The British force consisted of 45 Commando (45 CDO), Royal Marines under Lieutenant-Colonel Andrew Whitehead (who later became a general) with support from six 105 mm guns of 29 Commando Regiment, Royal Artillery. 2 PARA was in reserve. Naval gunfire-support was provided by HMS Glamorgan's 2 x 4.5 inch (114 mm) guns. The Argentinian force consisted of the 4th Infantry Regiment (RI 4). Command of Two Sisters was entrusted to Major Ricardo Cordón, second in command of RI 4, with the bulk of the defenders drawn from C Company with the 1st Platoon (Sub-Lieutenant Miguel Mosquera) and 2nd Platoon (Sub-Lieutenant Jorge Pérez Grandi) on the northern peak and the 3rd Platoon (Sub-Lieutenant Marcelo Llambias) on the southern peak and the 1st Platoon A Company (Sub-Lieutenant Juan Nazer) and Support Platoon (Second Lieutenant Luis Carlos Martella) on the saddle between the two peaks. Major Óscar Jaimet's B Company of the 6th Regiment (RI 6) acting as the local reserve occupied the saddle between Two Sisters and Mount Longdon.
On 4 June the three companies of 45 CDO advanced on Bluff Cove Peak, on the lower slopes of Mount Kent, and were able to occupy the feature without opposition and was met by patrols from the SAS. Enemy opposition was desultory but on the night of 29 May a fierce firefight developed in taking the two important hills, that were intended to form part of an Argentine Special Forces line. Captain Andrés Ferrero's patrol (3rd Assault Section, 602 Commando Company) made the base of Mount Kent but were then promptly pinned by machinegun and mortar fire. One Argentine NCO was wounded. Air Troop had two wounded from rifle fire. Probing attacks around the D Squadron positions continued throughout the night and at 11:00 am on 30 May, about 12 Argentine Commandos tried to get up the summit of Bluff Cove Peak, but were driven off by D Squadron SAS which killed two of the party, First Lieutenant Rubén Eduardo Márquez and Sergeant Óscar Humberto Blas. First Lieutenant Márquez and Sergeant Blas showed great personal courage and leadership in the contact and were subsequently awarded the Argentine Nation to the Valour in Combat Medal. During this contact the SAS suffered two casualties from grenades. The Argentine Commandos literally stumbled on a camp occupied by 15 SAS troopers, according to special forces historian Martin Arostegui who wrote Twilight Warriors: Inside The World's Special Forces (p. 205, Bloomsbury, 1995). Throughout 30 May Royal Air Force Harriers were active over Mount Kent. One of them in responding to a call for help from D Squadron attacked Mount Kent's eastern lower slopes and that led to its loss through small-arms fire.
A heavy mist hung over the Murrell River area and this assisted the 45 Commando Recce Troop to reach and sometimes penetrate the Argentine 3rd Platoon position under Sub-Lieutenant Marcelo Llambias. Marine Andrew Tubb of Recce Troop was on these patrols:
We were actually inside the Argentine position, so we ended up shelling ourselves. We did a lot of patrols up to Two Sisters ... that time [6 June] we pepper-potted [retreated] for about 400 metres to get out [the 3rd Platoon sergeant, Ramón Valdez, had launched a counterambush], through the Argy lines firing 66 [mm] rockets to fight through and regroup. We got artillery again to smoke us out. It took us well over an hour to get away and it seemed like a few minutes. We killed seventeen of them [two Army privates and three Sappers of a Marine mine-laying party were actually killed], and all we had was one bloke with a flesh wound.|20px|20px|Robin Neillands|By Sea & Land: The Story of the Royal Marine Commandos, p. 402, Cassell Military Paperbacks, 2000
For his patrol action, Lieutenant Chris Fox received the Military Cross. In general terms, the Argentines were thoroughly entrenched, about 6000 metres or less across a no-man's-land. The Argentine positions were mined and patrolled heavily.
