In October 1935 Italian dictator Benito Mussolini invaded Ethiopia. The poorly equipped Ethiopian armies were defeated in the war that ensued. Italy formally annexed Ethiopia, along with Eritrea and Italian Somaliland, to form Italian East Africa in May1936. Guerilla warfare continued in Ethiopia under Italian rule. When guerrillas tried to assassinate the colonial viceroy in 1937, the Italians killed thousands of Ethiopians in retaliation. In 1941 Ethiopian and British troops liberated Ethiopia and restored Emperor Halie Selassie to the throne. The following year Ethiopia declared war on Italy, Germany, and Japan. In 1945 Ethiopia became a founding member of the United Nations.