World War I
▶ Explore on the map
World War I (28 July 1914 – 11 November 1918), also called the Great War, was a global conflict fought between the Allies, or Entente, and the Central Powers. It ranks among the deadliest wars in history, with an estimated 15 to 22 million deaths, including victims of war crimes, genocides and the Spanish flu pandemic that the conflict helped spread. The war was triggered by the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, by Gavrilo Princip in Sarajevo on 28 June 1914. Austria-Hungary blamed Serbia and declared war on 28 July; Russia mobilised in Serbia's defence, and by early August Germany had declared war on Russia and France, while Britain entered after Germany invaded Belgium. Germany's 1914 plan to defeat France quickly failed, and the Western Front hardened into a continuous line of fortified trenches from the English Channel to Switzerland. The conflict introduced large-scale industrial warfare — machine guns, heavy artillery, aircraft, chemical weapons and tanks — and mobilised entire economies and colonial empires. Its human and material cost, together with the collapse of the Austro-Hungarian, Ottoman, German and Russian empires, reshaped the political map of Europe and the Middle East and set the conditions for the following World War II.