I read a book written in the 90s shortly after the end of the Cold War that made an argument that everything from 1914 to 1990 should just be declared “The Greatest War” or something along those lines because technically we did just fight two massive wars and a bunch of smaller wars entirely due to events started in 1914.
I’ve seen the argument made that the “world” war started in December 1941 because the Japanese and German declarations of war against the United States brought all of the major world powers of the time into the fight and united what had been separate regional wars into a single global war.
That said, I’ve also seen the argument that the first world war was fought between 1754 (or 1756) and 1763. What’s generally called the Seven Years War was also a global conflict involving all of the major powers of its era.
Really, it’s all just an extension of a domestic violence incident involving the sons of Adam and Eve.