World War I was called “The Great War” before World War II because people did not think there could be a repeat of the idiocy that reigned in Europe from 1914-1918. It started in Europe in August 1914 as a result of the June 28, 1914 assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian Empire, by Gavrilo Princip, a Serbian anarchist and member of the Balkan separationist group, the Black Hand. Princip said, “I am a South Slav nationalist. My aim is the union of all Yugoslavs, under whatever political regime, and their liberation from Austria by terrorism.” (Jennings and Brewster, The Century, p.53.) Austria-Hungary blamed the Serbian government for the assassination.
Europe at the time was a house of cards; competing alliances that were formed to maintain the balance of power and to keep peace. On the one hand, England and France joined with Russia (known as the Triple Entente or “Allies”) and, on the other hand, Germany joined with Austria-Hungary and Italy (known as the Triple Alliance or “Central Powers”). Italy backed out of its treaty obligations to Austria-Hungary on the grounds that its partners started the fighting, and it only had the duty to come to their defense if they were attacked. Italy eventually joined the Allies in 1915. The Ottoman Empire (Turkey) and Bulgaria joined the Central Powers in 1915 and the United States and Japan joined with the Allies in 1917. (See generally, Tuchman, The Guns of August.)
After Princip killed the archduke, Austria-Hungary made harsh demands on Serbia, taking the position that if its demands were not met, there would be war. Russia, because of its treaty obligations with Serbia, answered Austria-Hungary’s threat by stating it would come to Serbia’s defense if it was attacked by Austria-Hungary. Russia’s threat caused Germany to step into the picture. Germany, based on its treaty with Austria-Hungary, took the position that, if Russia fought Austria-Hungary, it would come to Austria-Hungary’s aid. The cards kept falling when France indicated that it would come to Russia’s aid if Germany became involved. And, the whole house of cards collapsed when Great Britain honored its treaty obligations to help Belgium, which was invaded by Germany.
Ironically, despite the number of combatants ( more than 70 million military personnel, including 60 million Europeans from more than a dozen nations, were mobilized) and the nature of newly developed weaponry (fully automatic machine guns, flamethrowers, submarines, tanks, artillery, poison gas including chlorine, phosgene, mustard and other chemical weapons, airplanes, etc. (Stout, Coming Out of War, Poetry, Grieving and the Culture of the World Wars, p. 3), few people thought the conflict would last more than a few months. A popular expression at the time was: “They (the soldiers) will be home before the leaves fall.” (Tuchman, The Guns of August, p. 133)