The Great War, as World War I was known until the outbreak of World War II, was the first conflict in which Australians fought under Federation, marking the first time that Australian military units had been deployed overseas. It is estimated that over 400,000 Australian men enlisted to serve overseas, representing about 39 percent of the male population aged between 18 and 44. Australia’s involvement began when Great Britain declared war on Germany on 4 August 1914. Australian troops, known as the Australian Imperial Force (AIF), participated in many of the major battles in Europe and the Middle East, including Gallipoli, the Western Front, and the Middle East campaign. By the end of the war in 1918, 60,000 Australians had lost their lives, and 156,000 had been wounded or taken prisoner.