The victim was hit so hard he was a "dead man" the moment the blow landed, it was claimed.
The court heard that after the assault by former Black Watch soldier Paul McKay there was nothing anyone could do to save Private Mark Connolly, 24.
It is alleged Pte Connolly was killed as the pair celebrated the end of a driving course in Paderborn, Germany, in May last year.
McKay, 25, of Inverkeithing, Fife, has denied manslaughter and affray.
The trial at Catterick Garrison, North Yorkshire, was told both men had been drinking in the Naafi bar and had begun arguing after a wallet was knocked on to the floor.
Oliver Glasgow, prosecuting, said it was the fact that both soldiers, members of the 3rd Battalion, the Royal Regiment of Scotland, had been drinking that led to the argument.
He said: "The argument spiralled out of control and led to the defendant punching Pte Connolly so hard in the face that he died. The blow was not struck in self-defence but in anger.
"Connolly posed no threat to McKay; in fact he did not even raise a fist. He died as a result of the force of the blow.
"The punch was so hard there was nothing anyone could do to save him. He was, in fact, a dead man the moment the punch landed."
The two men had started drinking after finishing a vehicle training course but had a row over Pte Connolly's wallet being knocked to the floor then kicked across the room, scattering coins. Pte Connolly told McKay to pick up the wallet but he refused, the hearing was told.
At one stage, Mr Glasgow told the court martial, the two men were rowing so aggressively that other soldiers thought there was going to be a fight. Pte Connolly was taken into the foyer of the bar by another member of the unit but McKay followed, pushed past the other soldier and punched his friend in the face.
"The force of the blow was such that he fell to the ground straight away," said Mr Glasgow. "The defendant then turned and walked away, not stopping to see if his friend was injured."
Other soldiers in the bar claimed McKay was "ready and willing" to have a fight but he later told investigators Pte Connolly had hit him first and he had struck back.
Mr Glasgow said: "The two men had been rowing so aggressively they had to be parted but Pte Connolly posed no threat. It was the defendant who followed him out of the bar and it was he who initiated the violence. He hit Pte Connolly as hard as he could and hit him so hard that the punch alone killed him."
The hearing was told members of the unit had drunk large amounts of alcohol that day.
Lance Corporal Barry Dougan, who had also been drinking in the bar said the incident involving the wallet was "meant as a joke" but escalated into a heated argument.
He said: "Connolly did not find it funny. I wanted to calm him down, so I offered to take him outside. We went into the foyer and I thought things would sort themselves out. Then I saw a punch thrown but I don't know where it landed."
After the attack, several Dutch soldiers tried to help Pte Connolly but could do nothing to save him.
L/Cpl Dougan, who was also arrested and questioned about the killing, said his memory of what happened had been affected by drink and he suffered a "partial memory block" because of what had happened.
Corporal Morgan Gilbert, who was in the bar but was sober, claimed that after the assault, McKay walked past him and said: "Sorry about that mate".
Later, he saw the defendant sitting with his head in his hands and crying.
The trial continues.