'Atmosphere' was the British establishment of a base at Mersa Kuba, to the north of Massawa, in order to facilitate the capture of the latter, which was the major port of Italian Eritrea, as the culmination of 'Excursion' (8 April 1941).

Under the leadership of Lieutenant General W. Platt, commander of the British forces in Sudan, during December 1940 and the first part of January 1941 the limited strength available round Eritrea made it impossible to undertake anything but limited attacks and a number of small excursions to harry the Italian forces. Thus the British offensive to take Eritrea could begin only after reinforcements had arrived in Sudan from Egypt. The arrival of an Australian infantry division in Egypt allowed General Sir Archibald Wavell, commanding the British forces in the Middle East, to release Major General N. M. de la P. Beresford-Peirse’s Indian 4^th Division from his 'Compass' plan in the Western Desert.

The main British attack on Eritrea was scheduled to start on January 18 against Kassala, but aggressive skirmishing in the previous month had prompted the Italians to withdraw on 17 January to the jagged foothills of the Eritrean plateau on the approaches to Agordat. On 19 January the Indian 4^th Division and Major General L. M. Heath’s Indian 5^th Division advanced into Eritrea in the direction of Agoirdat, which was strongly fortified. The Indian 4^th Division moved forward along the northern road via Keru, and the Indian 5^th Division along the southern road via Barentu. Within nine days, Platt’s forces had advanced 100 miles (160 km) and broken through the Italian positions in the foothills to capture Agordat.

The key action in the campaign then took place at Keren, 60 miles (97 km) farther to the east of Agordat on the way to the coast of the Red Sea, between 5 February and 1 April. At the beginning of the battle, the Italian forces available to Generale di Corpo d’Armata Nicolangelo Carnimeo, commander of the 2a Divisione coloniale, were the 11o Reggimento granatieri (including the Battaglione bersaglieri 'Africa'), 11a Brigata coloniale, 3o and 15o Battaglioni di cavalleria coloniale, 104o and 106o Battaglioni d’artigleria, and 2o and 5o Battaglioni d’artiglieria coloniale. Between 7 and 13 February this initial strength was reinforced by the Battaglione alpini 'Uork Amba', 2a, 5a and 44a Brigate coloniali, 2o Battaglione di cavalleria coloniale, 1/60o Reggimento d’artiglieria, 36o and 102o Battaglioni d’artiglieria, one anti-tank battery, and 6o, 11o and 12o Battaglioni d’artiglieria coloniale. Between 14 February and 14 March, there arrived the 11o Legione 'Camicie Nere', 44o Battaglione 'Camicie Nere', one machine gun battalion, 6a and 12a Brigate coloniali, 4o and 103o Battaglioni d’artiglieria, and 22o Battaglione d’artiglieria anti-aerea. Finally, between 15^th and 27 March there appeared the 150o and 170o Battaglioni 'Camicie Nere', and the 16a, 41a and 61a Brigate coloniali.

Early on 1 February 'Gazelle' Force, Colonel F. W. Messervy’s reconnaissance and advance force of the Indian 4^th Division, was checked as it tried to cross the Baraka river about 40 miles (65 km) from Keren at the point where the Ponte Mussolini had been demolished and the approaches to the river had been mined. By 12.00 on the following day, however, 'Gazelle' Force had crossed the river and moved up the Ascidera valley before being checked once again, this time in the Dongolaas gorge some 4 miles (6.5 km) from Keren: here the Italians had blocked the road by blowing the overhangs to fill the gorge.

Brigadier R. Savory’s Indian 11^th Brigade of the Indian 4^th Division moved up on 3 February, undertook a local reconnaissance on the following day, and on 5 February attacked to the left of the gorge. The 2/Queen’s Own Cameron Highlanders reached the top of the ridge in front of Sanchil, and during the night of 6 February, the 3/14^th Punjab Regiment passed through the Scottish battalion and advanced onto Brig’s Peak, where it was counterattacked by elements of the 65^th Divisione 'Granatieri di Savoia', which drove the Punjabis from their newly taken positions back toward Cameron Ridge, which was being reinforced by 1 (Wellesley’s)/6^th Rajputana Rifles.

The location of fighting over the following 10 days, the ridge was overlooked to its front by Sanchil, its left by Mt Sammana and even from behind by other mountains along the Ascidera valley. Here the Cameron Highlanders and Rajputana Rifles managed to retain their positions despite the fact that they were under almost constant attack and had to carry all the food, water and ammunition they needed some 1,500 ft (460 m) across exposed ground.

