As part of the East African Campaign (World War II) one of the objectives was to remove the Italians out of Ethiopia, which the Italians had invaded and occupied on 1936. The British decided that they would help Ethiopians forces that had deserted into Kenya and Sudan. They also decided that they would help those inside Ethiopia fighting the Italians and turn the population against the Italians. To guarantee the success of their attempts on Ethiopia, they decided to fly the emperor out of England, where he was in exile, into Khartoum.
In June 1940, Italy declared war on England. At the beginning of the war the Italians had the upper hand. They were better trained and they had more troops. During the first two months, the Italians and the British mostly held their positions, clashing intermittently in insignificant skirmishes. The Italians had minor successes on the Sudanese-Ethiopian border, encroaching on British territory. The first major attack was made by the Italians on British Somaliland in August. After two weeks of fighting the British retreated and the Italians took British Somaliland (Mockler 241-8) However, the Italians could have done more damage. The Italians overestimated the British position in Sudan and could have taken Khartoum (Mockler 235). Kenya was undermanned for the first two months of fighting (Mockler 239)
The hesitation by the Italians helped the British regroup and build up their army. Within Ethiopia, the British focused on Gojjam to help rebel forces and dropped leaflets announcing the return of the Emperor. When the Italians discovered the British effort in Gojjam, they countered it by restoring to power the old ruler of Gojjam, Ras Hailu, who had been imprisoned by the emperor before war broke out (Mockler 297)
For the first 7 month of the campaign, the emperor patiently waited for the British to unleash their attack. There was another matter weighing on the mind of the emperor: not everyone wanted to see Haile Selassie restored to the throne. Initially the British in the colonies were not happy with his presence. Some Ethiopians wanted the emperor not to rely on the British on the fear that after liberating Ethiopia they would become its new ruler. Later on there was some opposition from within the British army who favored Oromo government restoration instead of Amhara (Mockler 310) However the emperor was able to overcome each of these obstacles and was finally able to convince the British to put forth a major attack from Sudan. (Mockler 312)
The British offensive began in January 1941. Within weeks, the British retook territory they had lost to the Italians at the beginning of the war (Mockler 326). The emperor accompanied the attack from Sudan, led by Orde Wingate and his Gideon Force. By April they were able to take Gojjam. Ras Hailu chose not to fight and surrendered (Mockler 358). Another attack was made on Eritrea and that group took Asmara in March (Mockler 337). The attack from Kenya first took Mogadishu, followed by Harar and was the first to reach Addis Ababa in April (Mockler 370). Haile Selassie reached Addis Ababa on may 5, exactly five years after the Italians took the capital city.
Although the emperor had been restored to his throne, the British were the one's who had real control. The British took place of the Italians by take controlling of administration of the country, including taxation, etc... It was not until world war ii had ended and with help of Americans the emperor was able to rid of the new occupants and truly liberate Ethiopia.
Mockler, Anthony. Haile Selassie's war. New York: Olive Branch Press, 2003.