Past wounds meet present conflict as Dublin celebrates 90th anniversary of Easter Rising

In a milestone event replete with historical and political significance, the Irish authorities will - on Easter Monday - stage a major commemoration of the armed insurrection that triggered the ending of British rule. Thousands of members of the Irish army and other defence forces will mark the 90th anniversary of the 1916 Easter Rising by parading through Dublin while the Air Corps stages a fly-past.

The immediate significance of the event is that it has not been held in recent decades for fear of giving credence to the IRA campaign of violence. But, following the run-down of the Troubles, the Easter Rising has assumed an important new place, as Irish nationalism and republicanism undergo realignments.

The conventional political parties are locked in controversy over who are the true heirs of the rebellion, attempting to wrest any sense of ownership of the violent event away from the IRA and Sinn Fein. The President of Ireland, Mary McAleese, has pitched into the debate, praising "the sacrifices of the heroes of 1916" who rescued the country from being one of Britain's "captured dominions". Not for the first time, the stuff of history has become the stuff of present-day political dispute.

The GPO, one of the most prominent buildings in O'Connell Street and the focus of the fighting in 1916, is to be transformed into a national monument, part of a whole array of projects in the run-up to the centenary in 2016. Monday's march-past of the GPO is the revival of a practice that was abandoned in the early 1970s after the eruption of the Troubles. This is no mere gesture of ritual respect. It is a crucial part of a new battle for the title deeds of Irish republicanism.

The Irish political establishment is embarking on a campaign to wrest the republican mantle back from Sinn Fein and the IRA, which have largely commandeered the term. Irish Prime Minister Bertie Ahern received sustained applause when he recently declared: "The Irish people need to reclaim the spirit of 1916, which is not the property of those who have abused and debased the title of republicanism. We in this state will proclaim our republicanism. We will recognise and praise the vision of the volunteers of 1916."

The outcome of this new, unarmed, struggle is destined to have important effects on Irish politics. With the IRA campaign over, many observers believe Sinn Fein will reap an electoral harvest. Its declared ambition is to increase its seats in the Irish parliament from five to 14. Senior figures in other parties do not discount that, worrying that it could hand Sinn Fein the balance of power in the Dail.

The six-day 1916 siege of the GPO arguably changed the course of Irish history, leading as it did to British withdrawal, the south's independence and the creation of Northern Ireland. The rising began unpromisingly, with a confusion of orders and counter-orders which meant that many potential rebels simply stayed home. Fewer than 2,000 turned out, taking over a number of buildings in central Dublin.

Their headquarters was the GPO, which was barricaded by a few hundred volunteers who had marched to it in uniform. The chief of the insurgents, Padraig Pearse, stood on the GPO steps and solemnly proclaimed a Republic. He announced: "We declare the right of the people of Ireland to the ownership of Ireland, and to the unfettered control of Irish destinies, to be sovereign and indefeasible." The same proclamation will be read out on Monday.

The authorities were taken by surprise but reinforcements were quickly brought in and artillery was deployed, with a British gunboat moored on the Liffey blasting away at the GPO. Within a short time, it was reduced to a shell, the position of the rebels rendered hopeless.

After six days Pearse signed a formal letter of surrender "in order to prevent further slaughter of the civil population". The death toll was 64 rebels, 132 security forces and more than 300 civilians. Following the surrender the whole episode seemed over, but unexpectedly a military fiasco was transformed into a political watershed. While Pearse and his men saw themselves as soldiers following the rules of war, British and Unionist opinion regarded the rebellion as treachery at a time when Britain was locked in the First World War. The authorities imposed martial law, ordering thousands of arrests and transporting hundreds to a camp in Wales. Critically, 15 rebel leaders, including Pearse, were executed by firing squad, producing a wave of outrage.

The subsequent surge of pro-rebel sympathy affected many who had disapproved of the rising. The importance of the event was captured by the poet W B Yeats, who wrote: "All changed, changed utterly: a terrible beauty is born." Ironically, Sinn Fein, then a small grouping, was not involved in the rebellion. But the authorities christened it "the Sinn Fein rising" and the title was afterwards adopted by the separatist movement.

Pearse and others who were executed, such as the socialist James Connolly, achieved instant martyrdom and lasting cult status as the founding fathers of the new Irish state. Those who survived the pounding of the GPO included major figures such as Michael Collins, later killed in the subsequent civil war, and others who went on to head Irish governments.

The modern Irish state thus had its origins in a tumultuous period which began with the seizure and siege of the GPO. As columnist Kevin Myers put it: "All our political parties were born out of the barrel of a gun." For decades, nationalist Ireland felt no shame or guilt in that, agreeing with one commentator's assertion that the rebellion "was a brave, clean fight against an empire, its protagonists deserving all honour". But when the most recent troubles broke out, unease grew as the IRA argued its killings followed hallowed precedent and it was the legitimate heir to 1916.

With the ending of the Troubles the sense is that 1916 and the GPO can be commemorated in a less inhibited way. Modern Ireland has become steadily less ideological and more pragmatic. But the past still exerts a strong hold on the Irish imagination. Sinn Fein's leaders are determined to maintain a grip on the past in order to grasp the levers of power in the future. The Irish political establishment is determined to thwart them. The scene is set for the second battle of the GPO.