Although we are not nowadays on good terms, John A Murphy did not hesitate to contact me last Friday with the shocking news that the Canadian historian Peter Hart, author of that classic of modern Irish scholarship, The IRA and its Enemies, Political Violence and Community in Cork, 1916-1923, was prematurely dead at the age of 46. Because Hart was a hero to both of us.

By some sad serendipity, when Murphy called I was leafing through a beautifully produced book A Great Sacrifice, Cork Servicemen who died in the Great War, by Gerry White and Brendan O'Shea, published by the Evening Echo, which, with a wealth of information and pictures, lists the name of every Cork serviceman who died in that conflict. To Peter Hart fell the grim task of telling us what the IRA did to some of these servicemen's comrades after they came home.

I can still recall clearly the night in 1998 I began to read The IRA and its Enemies. As soon as I saw the heading on the first chapter, 'The Killing of Sergeant O'Donoghue', the hair rose on my head. It concerned the IRA's shooting on Wednesday, November 17, 1920, of Sergeant James O'Donoghue of the RIC, who never carried a carbine, on his way home from Tuckey Street barracks to Tower Street.

Tower Street is just around the corner from where my IRA grandfather, Pat Harris IRA, lived at 11 Nessan Street, making him a neighbour of the murdered man -- I say murdered because my grandfather must have thought so too since he fell silent whenever O'Donoghue's name came up in the long conversations he carried on with his old IRA comrades, and to which I listened avidly as a boy.

Hart's book still causes a bitter reaction among ultra-nationalists. It challenges perceived nationalist wisdom that the IRA did not wage war on ordinary Protestants -- unless of course they were spies. But as Hart shows, the bulk of spies came from within the ranks of the IRA itself -- just as in the Provisional IRA.

Although he stops short of using phrases like "ethnic cleansing", Hart shows there was a strong streak of sectarianism in the IRA's campaign against alleged "spies", a campaign widened to include warnings against ex-servicemen, Jews, disorderly women and what the IRA called the "tramp class".

The culmination of Hart's book is a chapter titled 'Taking it Out on the Protestants'. This tells the story of the Dunmanway massacre of April 25, 1922, when members of the IRA pulled 10 ordinary Protestant shopkeepers, farmers and clergymen from their beds and shot them in cold blood, an atrocity movingly re-visited by RTE in a recent documentary Cork's Bloody Secret.

Hart's account makes it clear that the IRA campaign tore the Protestant heart out of Cork city and county. "Thousands more left permanently in 1921 and 1922, rapidly reducing the population of Cork to half its pre-revolutionary size. Those who stayed were frequently subjected to a regime of boycotts, vandalism and theft. Most of these people returned within a few months but many did so only to settle their affairs, sell their land and leave for good."

Who were these persecuted Protestants? Anglo Irish landlords, as nationalists like to believe? No, Hart says, they were just like their Catholic neighbours. "They came from a variety of stations of life: businessmen, farmers, a lawyer, a curate, a post office clerk, a farm servant. None were poor save James Greenfield, and a few were quite prosperous. Most lived somewhere in between, in middling circumstances."

As Hart shows, these sectarian incidents were not confined to Cork. Future historians may provide a fuller picture county by county. But the results were the same all over southern Ireland: the enforced exodus of at least 60,000 ordinary Irish Protestants, which deprived town and country of some of its most decent and productive citizens and left us culturally and socially poorer.

Hart sums up why we let it happen. "Beneath the welter of pretexts and suspicions, beneath the official rhetoric of courts martial and convictions, the IRA were tapping a deep vein of communal prejudice and gossip: about grabbers, Black Protestants, and Masonic conspirators, dirty tinkers and corner boys, flyboys and fast women, the Jews at No 4 and the disorderly house at No 30."

Hart uses the IRA's own account of the shooting of Mick Sullivan, a street singer and cattle drover, to make a poignant point about what happened to the wrong "type" in the eyes of the IRA. "He was a very raggedy individual a kind of tinker and hard nail. We were up early in the morning and there were hailstones. They brought on the spy, but I heard one shot only. A placard was pinned on him (Spies and Informers Beware)."

Tragically, hundreds of Cork servicemen came home to find themselves objects of suspicion. As Hart says: "The IRA pursued the same 'types' in 1922 and 1923 as they had in the Tan war -- 44 per cent of civilians shot by the IRA after July 1921 were Protestant and 20 per cent were ex-soldiers.

For most of my life, these forgotten victims lived at the margins of public memory. Peter Hart's monumental achievement was to dig up these buried bodies. Without such a reckoning there can be no reconciliation, and the conscience of a country can never be fully at peace. In that light, John A Murphy's raw reaction to Hart's death in his email to me deserves to be quoted in full.

"Wherever one stood in the debate, Hart was an original, a pioneer -- coolly challenging accepted nationalist narratives, the personification of history as critical investigation versus history as unchallengeable tablets of stone. Signs by, he incurred the venomous hostility of An Phoblacht et al. He was unflappable, charming and brave. But I don't have to tell you. At 46, he is a bright light, prematurely quenched. I hope his erstwhile opponents will have the generosity to acknowledge that."

So do I, but I doubt that they will do so. Both Kevin Myers and myself believe the savage polemics directed at the physically frail Hart by ultra-nationalist lobby groups took a toll on this mildest of men.

Hart was an historian with no axe to grind except the blade of truth. But judging by the Wikipedia entry on the Bandon Valley massacre, adjusted regularly by his ultranationalist opponents, they have forgotten nothing and learned nothing.

The egregious entry runs as follows -- I have italicised the weasely words: "The Dunmanway massacre was the killing of 10 Protestants, mainly informers but also including two relatives of informers, and the disappearance and presumed death of another three in and around Dunmanway, Co Cork, between April 26 and April 28, 1922."

Peter Hart's name will be still revered by new generations of Irish historians, when these weasel words are long forgotten. A Canadian by birth, he will be forever an honorary Irishman by virtue of his sterling service to this State: he told us the truth that sets us free. Ar dheis De go raibh a anam uasal.

Eoghan Harris

Sunday Independent