The Argentine defenders consisted of ex-Army Green Beret Captain Carlos Alberto Arroyo's B Company from Lieutenant Colonel Diego Alejandro Soria's 4th Monte Caseros Infantry Regiment (RI 4).

On 1 June, the Argentine defenders on Harriet and Two Sisters, after having abandoned their field kitchens in their original positions on Mount Challenger, were given permission by their officers to consume their cold-weather ration packs, which helped raise the morale of the conscripts.

[3] On the night of 30 May, elements of K Company, led by Captain Peter Babbington of 42 CDO boarded three Sea King helicopters and moved forward of San Carlos to secure Mount Kent at 1,093 ft (333 m),[4] one of the tallest of the peaks surrounding Stanley where Major Cedric Delves' D Squadron from the Special Air Service (SAS) had established a presence.

By the end of May, D Squadron had secured Mount Kent at the cost of two wounded in Air Troop (Dick Palmer and Carl Rhodes[5]) from small-arms fire[6] with another SAS man having broken his hand taking cover during the engagement,[7] and Boat Troop with Tactical HQ started patrolling Bluff Cove Peak, which they took with the loss of another two SAS wounded (Ewen Pearcy and Don Masters) hit by hand grenade splinters or rock fragments,[8][9][10][11] including a Spanish-speaking Warrant officer attached from 23 Special Air Service Regiment (Reserve) who had joined Delves to interrogate any captured Argentines.

At the same time, Captain Matthew Selfridge's D Company scouting ahead of 3 PARA took Teal Inlet Settlement, at the cost of one wounded through an accidental discharge.

[16] However, at around 11.00 hours (local time) the Recce Troop opened fire and two conscripts (Privates Celso Paez and Roberto Ledesma) were instantly killed, and their NCO (Odorcic) went down, concussed when shot in the helmet by one of the Marine snipers.

[15][17] The Primary Forward Air Controller, commando-trained Flight Lieutenant Dennis Marshal-Hasdell, remembers: We were separated from our heavy bergens with the radios and all our gear.

[18] The Ferranti laser-target-designator retrieved in the contact showed that the Royal Marines were seeking to destroy the Argentine bunkers on Mount Harriet with 1,000-pound GBU-16 Paveway II dropped by RAF Harriers.

[19] However, on the night of 5–6 June, Captain Andrés Ferrero's 3rd Assault Section from 602 Commando Company attacked Lieutenant Hornby's men on Mount Wall and the Royal Marines were forced to withdraw.

XX377 of 656 Squadron) that was bringing forward communications equipment for the planed advance of the 5th Infantry Brigade in the form of the supporting 42 CDO through Harriet and Williams was shot down in a friendly fire incident by a Sea Dart missile launched by HMS Cardiff, all four men in the helicopter were killed.

Sub-Lieutenant Pasolli's men attacked and the Scots Guards returned fire with two Bren machine guns but were forced to abandon their rucksacks and radios.

The battle for Mount Harriet began on the evening of 11 June with a heavy naval softening-up bombardment that killed two Argentinians and wounded twenty-five.

[37][38] John Witheroe, one of the British war correspondents, later recalled the heavy Royal Navy bombardment: We were involved with one night attack on Mount Harriet when the Welsh Guards were coming up as a back-up.

During the engagement, Second Lieutenant Juárez was badly wounded firing his handgun in the dark and Corporal Laurence G Watts from K Company was killed clearing the occupants of a tent.

[44] The supporting British artillery batteries and mortar crews fired over 1,000 rounds to keep the Argentines pinned down, and helped stop the defenders getting a proper aim at the Royal Marines from K and L Companies.

Each time a Royal Marine moved, Corporal Roberto Bacilio Baruzzo would open fire with the help of his night vision rifle scope, to make it appear there was only one enemy sniper holding up K Company.

[48][49] With half a platoon of RI4 and RI12 riflemen and a 7.62 mm general-purpose machine gun team threatening to blunt the British advance, Newland darted out from cover and charged the enemy.

He neutralized the machine gun with grenades and killed three Argentine soldiers,[50] but on reaching the rear of the position, Corporal Baruzzo shot Newland in both legs.

L Company requested mortar fire onto the Argentines; a mixture of High explosive (HE) and White phosphorus (WP); then 5 Troop moved forward supported by the 15 machine-guns positioned on the ridge.

[70] They took 3 prisoners although most of Jiménez-Corbalán men had withdrawn after losing two killed in the night fighting (Privates Juan José Acuña and Carlos Epifanio Casco).

The platoon of Oscar Augusto Silva continued to resist from Goat Ridge in the early morning light and a determined conscript (Orlando Aylan), in a position just below the summit of Mount Harriet held up L Company with accurate shooting until killed by an 84mm anti-tank rocket fired at short range.

[74] At some time in the early morning darkness, Second Lieutenant Jiménez-Corbalán's 3rd platoon were making their way to new positions on Mount William, the officer was concussed and temporarily blinded when he set off an Argentine booby-trap while leading his men through a minefield.

[79] On 13 June, a Welsh Guards messenger (Lance Corporal Chris Thomas), bringing forward food supplies to Major Christopher Drewrywe's Number 2 Company (1WG), via Mount Harriet's lower slopes was killed when his motorbike ran over a mine or was hit by mortar fire.

The night battle had lasted longer than expected, leaving no time for 42 Commando to capture Mount William under the cover of darkness as had been planned.

Some British reporters were thus misled into depicting the Argentineans as hapless teenage conscripts who caved in after the first shots were fired, but Royal Marine Warrant Officer 2 John Cartledge, who served with L Company during the battle, corrected them, saying the Argentines were good soldiers who had fought properly:They used the tactics which they had been taught along the way very well, they were quite prepared for an attack.

Their small individual Lineman entrenching tools were all broken by the time they took over their new defensive-line after having constructed solid positions on Mount Challenger and Wall Mountain during May, as the Argentinian Regimental Commander explained to British military historian Martin Middlebrook.

[86] After the battle, Corporal Krishnakumar Rai[87]of the Queens Gurkha Engineers would be killed whilst engaged in clearing the minefield and booby-traps that the Argentine Marines had laid in nearby Goat Ridge, the same explosives that had injured Sub-Lieutenant Jiménez-Corbalán as he made his way to William with his men from Harriet.