THE STORY the story of British-army prisoners of the Japanese in the second World War has been understood* through the film Bridge Over the River Kwai, in which Alec Guinness played the role of Col Nicholson. In the film, the colonel collaborates with the Japanese efforts to build the bridge, in the hope of winning better treatment for his men – up to, and including, betraying a bid to destroy it.

The reality was different. The river to be crossed was the Khwae Noi, the “little river”, though the Thais renamed it to match the Hollywood creation after the film became an international success.

Hundreds, including six Irishmen, worked under pain of death to build it, according to Robert Widders's latest work, The Emperor's Irish Slaves: Prisoners of the Japanese in the Second World War, which is published by the History Press. They were among 650 Irish serving in the British army to fall into Japanese hands. In the years that followed, a quarter of them died; often from illness, but at times from brutal execution, including crucifixion.

Despite the near-impossibility of escaping through the jungle to safety, some tried, including Fusilier Timothy Kenneally from Bishopstown, Co Cork, and Pte Patrick Fitzgerald, from Kilmeaden, Co Waterford, and two others.

A fifth, Cpl Thomas Finn, from Mitchelstown, Co Cork, serving in the First Battalion Manchester Regiment, was shown the rations that had been gathered for the bid, including tinned fish and concentrated soups, and offered a place.

“We turned down the offer for the following reasons: no map, no compass, [and] as we were proceeding further up country, [working] with the Japs, when we reached top camp it would be time enough to start then,” he said.

The four escaped in March 1943, though they were captured two weeks later by Thai police after a confrontation during which they shot one of the police. The Japanese brought the Irishmen back to their camp at Tha Kilen to be executed.

In post-war testimony, Sgt George Priestman recounted that the four were marched out beyond a railway line shortly after 7am on March 27th. A volley of shots, followed by single revolver rounds, was heard after nearly two hours. Later, when Priestman investigated, he found four seven-feet-tall bamboo crosses. A soldier was tied to one of them, his arms outstretched. He had been shot. Nearby, three graves held the remains of the others.

William Perrot, from Askeaton, Co Limerick was beaten and starved before he and others were forced to dig their own graves and then massacred.

Wing Commander Harold Maguire, from Co Clare, was captured on Java, although his wife had to resort to posting a newspaper advert saying she would “gratefully” receive information from other soldiers about her husband. In July 1945 she received a postcard from him in which he told her his health was excellent: he had to write that to ensure that the postcard was accepted by the Japanese for dispatch to the International Red Cross.

In October 1942, 600 Royal Artillery soldiers were loaded on to a former coal ship at Singapore docks, crammed below deck with no water, and buckets of urine were poured down from above.

Headed for the Solomon Islands, 82 seriously ill men were disembarked en route, at Rabaul, on November 6th, 1942. Just 18 survived, including Lance Bombardier Patrick Ahern from Fermoy, Co Cork, and Lance Sgt Patrick (Nobby) Nolan from Wexford. Despite their illnesses, they were put to work unloading rice.

When one refused to drink urine, he was stripped, covered in animal manure, tied to a tree and left to the mercy of the insects. The next morning, he was killed.

In 1951, the POWs, including the Irish, were offered £76 compensation by the Japanese. Forty years later, during a visit to London, the emperor spoke of his country’s “deep sorrow and pain” for the sufferings endured. This apology did not go far enough, in the eyes of the survivors.

Most of the 650 men joined between 1938 and 1942, and the majority of those came in 1940. After the war, one survivor, Frank McGee from Carrick-on-Shannon, who grew up in a Republican family, was asked why he had joined the British army. He replied: “The English are our enemies and nobody else is allowed to fight them.”

While researching his book, Widders spent days in the National Archives at Kew in London, eventually finding a packet wrapped in greaseproof paper “tucked into the corner of one file”. Inside, he found “a little pile” of death certificates, in which dysentery was the most common cause of death. “The certificates in my hand reeked of torment and death,” he said. Then he folded them and went outside to stand in the Kew sunshine.

*This piece was edited on February 18th, 2012 to correct an error. The error occurred in the editing process.