At about 2.10 am local time on 10 June a strong 45 Commando fighting patrol probed the 3rd Platoon position. In the ensuing fight Special Forces Sergeants M. Cisneros and R. Acosta were killed; two more Argentine Special Forces lying in ambush for the Royal Marines were wounded. The British military historian Bruce Quarrie wrote later:
A constant series of patrols was undertaken at night to scout out and harass the enemy. Typical was the patrol sent out in the early hours of the morning of 10 June. Lieutenant David Stewart of X-Ray Company, 45 Commando, had briefed his men during the previous afternoon, and by midnight they were ready. Heavily armed, with two machine-guns per section plus 66 mm rocket launchers and 2-inch [described by the British as 81 mm] mortars, the Troop moved off stealthily into the moonlit night towards a ridge some 4 km away where Argentine movement had been observed. Keeping well spaced out because of the good visibility, they moved across the rocky ground using the numerous shell holes for cover, and by 04.00 [1 am local time] were set to cross the final stretch of open ground in front of the enemy positions. Using a shallow stream for cover, they moved up the slope and deployed into position among the rocks in front of the Argentine trenches. With the help of a light-intensifying night scope, they could see sentries moving about. Suddenly, an Argentine machine-gun opened fire and the Marines launched a couple of flares from their [81 mm] 2-inch mortars, firing back with their own machine-guns and rifles. Within seconds three Argentine soldiers and two Marines were dead. Other figures could be seen running on the hill to the left, and four more Argentine soldiers fell to the accuracy of the Marines' fire. By this time, the Argentine troops further up the slope were wide awake, and a hail of fire forced the Marines to crouch in the shelter of the rocks. The situation was becoming decidedly unhealthy and Lieutenant Stewart decided to retire, with the objective of killing and harassing the enemy well and truly accomplished. However, a machine-gun to the Marines' right was pouring fire over their getaway route, and Stewart sent his veteran Sergeant, Jolly, with a couple of other men to take it out [They knew they were cut off with what looked a poor chance of escape. In these circumstances any panic or break in morale and the game was up]. After a difficult approach with little cover, there was a short burst of fire and the Argentine machine-gun fell silent. Leapfrogging by sections, the Troop retreated to the stream, by which time the Argentine fire was falling short and there were no further casualties.|20px|20px|Bruce Quarrie|The Worlds Elite Forces, pp.53-54, Octopus Books Limited, 1985
Major Aldo Rico, commander of the 602 Commando Company himself had a lucky escape when an enemy rocket exploded uncomfortably close. Sadly for 45, on the night of 9-10 June there was an unfortunate mistake made in the dark and friendly fire was exchanged resulting in British casualties.
Captain Ian Gardiner's X-Ray Company spearheaded the attack on Two Sisters, accompanied by the Unit's Commando trained padre, the Revd Wynne Jones. Lieutenant James Kelly's 1 Troop took the western third of the spineback on the southern peak of Two Sisters (Long Toenail) with no fighting taking place. However at 11:30 pm local time (see No Picnic, p.131), Lieutenant David Stewart's 3 Troop ran up against a very determined defence on the spineback and were unable to get forward. Beaten from their attempt to dislodge the Argentine 3rd Platoon, Lieutenant Chris Caroe's 2 Troop threw themselves at the platoon but the attack was dispersed with the help of artillery fire. For three or four hours X Ray Company was pinned down on the slopes of the mountain. (Source ) Naval gunfire ripped back and forth across the mountain, but the Argentines held the Royal Marines off. Colonel Andrew Whitehead realized that a single company could not hope to secure Two Sisters without massive casualties, and brought up the battalion's two other companies.
At about 12:30 am local time (see No Picnic, p. 132) Yankee and Zulu Companies attacked the northern peak (Summer Days) and after a very hard two hour fight against two platoons and despite heavy machinegun and mortar fire, succeeded in capturing 'Summer Days'. The Z Company platoon commander, Lieutenant Clive Dytor, won the Military Cross by rallying his 8 Troop and leading it forward at bayonet point to take Summer Days. Yankee Company then advanced to attack the final objective capturing all of its objective all the way to the eastern end of Two Sisters. Second Lieutenant Aldo Eugenio Franco and his RI 6 platoon successfully prevented Yankee Company from attacking C Company as it withdrew from Two Sisters. Private Oscar Ismael Poltronieri who held up Yankee Company with accurate shooting with his rifle and a machinegun, was awarded the Argentine Nation to the Heroic Valour in Combat Cross (CHVC), the highest Argentine decoration for bravery. (Source Martin Middlebrook, The Fight For The Malvinas, Leo Cooper Paperbacks, 2003)
The next morning Colonel Andrew Whitehead looked in wonderment at the strength of the positions the enemy had abandoned. 'With fifty Royals,' he said, "I could have died of old age holding this place.' (Max Hastings, Going To The Wars, p. 363, Macmillan 2000) Although the British battalion seemed at the time to have had an easy victory, those actually engaged with the enemy platoons would have been unlikely to agree.
