The First World War was a military conflict centered on Europe that began in the summer of 1914. The fighting ended in late 1918. This conflict involved most of the world's great powers, assembled in two opposing alliances: the Allies (centered around the Triple Entente) and the Central Powers. More than 70 million military personnel, including 60 million Europeans, were mobilized in one of the largest wars in history. More than 15 million people were killed, making it also one of the deadliest conflicts in history. The war is also known as the World War I, the Great War, the Imperialistic War, the World War (prior to the outbreak of World War II), and the "War to End All Wars."