It was a daring mission behind enemy lines which paved the way for victory in the bloodiest battle of the Falklands conflict.
Captain John Pettinger, of the Parachute Regiment, carried out six reconnaissance operations before the Battle of Mount Longdon.
The retired hero is now selling the Distinguished Conduct Medal he gained for his exploits along with five other medals he gained in his career for an expected £120,000 at auction.
In his Longdon mission, Captain Pettinger used the cover of darkness to identify Argentine machine gun and mortar positions – and even entered enemy trenches undetected.
He later guided the men of B Company in the 12-hour assault and killed three Argentines.
A total of 23 UK and 31 enemy soldiers died in the battle which left the British occupying a key position around the Argentine garrison at Port Stanley in 1982. The fighting ended two days later.
The Distinguished Conduct Medal is second only to the Victoria Cross for acts of gallantry.
Captain Pettinger, 67, is selling it through London auctioneers Dix Noonan Webb next month.
He said: ‘I no longer have any need to wear my full-size medals and now seems the right time to sell them to ensure that they are kept for posterity – and the small part that I played in the Falklands war can be recorded for future generations.’
The money from the sale will help support him in retirement.
The war hero, from Blackburn, joined the Army aged 15 in 1968. He signed up for the Parachute Regiment in 1971 and completed several Northern Ireland tours during the 1970s.
In a transcript being sold with his medals, Captain Pettinger recounts his nerve-wracking work ahead of the assault at Mount Longdon.
He wrote: ‘Numerous enemies were seen and heard, often only a few metres away, and machine gun and mortar positions were found and noted.’
He recalled that all hell broke loose when a British commander stood on a mine which exploded.
He added: ‘The sky turned red with tracer and chaos ensued.’
The sale takes place on September 17.