By 6 February Brigadier W. L. Lloyd’s Indian 5^th Brigade of the Indian 4^th Division had arrived, and on the following day advanced against the Dologorodoc feature to the east of the gorge, looping right through the Scescilembi valley (otherwise 'Happy Valley') before driving toward the north-west in the direction of the Acqua Col, which was the ridge connecting Mt Zelele and Mt Falestoh. During the night of 7 February one company of the 4 (Outram’s)/6^th Rajputana Rifles seized and held the col until 04.30, when it ran out of ammunition and had therefore to fall back on the rest of the battalion on a lower feature. Later on 8 February, after surviving most of the day under heavy artillery and mortar fire, the battalion had to pull back right to its start line.

The second phase of the Battle of Keren lasted from 10 to 13 February. During the afternoon of 10 February, the 3/1^st Punjab Regiment attacked Brig’s Peak, and by the morning of the next day had reached the top of Mt Sanchil. The major problem faced by the battalion was the need for men to move supplies of all types to the front line, and to carry back the casualties, and this meant that only two platoons available to hold the feature. After heavy heavy artillery and mortar fire throughout the day, and sustaining heavy losses, these platoons were forced off Mt Sanchil and Brig’s Peak by a strongly delivered counterattack by the Granatieri di Savoia, and the British-led force was now faced with the defence of Cameron Ridge under very dire circumstances.

Despite the fact that the Punjabis had not been able to hold Mt Sanchil, which provided excellent observation positions, another attack was launched against Acqua Col on 12 February. Brigadier J. C. O. Marriott’s Indian 29^th Brigade of Major General L. Heath’s Indian 5^th Division had been brought up from Barentu to come under command of the Indian 4^th Division, which held the brigade ready for the exploitation of the breakthrough that was expected. At 05.30, supported by an artillery barrage, the 4/6^th Rajputana Rifles once again spearheaded the advance to the crest of the col even as the 4/11^th Sikh Regiment was pushing round the side of Acqua Col, but the attack was unsuccessful for lack of adequate strength: this could have been provided by the 2/5^th Mahratta Light Infantry, but this battalion had been diverted to aid in the defence of Cameron Ridge.

The third phase of the Battle of Keren took place between 15 and 27 March after Platt had decided to pause, regroup and train before resuming the fight. To ease the logistic situation by limiting the number of front-line forces that had to be fed and otherwise maintained, and thereby make it possible for larger quantities of ammunition to be stockpiled in preparation for the renewed attack, the Indian 5^th Division was pulled back to Kessala, where it could be maintained by rail as it was retained and prepared before being returned to the front.

The 1^st Duke of York’s Own Skinner’s Horse and two of the three motor machine gun companies of 'Gazelle' Force were grouped in front of Arressa and Adi Ugri to threaten the Italian line of communication and reinforcement to Keren. Brigadier H. R. Briggs’s 'Briggs' Force (two battalions of Briggs’s own Indian 7^th Brigade of the Indian 4^th Division and the two Free French battalions of Colonel Monclar’s Brigade d’Orient) also arrived from the north. After entering Eritrea on the Red Sea coast, 'Briggs' Force had captured Karora and then driven south to take Kubkub before, on 1 March, breaking through the Mescelit pass about 15 miles (24 km) to the north-east of Keren. The arrival of 'Briggs' Force not only provided a third possible axis to attack the defenders of Keren, but also posed a threat to Massawa on the coast, thereby pinning Italian reserves in the port city and its environs.

Thus the situation was created for the climactic phase of the Battle of Keren with Beresford-Peirse’s Indian 4^th Division concentrated on the Mt Sanchil side of the gorge and Heath’s Indian 5^th Division on the 'Happy Valley' side: the British-led forces totalled something more than 13,000 men. By this time the defenders of Keren had also been reinforced, as noted above, to an overall strength of 25,000.

The British plan was that on the left Beresford-Pierce’s Indian 4^th Brigade would commit Savory’s Indian 11^th Brigade, with five battalions under command, against the peaks of the Mt Sanchil massif and Lloyd’s 5^th Brigade against Mt Sammana on the left of his front. On the right, Heath’s Indian 5^th Division was faced by the tactical situation created by the arrival and commitment of the Italian reinforcements on the Fort Dologorodoc area meant that 'Happy Valley' was dominated by the Italians and the British artillery had therefore had to be pulled back from its forward positions into the greater safety of the valley. It was now considered that without artillery support it was no longer practical to continue the flanking attack over the Acqua Col to threaten Fort Dologorodoc’s lines of communication.

