The War to End All Wars is a four page article about real world history, as it connected to the adventures of Indiana Jones. Written by Kurt Busiek, it was published at the end of the issue #5 (the first half of "Verdun, September 1916") of The Young Indiana Jones Chronicles comic series in June 1992, accompanying the events of the comic.
The article focuses on World War I, called at the time, "The Great War" or "The War to End All Wars". Causes for the war's level of death and destruction included major changes in Europe since the last major war, including greater population levels, the rise of nationalism, changes in warfare technology, including the development of barbed wire and the machine gun which shifted the advantage to the defender, and the system of alliances that would change a small war into a large one.
Austria-Hungary (allied with Germany and Italy) and Russia (allied with France and Serbia) were both looking at the Balkans for expansion, as they were slipping out of control of the Ottoman Empire. The 1914 assassination of Archduke Franz Ferdinand, heir to the Austrian-Hungarian throne, by Serbian terrorists while in Austrian-annexed Bosnia triggered Austria-Hungary into starting a war against Serbia at the end of July. Unwilling to back down like they had when Austria-Hungary had annexed Bosnia in 1908, Russia joined with Serbia, and called upon its French allies. Knowing that it would have to fight on both the east and west, Germany decided to fight France first then focus on the slower-to-mobilize Russia. Bypassing the French defense lines on their border, German forces swept through neutral Belgium to invade France, which triggered the British to join the war in August as Britain, Germany, and France had previously made a treaty guaranteeing Belgian neutrality.
Colonial possessions got swept into the war, with Japan (allied with Britain) trying to snap up Germany's possessions in the Pacific before Australia and New Zealand could do so. The Ottoman Empire secretly allied with Germany to win back some of its lost land, and thus began to fight Russia and Britain. British-allied Portugal was sidelined until 1916 in order to overthrow a pro-German coup. The Allies played the Central Powers off each other, getting Italy to switch sides in 1915, and picking up other latecomers.
When the war started, the United States of America had remained neutral despite offers from both sides, and strong sentiments for France, Germany, and for and against Britain. Growing sympathy for the Allies through propaganda, economic benefit, and eventually German submarine attacks on commercial shipping helped to push for siding with the Allies, but the discovery of the Zimmerman telegram, an intercepted message from Germany offering US lands to Mexico if they joined the war, and the subsequent sinkings of American ships caused a US declaration of war against Germany in April 1917.
The final effect of the war was the high level of death, destruction and expense, such as seen at the Battle of Verdun, that even the victors suffered through concessions to their subjects that led to the weakening of the European empires, including the Russian Revolution. Before the war, a war on that scale had been deemed "impossible" because it was too expensive. But after nine million casualties, it showed that things that "just can't happen" sometimes do happen, sometimes for very little reason.