These days we are hearing in a way we have not in a long time reference to "World War Three"--with
many speaking of the Russo-Ukrainian War as potentially such a war, or, like Emmanuel Todd,
telling us such a war is already ongoing. However, in judging such claims, which are hugely significant for how we see the world, it is necessary to consider just what one means by "World War Three"--figuring out which requires us to think about just what is a "World War."
It seems to me fair to say that a world war means a war which meets two requirements:
1. The war is "systemic" in nature. That means that the principal actors in an international system are belligerents in a conflict with system-level stakes--that virtually all the great powers are fighting with the prize going to the victors the dominance of the system. This means that they have scope to realize major goals to which others might be opposed (like claim a larger sphere of influence), or even make the rules for the system (like how the international economy is to be managed).
2. That system in question is a world-system, rather than a merely regional one.
In considering these requirements take that that favorite example of scholars of International Relations, the Peloponnesian War fought among the ancient Greek city-states in the late fifth century B.C.. To the extent that the alliances led by Athens and Sparta pretty much encompassed that system, while the Persian Empire ruling pretty much the rest of what to the Greeks was the "Known World" eventually came into the conflict, one could call it a systemic conflict. But this clash in a portion of the eastern Mediterranean was a far cry from a planetary-level conflict, as were all the other conflicts of ancient and Medieval times (colossal as some of them, like the wars of Chinese unification and reunification, appear even by today's standards).
The possibility of a system on a world scale, and thus wars on a world scale, only really emerged with the spread of the Western colonial empires from the fifteenth century on. Already in 1478 Spain and Portugal were in a position to fight a sea battle in the distant Gulf of Guinea, and the possibility, and actuality, only grew from there with their conquests in the Indian Ocean and the Americas seeing European battles in those places in the sixteenth century. Indeed, a conflict like the Nine Years' War (1688-1697) saw the participants in a predominantly West European conflict (mainly the French, Dutch, English, Spanish and Holy Roman Empires, fighting over essentially local issues) battling each other as far afield as North and South America, the Caribbean, West Africa and India, and on the basis of the results, dividing and redividing the world.
Of course, to say that these powers fought battles
around the world is a different thing from saying that these battles were fought in wars
of the world--those distant clashes still typically highly localized episodes between powers whose positions were limited and by no means secure in those places, and relatively minor in the life of those faraway regions, certainly next to their own local conflicts. Indeed, as eighteenth century historian Jeremy Black argues in
Rethinking Military History, even as inter-European clashes in Indian waters and on Indian soil became increasingly regular and significant "the Mughal conquest of the Sultanate of Delhi in the 1520s, the Persian invasion in 1739–40 . . . and that of the Afghans in the 1750s" were and remained for a long time after "more important . . . than European moves." Likewise, Black reports, the rulers of eighteenth century China were much more concerned with the Dzungars than the European powers with which they had already clashed over the Amur Valley and Formosa (both of which China recovered successfully in the seventeenth century). And so forth.
However, as the colonial empires went on getting bigger and more powerful and more secure, and technology enhanced not just their connectivity but their reach (with railroads, steamships, telegraphs) those conflicts grew not only in extent but in the intensity with which they were waged, such that one could think of the war that broke out among them in 1914 as truly a "world war." Involving as it did the Austro-Hungarian, Serbian, Russian, German, French, Belgian and British governments from its first three days on, this automatically embroiled polities controlling over half the world's territory and population. Shortly afterwards the Ottoman Empire, Italy, Japan, the United States and China, among many more, also joined in, with the result that nearly all of Eurasia, Africa, North America and Australasia involved. Of the major world regions only Latin America was left out to any significant extent, though it should be remembered that in 1917 the proposal of a German alliance with a Mexico in which U.S. troops were intervening (the "Zimmermann Telegram") played a part in drawing the U.S. into World War I, while shortly after the U.S. entry South America's largest country, Brazil, also officially entered the war on the side of the Allies. The result was that nearly all of the world's people lived under governments actively fighting in the war, while the war across semi-colonized territories like China before its entry into the conflict, and the fighting at sea, the economic dislocations the fighting entailed, and much else, meant that very little of humanity was untouched by the war in one way or another. Moreover, that war's consequences were vast, with several empires (not least the Austro-Hungarian, German, Ottoman, Russian) broken up, control of much of the world transferred from one power to another (as with the new empires Britain and France carved out of the old Ottoman territory), and efforts made to set up new arrangements for dealing with the world's problems (like the League of Nations) as Germany's aspiration to world power was defeated (to the point of Germany being shorn of its colonies, its homeland reduced in size, its economy burdened with reparations and its government disarmed) and Britain remained (officially, at least,)the leading power, while the U.S. became a significant factor in European affairs in unprecedented fashion. World War Two was, if anything, even more global than the first in its participants, and its impact on the world's life--ushering in the U.S.-led world order we have now, with its currency and trading arrangements (the U.S. dollar as the principal currency of international trade in the open system ushered in by the General Agreement on Tariffs and Trade), institutions (the United Nations, the World Bank, the International Monetary Fund, the U.S.-led network of military alliances like NATO) and much else.