Heath decided that Fort Dologorodoc was the primary objective of his Indian 5^th Division, for the capture of the fort would not only give the attackers the artillery observation post they needed to direct fire on both sides of the gorge, but also would make it possible for the reverse slopes of the Fort Dologorodoc mass, which up to now it had been impossible to target with artillery fire, and had therefore been used by the Italians to provide an artillery-free area for the gathering of men and supplies, to be taken under direct fire from the fort.

It was planned that the two parts of the offensive would be committed one after the other on 15 March so that the full weight of the British artillery could be used for the preliminary bombardment of each of the objective areas.

At 07.00 on 15 March, the Indian 4^th Division attacked from Cameron Ridge toward Mt Sanchil, Brig’s Peak, Hog’s Back and the three peaks of Mount Sammana. Continuing into the night, the fighting was severe as the battle ebbed and flowed, and the casualties on each side were very heavy.

Meanwhile, on the right, the Indian 5^th Division launched its attack on the Dologorodoc mass at 10.30 on 15 March. The 2/Highland Light Infantry of Brigadier W. J. Slim’s Indian 10^th Brigade, under the temporary command of Lieutenant Colonel B. Fletcher, led the attack on the lower features ('Pimple' and 'Pinnacle') but in daylight found progress impossible because of the Italian fire from the overlooking Mt Sanchil, where the defenders had beaten off the attack of Savory’s Indian 11^th Brigade. The men of Slim’s brigade were pinned, taking casualties and without supply, until the all of night provided the opportunity to pull back.

By the light of the moon on that same evening, the attack on the Dologorodoc mass was taken up by the Indian 9^th Brigade, whose command had been taken over from Brigadier M. Mayne by Messervy, newly promoted to brigadier. Heath and Messervy had planned an attack on 'Pimple' and 'Pinnacle' by almost two battalions, with a third battalion ready to pass through and assault Fort Dologorodoc.

The capture of 'Pinnacle' that night by the 3/5^th Mahratta Light Infantry, with the 3/12^th Frontier Force Regiment less two companies under command to take 'Pimple', had rightly been described as one of the outstanding small actions of World War II, decisive in its results and formidable in its achievement. During the early hours of 16 March, the Italian defenders of Fort Dologorodoc made a fierce counterattack, lasting for several hours, on 'Pinnacle' and 'Pimple'. Unfortunately for the Italians, this left Fort Dologorodoc partially denuded of defenders, and this allowed the 2/West Yorkshire Regiment to make its way over a seemingly impossible knife-edge to surprise the fort’s remaining defenders and defeat them is a savage fight ending in a British victory by 06.30. The Italians lost 400 men taken prisoner, and Platt at last had in his possession the artillery observation point his divisions so greatly needed.

The Italians delivered a series of counterattacks right through 16 March, and Marriott’s Indian 29^th Brigade made an unsuccessful attack during the evening on Falestoh and Zeban, which were abandoned after dark on 17 March after a day exposed to searing heat, fierce fighting and no resupply. For the next 10 days, the Indian 5^th Division’s position at Fort Dologorodoc, which was exposed to the Italians on three sides, was the site of fierce combat as the Italians committed newly arrived reinforcements in a vain attempt to retake this key position.

Meanwhile, on Mt Sanchil the Indian 4^th Division, with the Indian 10^th Brigade under command, maintained its steady but unavailing pressure. On the night of 17 March the elements of the hard-hit Indian 4^th Division withdrew from the slopes of Mt Sanchil and Brig’s Peak, and the Indian 10^th Brigade was returned to the Indian 5^th Division to re-form. Despite its reverses on Mt Sanchil and Brig’s Peak, the Indian 4^th Division continued to hold Hog’s Back and Flat Top. Over the next three days, the Italian forces made still more determined counterattacks on each side of the Dongolaas gorge, many of these involving savage close combat.

Platt and his subordinate commanders now came to the decision that their climactic attack should be made directly through the Dongolaas gorge rather than round its sides. Of the subordinate commanders Heath believed that the Italians, confident that its natural difficulties made it effectively impassable, might not have added man-made defences. On the nights of 16/17 and 17/18 March, therefore, small engineer parties reconnoitred the road block and started initial efforts to remove it, failing as a result of fire from the Italian lines. However, the information these parties brought back persuaded Heath that the key to the gorge was not Mt Sanchil but rather a pair of smaller features, the 'Railway Bumps', that overlooked the roadblock and could be approached with much less opposition along the railway line from the tunnel below the south-eastern end of Cameron Ridge.

