Italian East Africa (Italian: Africa Orientale Italiana, or AOI) was a short-lived (1936-1941) Italian colony in Africa consisting of Ethiopia (recently occupied after the Second Italo-Abyssinian War) and the established colonies of Italian Somaliland and Eritrea held in the name of Victor Emmanuel III of the Kingdom of Italy. In August 1940, British Somaliland was conquered and annexed to Italian East Africa.
The other Italian colony in Africa was Italian North Africa (Africa Settentrionale Italiana, or ASI).
Rule in Italian East Africa (Ethiopia, Eritrea, and Italian Somaliland) was harsh for the native peoples, especially towards Ethiopians as Fascist policy sought to destroy their culture. In February 1937, following an assassination attempt on Italian East Africa's Viceroy Rodolfo Graziani, Graziani ordered Italian soldiers to raid the famous Ethiopian monastery Debre Libanos where the would-be assassins had briefly taken refuge and had the monks and nuns in the monastery executed. Afterwards, Italian soldiers pillaged native settlements in Addis Ababa, which resulted in hundreds of Ethiopians being killed and their homes left burned to the ground.
Fascist colonial policy in the AOI had a divide and conquer element. In order to weaken the Orthodox Christian Amhara peoples who had run Ethiopia in the past, territory claimed by Eritreans and Somalis was given to the provinces of Eritrea and Somalia. Reconstruction efforts after the war in 1936, were primarily focused on benefiting the Muslim peoples in the AOI at the expense of the Amhara to strengthen support by Muslims for the Italian colony.
Italy's Fascist regime encouraged Italian peasants to colonize the AOI by creating agriculture there. However few Italians came to the colony. By 1940 only 3200 farmers had arrived, less then ten percent of the Fascist regime's goal. Continued insurgency by native Africans, lack of resources, rough terrain, and uncertainty of political and military conditions discouraged development and settlement.
The colony proved to be highly expensive to maintain, the AOI's budget in 1936-37 requested from Italy 19.136 billion lire to create the necessary infrastructure for the colony. At the time Italy's entire revenue that year was only 18.581 billion lire.
In June 1940, at the beginning of Italy's involvement in World War II, the AOI potentially constituted a dangerous menace to British interests in Africa. From one perspective, a successful Italian attack from the colony through the Sudan and the establishment of a connection to Italian-held Libya would have isolated vital British positions in Egypt and the Suez Canal. However, from a different perspective, the colony itself was isolated from Italy and surrounded by British forces in the Sudan, Kenya, and British Somaliland. British forces in Aden could provide critical air and naval support against Italian naval forces operating in the Red Sea. Italian maritime transport was cut off by the British at the Suez Canal. What supplies did arrive in the AOI were generally from the air and in small quantities.
At the beginning of the East African Campaign, the Italian troops amounted to 291,000 men including native troops. Training of the native troops was poor, the Italian garrisons were too spread out, due to the extremely poor state of roads, and were essentially reduced to a static role without enough ammunitions and oil reserves (which allowed the Allies to liberate AOI in 1941).
In 1940, the adjacent protectorate of British Somaliland was occupied by Italian forces and absorbed into Italian East Africa. The conquest was the only victory of Italy, without reinforcement from German troops, during WWII against the Allies. This occupation lasted around one year.
On March 27, 1941 the stronghold of Keren was captured by the British troops after a strenuous defence from general Orlando Lorenzini. After the surrender of Massaua (April 8), Eritrea was lost for Italy. The war was lost on May 1941, when the last stand on Amba Alagi under Viceroy Amedeo di Savoia, Duke of Aosta, at Amba Alagi ended honourably in face of overwhelming Allied troops. November 28 of the same year, general Guglielmo Nasi and the last Italian occupants of Gondar surrendered.
Many Italians fought a guerrilla war in the "Africa Orientale Italiana", after the surrender at Gondar of the last regular Italian forces in November 1941. From November 1941 to September 1943 there was an Italian guerrilla force made up of 7000 Italians who had not accepted surrender to the Allies. They were waiting for the possible arrival of the Italo-German army of Rommel from Egypt and the Mediterranean (called in 1942 by Mussolini "the Italian Mare Nostrum"), but after the Battle of El Alamein the momentum of this resistance slowly faded away.