After the Treaty of Versailles of 1919, Germany lost all its colonial possessions, including German New Guinea. In 1923, the League of Nations gave Australia a trustee mandate over Nauru, with the United Kingdom and New Zealand as co-trustees. Other lands south of the equator became the Territory of New Guinea, a League of Nations Mandate Territory under Australian administration until 1949 (interrupted by Japanese occupation during the New Guinea campaign) when it was merged with the Australian territory of Papua to become the Territory of Papua and New Guinea, which eventually became modern Papua New Guinea. The islands north of the equator became the Japanese League of Nations Mandate for the South Seas Islands. After Japan's defeat in World War II, the former Japanese mandate islands were administered by the United States as the Trust Territory of the Pacific Islands, a United Nations trust territory.