So it was planned that an attack on the Italians at the head of the gorge would be made to provide the engineers (the Indian 5^th Division had four field company’s of Indian sappers and miners) with two days free of Italian mortar and machine gun fire in which to clear the road. For this Heath needed his full division, and this meant a pause as the Indian 10^th Brigade refitted after its savage treatment its had received on Mt Sanchil.

The plan was for the Indian 10^th Brigade to advance into the gorge while Messervy’s Indian 9^th Brigade, currently holding the Fort Dologorodoc positions, moved down to take three smaller hills overlooking the far end of the gorge and Marriott’s Indian 29^th Brigade then attacked to take Mt Zeban and, beyond this and to the east, Mt Canabai, which overlooked the town of Keren and guarded the road to Asmara. Command of the Indian 10^th Brigade was assumed on 21 March by one of Heath’s divisional staff officers, Brigadier T. W. 'Pete' Rees while his predecessor, Fletcher, created the mobile 'Fletcher' Force, comprising the Central India Horse (21^st King George V’s Own Horse) of the Indian 4^th Division and 12 Matilda II infantry tanks, to exploit the expected breakthrough in the gorge and move rapidly into the Italian rear area to attack the Italian reserves.

On 24 March there were diversionary attacks on Mt Sanchil, and just before 24.00 the 2/West Yorkshires and the 3/5^th Mahrattas in Fort Dologorodoc moved down to take the lower hills overlooking the gorge. The 2/West Yorkshires were able to take their hill unopposed, but the 3/5^th Mahrattas encountered strong opposition from dug-in positions. By 07.30 all three hills had been taken, however, and the gorge’s defences on its south-eastern side had been silenced.

At 03.00 on 25 March the 2/Highland Light Infantry and the 4/10^th Baluch Regiment on their right advanced from the railway tunnel, previously cleared by the sappers and miners, up the gorge. One hundred pieces of artillery were pouring their fire on the ridge above them on Mt Sanchil to suppress any defensive fire from this dominating height, and the attack up the gorge achieved total surprise as the Italians' attention was fixed on Mt Sanchil. The 3/2^nd Punjab Regiment then advanced between the 4/10^th Baluchis and 2/West Yorkshires to clear the gorge. By 05.30 the 'Railway Bumps' and most other objectives had been taken, and the Italians no longer held the positions from which to direct fire into the gorge.

The sappers and miners worked to clear the road even as the fighting continued on Mt Sanchil and Fort Dologorodoc, and by 12.00 on 26 March they had reopened the road through the gorge.

Early in the morning of 27 March, the British artillery turned its attention to Mt Zeban and Mt Falestoh. Marriott’s Indian 29^th Brigade passed through Messervy’s Indian 9^th Brigade to launch its attack at 04.30 only to discover that the defenders had withdrawn, and the men of the brigade were therefore able to occupy Falestoh Ridge and the two Zeban summits without opposition.

The Italian position was now untenable, and by first light the Royal Air Force was reporting their withdrawal along the road from Keren to Asmara. The defenders on the Mt Sanchil ridge were less fortunate and, now effectively cut off, the Granatieri di Savoia and Battaglione bersaglieri 'Africa' had to surrender. 'Fletcher' Force had reached Keren by 10.30, and then moved along the road toward Asmara in pursuit of the retreating Italians. The capture of Keren opened the land link between eastern Sudan and Asmara. British air units now started to attack the Italian columns retreating to the east in the direction of Asmara and also to the south in the direction of Gondar in northern Abyssinia.

The Italians had lost 12,147 men killed and some 21,700 wounded or taken prisoner, and the British-led forces lost 536 men killed and 3,229 wounded.

Platt now committed the Indian 5^th Division to the south-east in pursuit toward the Eritrean capital, some 50 miles (80 km) distant, and left the Indian 4^th Division to mop up in Keren and then return to Egypt. The road linking Keren and Asmara was well suited to the implementation of delaying tactics, and the Italians had for some time prepared to hold the advance of the British forces near Ad Teclesan (Adi Tekelezan), but this position was considerably less defendable that that at Keren, and on 31 March, after a one-day action, the Ad Teclesan position fell to Mayne’s Indian 9^th Brigade, yielding 460 prisoners and 67 guns. This had been the last practical defensive position to the west of Asmara, and the Italians fully appreciated that the loss of Ad Teclesan would in effect mean the loss of Eritrea. So on the following day the Italians surrendered Asmara, declaring it an open town.

