World War I or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously described as the "war to end all wars", more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history.

An estimated nine million combatants and seven million civilians died as a direct result of the war, while it is also considered a contributory factor in a number of genocides and the 1918 influenza epidemic, which caused between 50 to 100 million deaths worldwide. Military losses were exacerbated by new technological and industrial developments and the tactical stalemate caused by gruelling trench warfare. It was one of the deadliest conflicts in history and precipitated major political changes, including the Revolutions of 1917–1923, in many of the nations involved. Unresolved rivalries at the end of the conflict contributed to the start of the Second World War about twenty years later

Source - Wikipedia