The Italians never forgot the defeat at Adwa dealt to them by the Ethiopians. Upon Mussolini taking over in Italy, he was bent on getting revenge. Italy was in a strategic position to invade Ethiopia; they had already established Eritrea and Somalia as colonies.
French support, which had been vital in keeping Ethiopia from being colonized, began to wane during the 1930s (Pankhurst 222).
The Italian invasion was sparked by an incident that occurred in the town of Wal Wal inside of Ethiopian territory. In November of 1934, an Ethiopian force clashed with an Italian force that was illegally in Ethiopian territory. Italy demanded reparations and an apology. Haile Selassie instead took the matter to the League of Nations. Mussolini did not wait for the League to rule and began the invasion of Ethiopia on October 3, 1935. On November 18, the League placed sanctions on Italy but it omitted the export of oil, which would have been a major damper on the Italian campaign (Pankhurst 223-8).
The Italian campaign started from Eritrea. On the first day of the invasion the Italians 'symbolically' bombed Adwa. By October 15 they had taken Aksum and 3 weeks later Maqale. Over the next few months, using aerial attacks and mustard gas, the Italians slowly marched southward through Tigray, defeating one Ethiopian army after another. By April, the Italians had defeated the last major Ethiopian army in May Chaw. They took Addis Ababa on May 5 (Pankhurst 226-235).
Haile Selassie left Addis Ababa on May 2 and he made his way to England, where he was given asylum. He traveled to Geneva on June 30 to address the League, however the League decided on July 4 to end the sanction against Italy. Italy merged Ethiopia with Eritrea and Somalia to create Italian East Africa. This move was recognized by most nations of the world.
The Italian occupation lasted until 1941. The five year occupation had both positive and negative affects on Ethiopia. The Italians put extensive effort into road building. They upgraded some parts of Addis Ababa; they put an electric grid in the section of the city that was heavily populated by their own citizens and built a dam to increase the supply of water. However, Addis Ababa had been segregated and the intermixing of races was forbidden (Pankhurst 239-240).
The darkest period of the occupation occured in February 1937. As assassination atempt on the life of the viceory led to three days of revenge killings in Addis Ababa that left thousands of innocent Ethiopians killed. The crimes were committed by the Italian civilian population and was stopped only when their military got involved. However, over the next few months, the military would go on to kill thousands, mostly targeting the nobility and the educated, fearing they could rebel against them. Hundreds of monks and deacons were also killed, after being susptected in conspiring with the assassination attempt (Mockler 174-181).
The Italians occupied Ethiopia but they never were able to truly turn it into a colony. Resistance amongst the people was rampant and patriot forces made it extremely difficult for the Italians. Many failed attempts at retaking Addis Ababa was made by patriots forces but were always crushed because the Italians had aerial superiority. The Italians had taken most major towns but a good portion of the Italian army was forced to live in forts (Pankhurst 243-245).
The turning point in the occupation was the beginning of World War II. Mussolini declared war on France and England on June 10 of 1940. This event forced England to rethink her position of neutrality in the Ethiopian-Italian struggle. The Italian East Africa, which now included Ethiopia, posed a serious threat to British colonies in the area; Sudan, Kenya and Egypt. England then chose to come to the aide of the patriots forces. They flew in Haile Selassie to Sudan on June 23. On January of 1941 three British forces, from Sudan, Kenya and Eritrea began the attack. The attack was very successful; they took Addis Ababa within three months. The Sudanese force that accompanied Haile Selassie entered Addis Ababa on May 5 1941, exactly 5 years after the Italians took Addis Ababa. The last battle of the war was fought at Gondar on November 27 (Pankhurst 245-249).
Mockler, Anthony. Haile Selassie's war. New York: Olive Branch Press, 2003.