But what about the wars since? Certain observers, especially of the neoconservative bent, characterized the Cold War as "World War Three," and the post-Cold War conflicts against terrorists, "rogue states" and other such parties "World War Four." Still, that said more about their eagerness to mobilize the public behind the most extravagant pursuit of those conflicts than it did the reality of those wars. If for the citizens of China, Korea, Indochina and other places the Cold War did not stay cold locally--indeed, millions dying in wars that were localized but as intense and brutal as any that had ever been fought--it was never a matter of full-blown war at the systemic level. And conflicts with terrorist groups, disparate states and the rest were far too diffuse a thing to really be considered a coherent conflict. It was also too far removed from the level of the system--as the great powers were not really opposing each other here--for the idea to stand up to scrutiny.
As a result World War Three remained for most observers the war yet unfought.
Of course, if you have read this little lesson in "IR" up to this point you were probably hoping that I would say something about what to make of the current conflict, rather than just treating the theoretical side of the matter, and I will not disappoint you here. Today's great power list includes, at a minimum, the U.S., Russia and China, with Japan and the major European powers (Germany, France, Britain, collectively, at least), and India, also having claims. The current war may be said to involve nearly all of these actors in the conflict in Ukraine to some degree--with Russia fighting a Ukraine whose backing by the U.S.-led, Europe-including NATO alliance is massive and escalating--while Russia has its partnership with China. Meanwhile the conflict of the U.S. and Japan and India with China is similarly intensifying.
It seems to me that NATO's war with Russia escalating to a significant commitment of forces to Ukraine's side in direct contact with their Russian counterparts would at least put the war into World War III territory. The conflict's "World War III" status would become absolutely unambiguous were the European conflict to become linked with China's conflicts with the U.S., Japan and other regional actors, either through China's support of a Russia fighting NATO, or an outbreak of fighting in East Asia itself, a hardly unprecedented development--world wars, after all, typically becoming world wars not on the first day, but as other actors initially outside them find themselves compelled to participate, and differing conflicts merge together in the process. (Initially Germany in northern Europe, Italy in the Mediterranean and Japan in East Asia pursued their imperial ambitions apart from each other. It was only after the fall of France in 1940 that Italy threw its lot in with Germany, and in 1941 that the German attack on the Soviet Union, Japan's attack on Western possessions in Asia and the western Pacific, and the subsequent round of declarations of war, tied the Asian and European conflicts together into one big conflict between the U.S.-British-Soviet-dominated Allies and the German-Italian-Japanese-led Axis.)
By contrast in the absence of direct, large-scale hostilities between great powers the issue becomes much more ambiguous. Just how do we read NATO's present, not potential or even likely but actual-at-this-moment provision of aid to Ukraine? How do we read China's backing of Russia now? That is what determines whether we continue to think of World War Three as a significant possibility--or whether, as Todd argues, the conflict as already begun. With even the most basic facts of the matter incomplete and much disputed, I have to admit that there seems to me room for the kind of argument here. However, there is no argument whatsoever about the fact that, if we are not already seeing World War III we are closer to it than we have ever been since the 1980s, and maybe even since 1945.