[6] On 10 June 1940, Mussolini declared war on Britain and France, which made Italian military forces in Libya a threat to Egypt and those in the AOI a danger to the British and French colonies in East Africa.

Gaining control of Gojjam required the Italian garrisons to be isolated along the main road from Bahir Dar Giorgis south of Lake Tana, to Dangila, Debre Markos and Addis Ababa to prevent them concentrating against the Arbegnoch (Amharic for Patriots).

On 20 November, Wingate was flown to Sakhala to meet Sandford, and the RAF managed to bomb Dangila, drop propaganda leaflets and supply Mission 101, which raised Ethiopian morale, which had suffered much from Italian air power since the Second Italo-Abyssinian War.

[40] On 3 August 1940, the Italians invaded with two colonial brigades, four cavalry squadrons, 24 M11/39 medium tanks and L3/35 tankettes, several armoured cars, 21 howitzer batteries, pack artillery and air support.

Close to being cut off and with only one battalion left in reserve, Godwin-Austen contacted Henry Maitland Wilson, commander of the British Troops in Egypt in Cairo (Wavell was in London) and received permission to withdraw from the colony.

[48][49] The Italians also drove a platoon of No 3 Company, Eastern Arab Corps (EAC) of the SDF, from the small fort at Gallabat, just over the border from Metemma, about 200 mi (320 km) south of Kassala and took the villages of Qaysān, Kurmuk and Dumbode on the Blue Nile.

On 1 July, an Italian attack on the border town of Moyale, on the edge of the Ethiopian escarpment, where the tracks towards Wajir and Marsabit meet, was repulsed by a company of the 1st KAR and reinforcements were moved up.

The principal Italian naval force (Contrammiraglio [Rear-Admiral] Mario Bonetti) was based at Massawa in Eritrea, about 350 nmi (650 km; 400 mi) north of the Bab-el-Mandeb, well placed for the Red Sea Flotilla to attack Allied convoys.

On 18 November the cruiser HMS Dorsetshire bombarded Zante in Italian Somaliland[79] British naval forces supported land operations and blockaded the remnants the Red Sea Flotilla at Massawa.

By the end of 1940, the British had gained control of East African coastal routes and the Red Sea; Italian forces in the AOI declined as fuel, spare parts and supplies from Italy ran out.

[80] During 16 June 1940, Galileo Galilei sank the Norwegian tanker James Stove (8,215 gross register tons [GRT]), sailing independently about 12 nmi (22 km; 14 mi) south of Aden.

[84] The 31 ships of BN 7 were escorted by the cruiser Leander, the destroyer HMS Kimberley, the sloops Auckland, HMAS Yarra and HMIS Indus with the minesweepers Derby and Huntley, with air cover from Aden.

Clarke arranged for the Italian defences around Berbera to be softened up by air and sea raids from Aden and distributed maps and pamphlets on the climate, geography and population of British Somaliland.

[94] In November 1940, Gazelle Force operated from the Gash river delta against Italian advanced posts around Kassala on the Ethiopian plateau, where hill ranges from 2,000–3,000 ft (610–910 m) bound wide valleys and the rainfall makes the area malarial from July to October.

Wavell flew to Keren to assess the situation and on 15 March, watched with Platt as the Indians made a frontal attack up the road, ignoring the high ground on either side and breaking through.

On 11 April, the US President, Franklin D. Roosevelt, rescinded the status, under the Neutrality Acts, of the Red Sea as a combat zone, freeing US ships to use the route to carry supplies to the Middle East.

In response to the rapidly advancing British and Commonwealth forces and to the general uprising of Ethiopian Patriots, the Italians in Ethiopia retreated to the mountain fortresses of Gondar, Amba Alagi, Dessie and Gimma.

[110] On 6 April 1941, Addis Ababa was occupied by Harry Wetherall, Dan Pienaar and Charles Christopher Fowkes escorted by East African armoured cars, who received the surrender of the city.

[115] Both sides were short of food, ammunition, water and medical supplies; Wingate attempted a ruse by sending a message to Maraventano telling of reinforcements due to arrive and that the imminent withdrawal of British troops would leave the Italian column at the mercy of the Patriots.

[123] After the fall of Keren, Aosta retreated to Amba Alagi, an 11,186 ft (3,409 m) mountain that had been tunnelled for strong points, artillery positions and stores, inside a ring of similarly fortified peaks.

Although he realised that the approaching wet season would preclude a direct advance this way to Addis Ababa, he hoped that this action would cause the Ethiopians in the south of the country to rise up in rebellion against the Italians (the plot proved abortive).

The cruisers HMS Shropshire, Ceres and Colombo blockaded Kismayo and in the Red Sea, Pantera, Tigre and Leone based at Massawa in Eritrea made another fruitless sortie.

[130][m] Leatham formed Force T with the carrier HMS Hermes, the cruisers Shropshire, Hawkins, Capetown and Ceres, with the destroyer Kandahar to support Operation Canvas, the invasion of Italian Somaliland from Kenya.

[141] Five Blenheims of 14 Squadron RAF arrived in time to see Nazario Sauro hit and attacked a stationary destroyer and reported that its crew abandoned ship, that it was set on fire, exploded and sank but Cesare Battisti was later found beached on the Arabian coast.

[144][p] Vincenzo Orsini which had run aground at Massawa managed to refloat and was scuttled in the harbour on 8 April after being bombed by the Swordfish of 813 NAS; the torpedo boat Giovanni Acerbi was also sunk by aircraft.

[147] Operation Chronometer took place from 10 to 11 June, with a surprise landing at Assab by the 3/15th Punjab Regiment from Aden, carried by a flotilla comprising HMS Dido, Indus, Clive, Chakdina and SS Tuna.

At 7:00 a.m. the Civil Governor was taken to Dido and surrendered Assab to the Senior Officer Red Sea Force (Rear-Admiral Ronald Halifax) and the army commander, Brigadier Harry Dimoline.

[153] Uolchefit Pass was a position whose control was needed to launch the final attack on Gondar, was defended by a garrison of about 4,000 men (Colonel Mario Gonella) in localities distributed in depth for about 3 mi (4.8 km).

[159] In 2004, the American historian Douglas Porch wrote that the "pearl of the fascist regime" had lasted only five years, the performance of the Italian army exceeded that in North Africa but there had still been a high ratio of prisoners to casualties.

The British had withdrawn the 4th Indian Division and RAF squadrons for North Africa in February 1941, despite the Italian forces remaining at Amba Alagi, which from 20 April to 15 May, were steadily pressed back until they surrendered on 19 May.