"Heads down, there are two more incoming," yelled Corporal David Vaatstra down his radio network.

Two mortar shells landed close to his Observation Post on the heights over the Muslim town of Gorazde in Bosnia.

Cpl Vaatstra on the vital observation post above Gorazde

Three hundred Royal Welch Fusiliers had been sent to the Muslim enclave as UN peacekepers.

But on this day, 28 May 1995 , the Serbs began an attack on the UN-declared "Safe Area" and began taking the Welsh soldiers hostage.

The attack against the town was never made public at the time, but the actions of the Welsh soldiers on that day are credited with saving the town.

On the west bank of the Drina River, overlooking the Muslim enclave of Gorazde and its 45,000 Muslim inhabitants, Bosnian Serb soldiers rapidly overpowered the fusiliers.

The Welsh peacekeepers' west bank observation posts high in the towering hills over the town, were sited in the midst of the Serb front line.

These men were outnumbered and outgunned as the Serbs threatened to use heavy weapons and rocket-propelled grenades.

But on the crucial east bank of the river Drina, on the strategically-important heights above the town, another group of Welsh peacekeepers held their own.

"The plan at the time was to hold the observation posts for as long as possible. The Muslims would push through us and take the high ground," said then-Colour Sergeant Peter Humphreys.

In other words, the Welsh fusiliers would defend the key positions, then hand them over to the Muslim soldiers who were rapidly scaling the hills from their homes in the town.

One by one the east bank observation posts became untenable. Eight soldiers were taken hostage at one height.

At a second, Clr Sgt Humphreys was finally given the order to move.

"Seeing thirty heavily-armed Serbs coming towards you, you think, 'it's time to leave this location'," he said.

We had guns in the back of their heads before they knew it.

Clr Sgt Pete Humphreys

"There were rounds coming in from the Serbs. There were rounds coming in from the Muslims.

"There were aircraft overhead, buzzing some of the locations."

His patrol surprised several Serb soldiers in their trenches.

"We had guns in their heads before the knew it."

Then he and his men disarmed them and disposed of their weapons.

He led his men through the only route possible - a minefield - getting them to tread exactly where he trod.

Sgt Humphreys said: "There was a piece of ground that I knew was mined.

"I cleared it by running across the open ground, with the rest of the lads following in my footsteps."

Sgt Humphreys became the second British soldier ever to be awarded the Conspicuous Gallantry Cross for his actions on that and on one previous day.

Meanwhile, Cpl Vaatstra remained on the one height above the town that both the Muslims and the Serbs were determined to take.

They were taking incoming fire

Major Richard Westley

His Observation Post was on a hillside called Biserna - and whoever held Biserna, held Gorazde.

Any artillery targetters working on that height could direct guns to fire any part of the Gorazde - and pulverise the town.

The fusiliers' east bank company commander, Major Richard Westley, could see the Muslim forces moving up the hills to take over the vital observation post.

"They seemed to be really dawdling, and the reason why they were dawdling was because they were taking incoming fire," he said.

But until the Muslim soldiers were close enough, he told Cpl Vaatstra: "You've just got to hold it."

Finally, the first Muslim forces reached the summit and the Welsh peacekeepers began their evacuation - slipping and sliding straight down the mountain-side.

For the next three weeks, the Serbs and Muslims were locked in battle for the town.

Hunkered down

The Welsh soldiers took shelter in cramped underground bunkers.

They were safe from shelling - but trapped - as the battle raged around them.

Then in late June, the assault finally ended. The Muslim forces had held Biserna and the town.

The Serbs moved on to the nearby UN "Safe Area" of Srebrenica, where they massacred 7,000 boys and men.

Several months later, in a classified assessment of the battle, Major Westley wrote that the Royal Welch Fusiliers had prevented a massacre at Gorazde.

He said: "Had we not been there on May 28, Gorazde would have suffered the same fate as Srebrenica."

The British government has never specifically acknowledged the fusiliers' role in defending Gorazde, but on return the battalion was awarded the largest number of peacetime medals since the Korean War.