Today BIM-5, together with the 4th Marine Infantry Battalion (BIM-4), is based at Río Grande, Tierra del Fuego Province as part of the Argentine Navy's Fuerza de Infantería de Marina Austral (Southern Marine Corps Force, FAIA), formerly "Fuerza de Infantería de Marina N°1 (N°1 Marine Force, FIM1). They started the "Black Beret" tradition from a design made by Marine Sub-Lieutenant (naval rank equivalent to army captain) Abelardo "Tigre" (Tiger) Terré at the beginning of 1977, with then Marine Commander Manuel Tomé as its CO. After a gruelling Mountain and Cold Weather commando fighting course, they were dubbed the "Aguilas Australes" (Southern Eagles) and wore a black beret with a silver flash. Later on, the flash was changed to the unit's crest, and the use of the said beret spread throughout FIM1/FAIA. The Original "Aguilas Australes" flash is currently the semi-official logo of the Rio Grande Marine Garrison (Agrupación IM Río Grande).
Commanded by Marine Commander Carlos H. Robacio (now retired as a Marine Rear Admiral), BIM-5 was arguably the best Argentine infantry unit in the Falklands War. Although made up by conscripts, the unit's core of highly-professional NCOs and commissioned officers, along with a well developed training and logistics system, rendered BIM-5 a tough unit that fought well in the defense of Tumbledown Mountain. Different Argentine authorities have repeatedly decorated BIM-5's colors, while Marine Admiral Robacio is a holder of the French Légion d'Honneur and he was awarded the Argentine Nation to the Valour in Combat Medal.
Mount Tumbledown, Mount William and Sapper Hill lie west of Stanley. They were held by BIM-5, a reinforced, cold weather trained and equipped, marine battalion. During preparations for movement to the Falklands the Marine battalion was brought up to full strength of a light brigade with a company of the amphibious engineer company and a battery of the 1st Marine Artillery Regiment. The 5th Marines were further strengthened by three Tigercat SAM batteries of the 1st Marine Anti-Aircraft Regiment, and a heavy machine-gun company of Headquarters Battalion.
The BIM 5 positions around Port Stanley were bombarded, both from the sea by naval gunfire and from the air by the Royal Air Force Harriers. At 4.30 p.m., on 7 June, a British Harrier bombing positions held by the 5th Marine Battalion was hit by concentrated fire from M Company (under Marine Sub-Lieutenant Rodolfo Cionchi) on Sapper Hill.
12 June proved to be the toughest day for the Argentine Marines. From the moment the 2nd Battalion Scots Guards had finally been moved to Goat Ridge by helicopter, 1,500 rounds of artillery, descended upon the Marines, in preparation for the coming infantry assault.
On 13 June a diversionary action was fought to the northeast in order to raid the Cortley Ridge fuel dump. The 101st Anti-Aircraft Artillery Group's B Battery (B/GADA101) was assigned to defend the Fresinet Peninsula, a long, narrow piece of land running from Moody Brook to form the northern arm of Stanley, when their troops came under attack at 11 p.m. The incursion was carried out by the SAS and SBS in rigid raiders. They were engaged by the Marines with automatic weapons raked resulting in four wounded among the occupants. (Tony Geraghty, Who Dares Wins: The Special Air Service 1950 to the Gulf War, p. 156)
Further south, action was initiated shortly after 8 p.m., as the 2nd Scots Guards' Reconnaissance Platoon carried out a diversionary attack, advancing with four Blues and Royals Scorpion light tanks. As the British tanks came into range of the 5th Marine Battalion's O Coy (O/BIM5), one of the Scorpion tanks was incapacitated by a booby-trap. In a firefight that lasted two hours, three Marines were killed (Marine Conscripts Omar Iniguez, Omar Patrone and Juan Rava). The Guards decided to fall back towards the south but entered a minefield and were caught in a crossfire from the Mortar Platoon on Mount William and the Marines' artillery. BIM 5 coordinated fire support from Bravo Battery of the 1st Marine Field Artillery Battalion (B/BIAC and also guns of the Argentine Army's 3rd and 4th (Airborne) Artillery Groups (G.A.3/G.A.Aerot.4). The Guards sustained twelve casualties. At about 1.30 a.m. on 14 June, the commander of the 5th Marines ordered O Company of the Marines, to withdraw in order to stand in reserve. O Coy's rest in reserve wasshort lived and in the early hours of 14 June the platoon commanders were instructed to put the platoons on one hour's notice to move.
