Agordat was an excellent defensive position and the British advance was slowed by delaying actions and mined roads but the attack began on 28 January on the left (northern) flank, which was repulsed.

Three columns of Italian and colonial forces comprising about 6,500 men launched the assault, supported by the Regia Aeronautica and some cavalry squadrons acting as vanguards.

[1] Kassala was defended by fewer than 500 men of the Sudan Defence Force (SDF, Major-General William Platt the al-qa'id al-'amm [Leader of the Army], known as the Kaid) and local police, who remained under cover during a twelve-hour bombardment by the Regia Aeronautica, then knocked out six Italian tanks and inflicted considerable casualties on the attackers.

Karora was occupied unopposed and on 7 July, another colonial battalion and banda supported by artillery and aircraft, attacked Kurmuk and overcame sixty Sudanese police after a short engagement.

[4] The Italian attacks had gained a valuable entry point to Sudan at Kassala and by capturing Gallabat made it harder for the British to support the indigenous Ethiopian resistance fighters, the Arbegnoch (Patriots), in Gojjam.

[6] Earlier in the month, Frusci had received orders from Rome to cancel plans to invade Sudan, withdraw from Kassala and Metemma in the lowlands along the Sudan–Eritrea border and hold the more easily defended mountain passes on the Kassala–Agordat and Metemma–Gondar roads.

[6] 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.

Sufficient low-grade ciphers had also been broken to reveal the Italian order of battle and the supply situation by the time that the British offensive began on 19 January 1941.

[10] While the garrison of Gallabat was ordered to reach Gondar, the 12th Colonial Brigade methodically retired towards the Keru–Biscia–Aicota triangle in the foothills of the Eritrean highlands, while opposing some resistance to Gazelle Force (Colonel Frank Messervy) a motorised unit from the SDF, the 4th and the 5th Indian Infantry divisions.

Guillet's deputy, Lieutenant Renato Togni, charged a column of Matilda tanks with his platoon of 30 colonial soldiers who were all killed but this allowed the remainder of the cavalry to disengage.

The charge cost the Amhara cavalry some 800 killed or wounded but slowed the British advance for long enough for the main Italian force to reach Agordat.

[14] The ground at Agordat was a natural defensive position and the defences mostly blocked an advance from the south-west from Biscia and Barentu; the northern flank was barred by the bed of the Baraka river.

[15] The 4th Indian Division was sent 40 mi (64 km) along the road to Sabderat and Wachai, thence as far towards Keru as supplies allowed, with the Matilda Infantry tanks of B Squadron, 4th RTR to join from Egypt.

A company from each of the Indian battalions had been detached because of insufficient mules and carried ammunition, water and food forward by hand, assisted by the Bengal Sappers and Miners.

[20] Several counter-attacks by the Askari and the Amhara Cavalry in the open failed and the 3/1st Punjab passed through the Fusiliers to attack four fortified hills, known as Tinker, Tailor, Soldier and Sailor.

The town was garrisoned by the 2nd Colonial Division (General Angelo Bergonzi) with nine infantry battalions (8,000 men) 36 tanks and armoured cars and 32 mountain guns in three defence lines.

On 31 January, the 1st Worcester captured rises to the west, despite stifling heat, thirst, moving through thorn bushes which tore clothing and slashed skin, over dry crumbly soil.

As news spread of the fall of Agordat, the garrison withdrew along tracks towards Adi Ugri and along the Asmara–Adua road on the night of 1/2 February, leaving behind about two battalions' worth of men to be taken prisoner, along with their guns and several medium and light tanks.

A message from the Duke of Aosta was found in which ordered Agordat and Barentu to be defended to the last man, because the terrain would nullify British superiority in tanks and wheeled vehicles.

[24] The defenders had retreated instead and the British realised that the rest of the Italian force in Eritrea was still well-equipped, when 300 rifles, thousands of rounds of ammunition and hand grenades were recovered.

[25] The Italian and colonial defenders of Agordat had fought a determined defence but Lorenzini had kept the 42nd Brigade south of the Baraka (Barka River) and neglected the opportunity to send it to counter-attack around the northern flank of the attackers.

The Italian retreats had been fairly well organised and though the British followed up as swiftly as possible, they lacked mobility; air support from the RAF was limited by the distance of their airfields from the front line.