The British went into Eritrea knowing nearly everything the Italians had planned. By November 1940, the Government Code and Cypher School at Bletchley Park and the Cipher Bureau Middle East in Cairo had broken the replacement ciphers for the Regia Aeronautica and Regio Esercito. Italian wireless security was sloppy - Italian commanders used the air almost as freely as a telephone, and the frequencies were easy to monitor. Daily reports from Amedeo, the Duke of Aosta, viceroy of Italian East Africa, landed in British intelligence files sometimes before they reached their intended recipients. Operational plans for the Italian air force were read by British command before the squadrons flew. When the 4th and 5th Indian Divisions moved into Eritrea on 19 January 1941, they moved with a map of the opposing order of battle that was substantially up to date.

Agordat is a small town on the north bank of the Baraka River, a watercourse that is dry most of the year and edged with palm groves where it runs past the town. The Italians chose it as a defensive position because the terrain did most of the work for them. Two roads from Kassala converged here before continuing northeast to Keren and Asmara - the only route into the Eritrean highlands. To the southwest of the town rose the Laquetat ridge, with a concrete wall, wire entanglements, and forts at each end. To the southeast, four rocky outcrops - later nicknamed Tinker, Tailor, Soldier, and Sailor by the British soldiers who attacked them - had been fortified. Beyond those rose Mount Cochen, a peak several hundred meters above the plain. The Baraka itself barred the northern flank. Anyone attacking from the southwest had to fight uphill through a funnel of fire.

The 4th Indian Division moved against Agordat from 26 January. Initial attacks by the 4th Sikh Regiment and the 3/1st Punjab on Laquetat ridge were repulsed. The 3/14th Punjab climbed Mount Cochen in the dark on the night of 28 January. On 29 January the Italians reinforced Cochen with two fresh battalions, and the fighting on the ridge became hand-to-hand. Indian supply parties ran ammunition up the slopes by hand, not having enough mules for pack animals, and on more than one occasion the carriers dropped their loads to fix bayonets and plug gaps in the line. Bengal Sappers and Miners worked under fire. Italian pack artillery, manhandled behind the ridge, caught the attackers in enfilade and drove them back. By 30 January the 2nd Cameron Highlanders had taken a spur nicknamed Gibraltar and held it through repeated Italian counter-attacks.

The decisive morning was 31 January. Four Matilda I infantry tanks from the 7th Royal Tank Regiment had arrived at the front. The Italian M11/39 tanks and Fiat L3 tankettes defending Agordat were obsolete - some of the L3s were crewed by German volunteer sailors stranded in Massawa, now serving in borrowed Italian armor. The Matilda's thick frontal armor shrugged off the Italian main guns at the ranges offered. The 1st Battalion, Royal Fusiliers, attacking behind the four tanks, broke through Laquetat and the pass between Laquetat and Mount Cochen in minutes. The tanks destroyed eleven Italian armored vehicles and overran the artillery. The 3/1st Punjab passed through and took Tinker and Tailor by nightfall. The Italian commander, fearing encirclement, ordered a retreat to Keren - disorderly enough that 1,000 prisoners were left behind, along with 43 guns and 14 damaged tanks. Another 1,000 prisoners were taken during the pursuit.

The casualty figures for the Italian-led side are worth sitting with. The Italian forces and the Eritrean and Ethiopian askari who fought beside them lost, across Agordat, Barentu, and the retreat to Keren, 179 officers, 130 NCOs, 1,230 Italian other ranks, and 14,686 askari - a total of 15,916 men killed, wounded, or captured. The askari - Eritrean and Ethiopian soldiers fighting for Italian pay - suffered by far the heaviest proportion of the losses. They had been recruited, trained, and in many cases conscripted into a colonial army, and at Agordat they held the ground while the Italian officers directed. Amedeo Guillet's suicidal rear-guard action on 21 January had cost the Amhara cavalry roughly 800 killed or wounded - East African horsemen dying in the dust to buy time for a colonial empire that was already losing. Barentu fell on the night of 1-2 February. Wavell ordered Platt to press on to Keren and Asmara. The hardest fighting of the campaign still lay ahead, in the mountain passes above.