World War I was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. More than 70 million military personnel participated, making it one of the largest wars in history. An estimated nine million combatants and seven million civilians died as a direct result of the war with losses exacerbated by technological developments and the tactical stalemate caused by trench warfare (pictured). The war is also considered a contributory factor in a number of genocides and the 1918 influenza epidemic, which caused between 50 and 100 million deaths worldwide. Unresolved rivalries at the end of the conflict contributed to the outbreak of World War II about twenty years later.Photograph: Lt. J. W. Brooke