The "supremely courageous and inspiring" actions which made a soldier only the eleventh to be awarded the Victoria Cross since the Second World War have been revealed.
Lance Corporal James Ashworth, 23, was killed while storming an insurgent position in the Nahr-e-Saraj district of Helmand province in June last year. He had deliberately exposed himself to fire to land his last grenade.
His mother Kerry, father Duane- himself a former Grenadier- and brother Coran, heard the citation for the award read aloud Aldershot Army base, Hampshire.
It reads: "Despite the ferocity of the insurgent's resistance, Ashworth refused to be beaten.
"His total disregard for his own safety in ensuring that the last grenade was posted accurately was the gallant last action of a soldier who had willingly placed himself in the line of fire on numerous occasions earlier in the attack.
"This supremely courageous and inspiring action deserves the highest recognition."
The Victoria Cross is the most prestigious of all military decorations and only awarded in exceptional circumstances for bravery carried out under direct enemy fire.
First created in 1856, the medal is hand-made from bronze cannon captured from the Russians at the siege of Sevastopol in 1854-55 during the Crimean War.
According to the Ministry of Defence L/Cpl Ashworth and his Grenadier Guards platoon were ordered into Nahr-e-Saraj on June 13 to kill insurgent snipers.
They came under fire as soon as they landed, so he led his team in a 300m charge to the enemy position in a local village.
Two insurgents died in this initial attack but a follow-up assault by Afghan police stopped when a patrolman was shot and killed by the fleeing enemy.
A spokesman said: "With no regard for his own safety, L/Cpl Ashworth again led from the front of his team, advancing on an insurgent compound and using grenades to drive the final remaining enemy to an outbuilding.
"The insurgent was now being supported by fire from several positions, with the enemy desperate to protect their sharpshooter team.
"The immediate priority for L/Cpl Ashworth's team was now to neutralise the final sharpshooter and extract as soon as possible.
"Seeking to break the stalemate using his final grenade, L/Cpl Ashworth dropped to the floor and crawled behind a knee-high wall that ran parallel to the front of the outbuilding.
"With just enough cover to conceal his prostrate form, he inched forward on his belly.
"Bullets flew over his head as he edged forward and the enemy continued to engage the rest of his team.
"When he was within five metres of the insurgent's position L/Cpl Ashworth was desperate to make his last grenade count.
"He deliberately crawled out from behind the wall, exposing himself to fire to get a better angle for his throw.
"L/Cpl Ashworth was now in full view of the enemy just metres away, with rounds hitting the floor just centimetres around him.
"He was preparing to throw the grenade when he was tragically hit by enemy fire."
After L/Cpl Ashworth's death, his company commander, Captain Mike Dobbin said: "Lance Corporal Ashworth was killed while fighting his way through compounds; leading his fire team from the front, whilst trying to protect his men; and he showed extraordinary courage to close on a determined enemy.
"My thoughts and prayers are with his family and his girlfriend, who should be extremely proud of the courage he displayed and the life that he led.
"I am humbled by what I saw of Lance Corporal Ashworth's actions and will never forget him."
Guardsman Jordan Loftus said: "Selfless, brave, courageous - words like these don't come close to what Ash demonstrated that day."
As well as his parents and brother Coran, he left behind sisters, Lauren and Paige, brother Karl and four-year-old niece Darcy, as well as his girlfriend, Emily.
His family paid tribute to him in a statement released after his death, saying: "We are devastated by the loss of our son, brother, uncle and boyfriend.
"He meant the world to everyone and has left an irreplaceable hole in our hearts."
Sergeant Vandell McLean, his platoon sergeant, wrote at the time: "My sorrow is with his family at this time of loss.
"Please take comfort in knowing that Lance Corporal Ashworth died protecting me, his mates and the rest of the platoon."
L/Cpl Ashworth will be the 1,361st soldier to receive the honour, only the second to win the Victoria Cross during the 12-year Afghan campaign.