The following outline is provided as an overview of and topical guide to World War I: World War I – major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (centred on the Triple Entente of Britain, France and Russia) and the Central Powers (originally centred on the Triple Alliance of Germany, Austria-Hungary and Italy). More than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of great technological advances in firepower without corresponding advances in mobility. It was the sixth deadliest conflict in world history, subsequentl