World War I

World War I, or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers. One of the deadliest conflicts in history, World War I resulted in an estimated 15 to 22 million deaths, including those in war crimes and genocides. The war also helped spread the Spanish flu pandemic. The conflict saw important developments in weaponry, including the first large-scale use of machine guns, artillery, aircraft, chemical weapons, and tanks. The causes of World War I included the rise of the German Empire, which disturbed the long-standing balance of power in Europe, and the exacerbation of imperial rivalries, as reflected in new alliances and an arms race between the great powers. Tensions in the Balkans reached a breaking point on 28 June 1914 when Gavrilo Princip, a Bosnian Serb, assassinated Franz Ferdinand, the heir to the Austro-Hungarian throne. Austria-Hungary blamed Serbia and declared war on 28 July, upon which the Russian Empire mobilised in Serbia's defence. In early August, Germany declared war on Russia and France; the United Kingdom entered the war after Germany invaded Belgium. Germany's strategy in 1914 was to quickly defeat France, but its advance was halted in September, and the Western Front solidified into a near-continuous line of fortified trenches from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. The Ottoman Empire joined the Central Powers in November, which was followed by a failed Allied campaign at Gallipoli. Japan and Italy also joined the Allies. Major battles, including those at Verdun, the Somme, and Passchendaele, failed to break the stalemate on the Western Front. In April 1917, the United States joined...