The region was historically called Medri Bahri (Land of the Sea). Its name was changed to Eritrea following the creation of the Italian Colony of Eritrea in 1890, following the expansion of Italian occupation in the area since in 1882. The borders between Italian Eritrea and the Ethiopian Empire were defined in the 1889 Treaty of Wuchale. After Italy conquered Ethiopia in 1936 and established the colony of Italian East Africa, Eritrea became part of it. During World War II it fell under British military occupation and came under United Nations supervision in 1951. On 15 September 1952 it became the Eritrean Autonomous State, federated with the Ethiopian Empire under the sovereignty of the Ethiopian crown.