The British senior officers were highly critical of the 6th Infantry Regiment's 'B' Company who, they claimed, withdrew in a disorderly manner from front-line positions at the opening of the battle, although this seems to have little foundation. Indeed, the company withdrew in good order. The Argentine Army Official Report on the war recommended Major Oscar Jaimet and CSM Jorge Pitrella of the 6th Regiment's B Company for an MVC (Argentine Nation to the Valour in Combat Medal) for their conduct of their fighting withdrawal and subsequent behaviour on Tumbledown (this was later granted to Major Jaimet, Pitrella was awarded the Argentine Army to Military Merit Medal). (See for details.) Sergeant-Major George Meachin of Yankee Company, would later praise the fighting abilities and spirit of the Argentine defenders:
We came under lots of effective fire from 0.50 calibre machine guns ...At the same time, mortars were coming down all over us, but the main threat was from those machinegunners who could see us in the open because of the moonlight. There were three machineguns and we brought down constant and effective salvoes of our own artillery fire on to them directly, 15 rounds at a time. There would be a pause, and they'd come back at us again. So we had to do it a second time, all over their positions. There'd be a pause, then 'boom, boom, boom,' they'd come back at us again. Conscripts don't do this, babies don't do this, men who are badly led and of low morale don't do this. They were good steadfast troops. I rate them.|20px|20px|Bruce Quarrie|op. cit., p. 55, Octopus Books Limited, 1985
Hugh Bicheno described the moonscape of devastation:
Although Wireless Ridge and the saddle between Tumbledown and William are still heavily scarred, even after more than twenty years the beaten zone between the Two Sisters bear the most eloquent witness to the awesome power of the British artillery, which fired 1,500 shells at the Two Sisters that night. The still-churned area occupied by Nazer's platoon in particular leaves one in no doubt why they decamped immediately, while the saddle itself is dimpled with craters, testimony to the tenacity of Martella's HMGs and mortars. (Hugh Bicheno, .|20px|20px|Hugh Bicheno| Razor's Edge: The Unofficial History of the Falklands War, p. 242, Weidenfeld & Nicolson, 2006
With the telephone lines to the command post in shreds, Llambias-Pravaz led his men to join M Company 5th Marine Infantry Battalion on Sapper Hill.
The X-Ray Company Marines were in awe of the depleted 3rd Platoon who had put up such determined resistance, and their company commander in the book Above All, Courage (Cassell Military Paperbacks, 2002) later said:
A hard cadre of some twenty men had stayed behind and fought, and they were brave men. Those who stayed and fought had something. I for one would not wish to face my Marines in battle.
A lone rifleman on Long Toenail held out long after resistance had ended on the mountain. There was a humorous moment when the Revd Wynne Jones called to his Marines that he was 45 Commandos' padre.
Losses to the Commando had been high. Three Royal Marine Commandos and one Marine from 59 Independent Commando Squadron, Royal Engineers were killed taking Two Sisters and a further four had died in the skirmishes in no-man's-land, bringing the total to eight killed. Another 17, including platoon commanders (Lieutenants Fox, Dunning and Davies) had been wounded. Some 20 Argentines died in the first eleven days of June and the night of battle. Another 54 Argentines were taken prisoner. HMS Glamorgan stayed in her position offshore to support the Royal Marine Commandos who were pinned down and there is no doubt the light cruiser saved many British lives. Glamorgan stayed when she was past the time she was meant to leave and was hit by a land based Exocet missile, thirteen sailors were killed as a result of this attack.
For the bravery shown in the attack on Two Sisters, men from 45 Commando were awarded one DSO, three Military Crosses, one DCM and four Military Medals. A commando from 29 Commando received a Military Medal as did a man from the M&AW Cadre.