4th Infantry Regiment (Argentinian Army)
The 4th Monte Caseros Infantry Regiment was raised in 18 August 1824, with the nucleus of the regiment coming together at Miramar, near Buenos Aires, on 18 July 1825.
In early April 1982 the 4th Regiment moved to Paraná, where it boarded transport planes to Comodoro Rivadavia. The regiment arrived at Port Stanley at the end of the month. Disembarking at BAM Malvinas (Malvinas Military Airbase) in the Fresinet Peninsula, the regiment traveled by foot to Murrell River. Mount Kent was being used as a base for the 601st Combat Aviation Battalion where the conscripts would complete their training. The 4th Regiment went into camp on Mount Challenger, south of Mount Kent.
Mount Harriet and Two Sisters Mountain
This situation had quickly changed in May. The British 3rd Commando Brigade had landed at San Carlos, pushing the Argentinian forces from Goose Green and Fitzroy. The 4th Regiment withdrew to Mount Harriet and Two Sisters and, with the 6th Regiment's Bravo Company, defended Stanley Common for the next fortnight.
The 4th Regiment participated in the usual pattern of defensive battles, manning parts of the Outer-Defence-Zone, working on the Monte Caseros Line, and aggressively patrolling No-Man's-Land. The Monte Caseros Line was Port Stanley's outer ring of defences and was a series of machine gun sangars forming a stronghold around the town.
The Battle of Two Sisters Mountain was one of three battles (the other two being the Battles of Mount Harriet and Mount Longdon) fought on the night of June 11th to June 12th, 1982.
British forces in the Battles of Mount Harriet and Two Sisters Mountain consisted of 42 Commando (42 CDO) and 45 Commando (45 CDO) Royal Marines under the commands of Lieutenant-Colonels Nick Vaux and Andrew Whitehead, supported by six 105mm guns of 29 Commando Regiment, Royal Artillery. Additionally, naval gunfire support was provided by the Royal Navy.
Resisting the British advance, were around 600 conscripts and regulars of the 4th, 6th and 12th Infantry Regiments under the command of Lieutenant-Colonel Diego Alejandro Soria and Majors Ricardo Cordón and Oscar Ramón Jaimet.
British casualties consisted of 10 killed and 50 wounded. The Argentinians suffered 40 killed, 100 wounded and about 300 Argentinians were taken prisoner.
In June and July the majority of Argentinians were evacuated by sea. The 4th Regiment was evacuated on 23 June and sailed to Puerto Madryn, from where it was transferred to the NCO School camp at El Palomar in Buenos Aires. The brigade later moved back to Paraná and then Monte Caseros for rest, training, and garrison duties.