Brigadier General William J. Slim's counterattack from Sudan on 6 November was beaten back, but Aosta was demoralized by a lack of supplies and Italian defeats in the Western Desert. He was also occupied suppressing Abyssinian rebels, known as the Patriots. At the moment of Britain's greatest weakness, he failed to take the initiative and unwisely adopted a defensive posture.
On 19 January 1941, Major General William Platt launched an offensive into Eritrea with the 4th and 5th Indian Divisions, aided by ultra intelligence from broken Italian army and air force codes. Platt captured Keren on 27 March after hard fighting, in what proved to be the decisive battle of the campaign. He entered Massawa on 8 April. There, the Italians scuttled one destroyer, and five others sortied into the Red Sea for an attack on Port Sudan. In the ensuing actions, the Italians had four of their destroyers sunk; the fifth was scuttled.
Meanwhile, on 11 February, Lieutenant General Alan Cunningham drove into Italian Somaliland from Kenya using the 11th and 12th African and 1st South African Divisions with startling success. After capturing Mogadishu, the capital of Italian Somaliland, on 25 February, he struck north and took Harar in Abyssinia on 26 March. A small force from Aden also captured Berbera on 16 March and quickly reoccupied British Somaliland with little opposition, to shorten the supply line, and then joined with Cunningham's force to capture Addis Ababa on 6 April. In just eight weeks, Cunningham's troops had advanced over 1,700 miles and defeated the majority of Aosta's troops, at a cost of 501 casualties.
Even more spectacular were the achievements of Lieutenant Colonel Orde Wingate, who commanded a group of 1,600 Patriots that he christened "Gideon Force." Through a combination of brilliant guerrilla tactics, great daring, and sheer bluff, he defeated the Italian army at Debra Markos on 6 April and returned Emperor Haile Selassie to his capital, Addis Ababa, on 5 May. British troops pressed Aosta's forces into a diminishing mountainous retreat at Amba Alagi until he finally surrendered on 16 May, ending Italian resistance in that theater, apart from two isolated pockets that were rounded up in November 1941.
The campaign in East Africa was important because, for the first time, a country occupied by the Axis had been liberated, another 230,000 Italian and colonial troops were captured, and British forces were released for vital operations in the Western Desert. It was also the first campaign in which ultra and the code-breakers at Bletchley Park played a decisive role, providing an invaluable lesson on the effective contribution that intelligence could make to the successful outcome of an operation. Success in East Africa also had an important strategic consequence, since U.S. President Franklin D. Roosevelt was able to declare, on 11 April, that the Red Sea and the Gulf of Aden were no longer war zones. U.S. ships were thus able to deliver supplies directly to Suez, relieving the burden on British shipping.
Paul H. Collier
Glover, Michael. Improvised War: The Abyssinian Campaign of 1940–1941. London: Leo Cooper, 1987.; Mockler, Anthony. Haile Selassie's War: The Italian-Ethiopian Campaign, 1935–1941. London: Grafton, 1987.