They called it the Great War, for its size and horror. The term World War I came later, to distinguish it from WW II, which came with even greater size and horror. Neither name is accurate. By 1914, Britain had already been waging world wars for at least 250 years.
Of course early Europeans had been fighting since the first Homo Sapiens Sapiens hit the last Neanderthal on the head with a rock. With increasing food sources, skirmishes became battles. With the rise of social organization, so that armies could stay in the field longer, battles became wars. With increasing population density, the wars could become both wide spread and long lasting, but a world war could not be fought until Europe exploded across the globe as the Age of Exploration morphed into the Age of Colonization.
Portugal began it all. Spain – including Columbus – came close behind, followed by the Dutch, French and English. Exploration led to colonization, and colonies were fought over. The Dutch were early world wide colonizers, especially in the Americas and the far East. The Anglo-Dutch wars of the 1600s were primarily fought in the North Sea, but the prize was world domination. The English won, New Amsterdam became New York, and the Dutch were left dominating the Spice Islands (basically modern Indonesia).
North America was fought over for centuries by Spain, England and France. Our French and Indian War was only one theatre in the globe spanning Seven Years War, fought by England and her allies against France and hers. That conflict involved Europe, the Americas, Africa, India, and the Philippines.
The Treaty of Paris ended the war, but not the fighting. A decade later, France was again fighting the English as allies of the newly forming United States. The three way battle between France, England and Spain continued off and on through the French Revolution and the rise of Napoleon, and at every step the nations’ colonies were involved as actors or as pawns. The Louisiana Purchase, which defined America, came about because France, which had control of the territory through its control of Spain, needed to consolidate its position before engaging England, by obtaining money while getting rid of a vulnerable possession.
You should realize that I have left out innumerable wars, battles, and skirmishes to keep the size of this post in check. All this conflict was on a world wide scale, in pursuit of world wide trade. Call it World War Zero.
Needless to say, this much active history can’t pass without an accompanying literature. My personal interests are not military, but they are maritime, so I found myself caught up in the stories of “wooden ships and iron men” despite myself. I discovered Forrester’s Hornblower when I was in my twenties and read them all, several times. Hornblower is such a complex character, so full of ambition and self-doubt, that I can’t recommend him to everyone, even though he is my favorite. I would start someone new to this kind of novel with Kent’s Bolitho. He is a more normally heroic captain; I liked him quite well, but by the time I was half way through his adventures I had overdosed on the genre. Bear in mind that I had probably read all the Hornblowers three times before I discovered Bolitho, so that isn’t a criticism. For the last decade or so, O’Brian’s Aubrey and Maturin books have been widely popular. By the time they came on the scene, I had moved on, so I can only report them as hearsay.