Lieutenant James Adamson was awarded the Military Cross after killing two insurgents during close quarter combat in Helmand's notorious "Green Zone".
The 24-year-old officer, a member of the 5th battalion The Royal Regiment of Scotland, revealed that he shouted "have some of this" before shooting dead a gunman who had just emerged from a maize field.
Seconds later and out of ammunition, the lieutenant leapt over a river bank and killed a second insurgent machine-gunner with a single thrust of his bayonet in the man's chest.
The officer was one of 145 members of the armed services who last week received awards in the latest Operational Honours list.
In a graphic description of the intense fighting in Helmand, the officer told of the moment killed the second fighter. He said: "It was a split second decision.
"I either wasted vital seconds changing the magazine on my rifle or went over the top and did it more quickly with the bayonet.
"I took the second option. I jumped up over the bank of the river. He was just over the other side, almost touching distance.
"We caught each other's eye as I went towards him but by then, for him, it was too late. There was no inner monologue going on in my head I was just reacting in the way that I was trained.
"He was alive when it went in – he wasn't alive when it came out – it was that simple."
Recalling his feelings in the moments afterwards Lt Adamson, said: "He was young, with dark hair. He only had kind of whispy hair on his chin, not a proper beard, so he wasn't that old, maybe a teenager.
"Afterwards, when he was dead, I picked up his PKM (Russian-made belt-fed machine gun) machine gun and slung it over my back.
"We then had to wait for more of my men to join us. We thought there could be more Taliban about and we were just watching our arcs of fire, waiting for more to come out of a big field of maize which came right up to the river we had been wading through.
"One of my men, Corporal Billy Carnegie, reached us, looked at the two dead Taliban on the ground and then saw the blood on my bayonet and said "boss what the **** have you been doing?"
The firefight, in July 2008, began during the middle an operation to push the Taliban out of an area close to the town of Musa Qala in northern Helmand.
Lt Adamson's platoon of 25-men, which was leading the assault, had just halted their advance when they were attacked.
Lt Adamson, who is single and comes from the Isle of Man, was moving between two eight man sections when a group of Taliban fighters attempted a flanking attack.
He continued: "The Taliban kept on probing us – sending in fighters to attack, first in twos then in fours.
"There was a gap between the two sections and the Taliban realised this and were sending in men to get between the two groups so they could split us up and isolate us.
"Myself and Corporal Fraser 'Hammy' Hamilton were wading nipple deep down a river which connected the two positions. Hammy was ahead when the Taliban fighter with the PKM (Russian machine gun) appeared from a maize field.
"There was an exchange of fire and 'Hammy' fired off his ammunition and then the weight of fire coming from the Taliban forced him under the water.
"The machine-gunner had also gone to ground but was still firing in our direction periodically. I had just caught up when 'Hammy' came up out of the water like a monster of the deep.
"Then another Taliban man came through the maize carrying an AK47. He was only three to four metres away.
"I immediately shot him with a burst from my rifle which was already set on automatic. He went down straight away and I knew I had hit him.
"Hammy said I shouted: 'have some of this' as I shot him but I can't remember that. I fired another burst at the PKM gunner and then that was me out of ammunition as well.
"That was when I decided to use the bayonet on him. It was a case of one second to bayonet him or two seconds to put on a fresh magazine.
"Nothing was really going through my mind but briefly I did think 'if this works out the boys will love it' – as in the rest of the platoon that I commanded.
"The undergrowth is so dense in the 'Green zone' that I often ordered bayonets fixed because you knew the distances between you and the Taliban could be very short. It is also good for morale."
His Military Cross citation read: "Adamson's supreme physical courage, combined with the calm leadership he continued to display after a very close encounter with the Taliban, were of the very highest order.
"His actions also neutralised an enemy flanking attack which could have resulted in casualties for his platoon."
Two weeks earlier Lt Adamson had won a Mention in Dispatches (MID) by leading his men in an ambush against the Taliban in the same area.
It is understood that the young lieutenant is the first member of the armed forces to receive two awards for gallantry during the same operational tour.
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