Summarize World War I.

World War I, also known as the Great War, was a global war centered in Europe that lasted from July 28, 1914, to November 11, 1918. It involved many of the world's great powers, which were divided into two opposing alliances: the Allies (originally the Triple Entente of France, Russia, and Britain) and the Central Powers (originally the Triple Alliance of Germany, Austria-Hungary, and Italy). The immediate cause of the war was the assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist in June 1914, which set off a chain of diplomatic clashes and mobilizations that escalated into full-scale warfare.

The war saw unprecedented levels of destruction and loss of life due to new military technologies and the nature of trench warfare. Battles like Verdun, the Somme, and Passchendaele became synonymous with the carnage and futility of the conflict. The war also marked the first use of chemical weapons and the massive participation of countries from outside Europe, including troops from Australia, India, Canada, New Zealand, and the United States, which entered the war in 1917 and helped tip the balance in favor of the Allies.

By the end of the war, four major imperial powers—the German, Russian, Austro-Hungarian, and Ottoman Empires—had been militarily and politically defeated and ceased to exist. The maps of Europe and the Middle East were redrawn with several new independent nations emerging. The Treaty of Versailles, signed in 1919, officially ended the war but imposed heavy reparations and territorial losses on Germany. This treaty and the economic instability that followed contributed to the rise of fascism in Europe and the eventual outbreak of World War II.