Meanwhile, to the north of Mount William, Marine Sub-Lieutenant Eduardo Villarraza's N Company of the 5th Marines (N/BIM5) occupied Mount Tumbledown. At 10.30 p.m., they were attacked from Goat Ridge by 2nd Scots Guards. About 300 metres from the first Argentine position, the Marines opened fire with MAG machine-guns and FAL rifles. Both British forward platoons started to take casualties and the Scots Guards retreated to the western rocks and reorganized themeselves. Argentine shells began landing among the Guards but by 2.30 a.m., part of the high ground was in British hands and the situation of the Argentine forces became uncertain. In the centre of the mountain, one Scots Guards platoon managed to secure a small piece of high ground, where they were able to set up a fire base that pinned down several Marine positions for the remaining five hours of the battle. Commander Robacio ordered Marine Sub-Lieutenant Eduardo Villarraza to send a fighting patrol to deal with the fire base. Marine Sub-Lieutenant Hector Miño with 5th Platoon accompanied by Second Lieutenant Augusto La Madrid (Argentine Army) with 3rd Platoon. Meanwhile members of the Marine N Company (N/BIM5) were ordered to remain under cover during a bombardment by Argentine artillery. However, using the cover of British artillery, the Scots Guards advanced upon the Argentine positions. Marine Private Jorge Sanchez, in the book 5th Infantry Brigade in the Falklands (Leo Cooper, 2003), recalled:
The fighting was sporadic, but at times fierce, as we tried to maintain our position. By this time we had ten or twelve dead including one officer [Second Lieutenant Oscar Silva, Argentine Army]. I hadn't fired directly at a British soldier, as they had been too hard to get a clear shot at. I can remember lying there with all this firing going over my head. They were everywhere. The platoon commander [Marine Sub-Lieutenant Carlos Daniel Vazquez] then called Private Ramon Rotela manning the 60 millimetre mortar and Rotela fired it straight up into the air so that the bombs landed on ourselves. At this point I had been up and in actual combat for over six hours. It was snowing and we were tired. Some of the guys had surrendered, but I didn't want to do this. I had only twenty rounds left and I decided to continue the fight from Mount William. I popped up, fired a rifle grenade in the direction of 8 to 10 British soldiers to keep their heads down, and then ran for the 2nd Platoon. I can remember saying some type of prayer hoping the British wouldn't shoot me in the back.
Two Argentine platoons (Second Lieutenant La Madrid and Marine Sub-Lieutenant Miño) on the eastern of Tumbledown counter-attacked but were outmanoeuvred by the Scots Guards. During this action Miño was wounded but refused medical assistance until all the wounded men received medical attention.
The fall of Wireless Ridge and the heavy expenditure of artillery, mortar and machine-gun ammunition in support of the 7th Infantry Regiment (RI7) on the ridgeline overlooking Moody Brook rendered the situation of the Marines tenuous. Using armour-infantry-co-operation the 2nd Battalion the Parachute Regiment had advanced through the RI 7 companies. O Company, BIM 5 (O/BIM5) had been sent up to the Moody Brook area and moved into blocking positions to the south and east of Moody Brook. In due course firing broke out in the direction of Battalion HQ at Moody Brook, indicating that the British had outflanked their position. At 7 a.m., the Commanding Officer of the 5th Marines reported his command post near Moody Brook had come under enemy fire from Wireless Ridge. By dawn the approach of the Gurkhas, advancing to secure Mount William was detected.
As the Marine commanders on Tumbledown and Mount William awaited reinforcements, they received orders to withdraw. Ignoring these orders, the Marines continued to resist. By 9 a.m., the Marines had again been ordered to withdraw. Around eight RI 6 personnel were killed and eighteen captured, many of them wounded but the 5th Marine Battalion's N Coy (N/BIM5) carried out an orderly withdrawal to Sapper Hill. The 6th Regiment's B Coy (B/RI6) successfully withdrew with its portable weapons to set up defensive positions around Sapper Hill. Five of the Marine platoon positions now fell to the British. About 9 a.m. Gurkhas, supported by artillery fire, launched the final assault against Mount William.
By 10.a.m. the 5th Marine Battalion's position had stabilized. The Argentine commanding officer, Marine Commander Robacio and the RI 6 Officer, Major Jaimet were determined to continue fighting. In the battle report Marine Commander Robacio wrote: "I was convinced that we could still resist, and that is why I ordered the O Company - which was ready - to begin a counter-attack together with the M Company. I planned to direct this attack myself personally." (Marine Rear Admiral Carlos Büsser, El BIM 5 en las Malvinas, Boletin del Centro Naval, pp. 318-319) .
Generals Mario B. Menendez (the commander of the Argentine garrison) and Oscar Jofre (commander of the 10th Brigade, responsible for the defence of Stanley), following a quick conference, agreed that to continue resistance would entail senseless loss of life. By 1 p.m., the 5th Marines had initiated their withdrawal, after destroying vehicles and heavy equipment. Minutes later Marine Midshipman (naval rank equivalent to second lieutenant) Alejandro Koch's 3rd Platoon, M Coy (M/BIM5) covering the withdrawal of the Marine battalion were attacked by C Company of 40 Commando (C/40 Cdo.) landing frin eight Sea King helicopters. (Hugh Bicheno "Razor's Edge" pg. 314)
Three Argentine Marines (Marine Conscripts Roberto Leyes, Eleodoro Monzon and Sergio Robledo) were killed covering the last withdrawal. Four Royal Marine Commandos were shot in the action (two more, including Lt. Cooper, later trod on mines).
Marine Commander Robacio, commanding the Marine battalion, spoke to British journalists after the war and said, "At about seven o'clock I received the order to withdraw prior to a surrender. Our military code states that for an Argentine military unit to surrender it must have spent all its ammunition or lost at least two-thirds of its men. It was awful to have to ask the units which were still fighting to withdraw." (Michael Bilton & Peter Kosminsky, Speaking Out: Untold Stories from the Falklands War, p. 213, Andre Deutsch, 1989)