After a three-day pause for resupply along the lengthening road to Kassala on the Sudanese border, the Indian 5^th Division set off west again toward Massawa, some 50 miles (80 km) away and 7,000 ft (2135 m) lower, on the coast of the Red Sea. The Italians had 10,000 troops and 100 tanks and armoured cars to defend Massawa, and another bloody battle seemed likely.

During the evening of 31 March three of the Italians' remaining six destroyers in the Red Sea had departed Massawa to attack British shipping and installations in and round the Gulf of Suez before scuttling themselves when they ran out of fuel and/or ammunition. Leone went aground shortly after leaving Massawa, and on the following morning she sank and the operation was cancelled. Aircraft had reported the stranded Leone and had seen another destroyer returning to Massawa, while the third reached port unseen. On 2 April all five remaining destroyers departed for Port Sudan, but their sailing was reported by aircraft from Aden. At dawn on the 3 April four of the destroyers were seen some 20 miles (32 km) to the east of Port Sudan by Fairey Swordfish reconnaissance and torpedo-bombing aircraft of Nos 813 and 824 Squadrons, which had flown from the fleet carrier Eagle at Alexandria to Port Sudan a few days before.

Reinforced by five Bristol Blenheim monoplane light bombers of the RAF’s No. 14 Squadron, these Swordfish biplanes sank Nazario Sauro and Daniele Manin. Pantera and Tigre were next to be located, close inshore in an area to the south of Jeddah on the Arabian side of the Red Sea, where they were being abandoned. Vickers Wellesley bombers of No. 223 Squadron from Port Sudan and the destroyer Kingston destroyed them. The only destroyer now thought still to be at large was Cesare Battisti, which had in fact developed a technical problem during the night and been scuttled.

The Italians had one success before their loss of Massawa, however, when the motor torpedo boat MAS-213 torpedoed the light anti-aircraft cruiser Capetown. After being towed to Port Sudan for interim repairs, the cruiser had to steam to Bombay for permanent repair.

As noted above, the Indian 4^th Division was already under orders to return to Egypt, leaving Briggs’s Indian 7^th Brigade under command of the Indian 5^th Division. On Platt’s orders, Heath sent light mobile forces south toward Adowa and Adigrat, and turned to his main task of capturing Massawa. His first action was to send an ultimatum to Ammiraglio di Divisione Mario Bonetti, commanding the Italian garrison of Massawa, by telephoning his headquarters on the undamaged line, and informed him that if the ships in Massawa were scuttled, the British would take no responsibility for feeding or evacuating the Italian population in Eritrea or Abyssinia. Bonetti answered that Maresciallo d’Italia Principe Amedeo Duca d’Aosta, the governor of Italian East Africa, had ordered him to maintain the Italian resistance, and therefore that no guarantee could be given regarding the ships.

The Indian 7^th Brigade soon reached the northern part of Massawa’s defences, and by 5 April the ring was closed by the arrival of Rees’s Indian 10^th Brigade (four battalions) and Colonel Raoul Magrin-Vernerey’s (otherwise Monclar’s) Free French Brigade d’Orient (two battalions). Bonetti was once more asked to surrender, but again refused. Early on 8 April an advance by the Indian 7^th Brigade met strong resistance, but a simultaneous attack by the Indian 10^th Brigade and B Squadron of the 4^th Royal Tank Regiment bit deeply into the western defences and the Free French troops broke into the south-western sector. Bombers of Nos 47 and 223 Squadrons co-operated throughout, principally by attacking the Italian artillery, which was notably active.

Early in the afternoon Bonetti surrendered his last 9,590 men and 127 guns. Much damage had been done to the harbour, all the ships had been scuttled, and large quantities of equipment and supplies had been dumped into the sea. Nevertheless a maritime supply line was quickly organised. By 27 April the railway between Massawa and Asmara had been reopened to traffic, and by 1 May the Indian 5^th Division’s main line of communication was running through Massawa. All organised opposition in Eritrea was now over.

The fate of all of the Italian warships had been established, and the handful of aircraft remaining in Ethiopia presented no danger.

The strategic object of the East African campaign, which was to remove the Italian threat to Allied convoys in the Red Sea and Gulf of Aden, had thus been achieved. On 11 April Heath had been promoted to command the Indian III Corps in Malaya, and command of the Indian 5^th Division passed to Mayne.