WWII they had the Western Front, Eastern Front, Mediterranean Front, Middle Eastern Front, and sub-Saharan African front as the significant fronts.
. . .
Unlike the wars before it, and this bears repeating, it wasn't just a couple of colonial conflicts or one or two sovereign non-European states partaking. It was everyone. China, Japan, India, Australians, Siamese, Rhodesians, South Africans (Boers), Togo's, Palestinians, Arabs, Russians, Germans, and Americans would all send men with distinct identities into the fray for their own goals and their own motivations and their own whims.
It was, truly, a scale unseen before and the level of shoehorning that must be done to compare earlier wars to it is really high. Yes it's a highly arbitrary thing that society has imposed upon it and yes, WWI is given that title because of its direct connection with WWII largely, but it's not unfounded. I have nothing short of tomes behind me on the oft-called 'first world wars'; the 30 Years' War, the 80 Years' War, the 7 Years' War, the Napoleonic Wars, even the Dutch-Portugese War and the scale was just never on the scale of WWI or WWII in any of these wars.
And for repetitions purpose:
It has nothing to do with geography and all to do with popular participation and scale; no stone went unturned and corner untouched in WWI or WWII; everyone was directly impacted by it and every corner of the Earth can remember directly sending combat troops or being materially affected for this conflict in a sovereign manner. 1.5 million Indians would volunteer, millions of British commonwealth, millions of Africans would tear across sub-Saharan Africa in war and the Middle East would tear itself apart from revolution against the Ottomans and the Japanese started to build the foundation through this war for the empire that would join the Axis 25 years later. This type of scale, in any of the works I've read, was never reached.