At the only location where Protestant and Catholic Irish soldiers fought as comrades on the British side in August 1917, they will inaugurate a peace tower jointly funded by the Irish and British governments to commemorate Ireland's war dead.
The ceremony, a by-product of the Northern Ireland peace process, would have been unthinkable until recently and marks an end to 80 years of amnesia in the Republic of Ireland about the participation of southern soldiers on the British side.
The round tower, modelled on a 6th-century Irish monastic settlement, was built by young people from both sides of the Irish border, but its most remarkable feature is that it is the result of collaboration between southern Irish politicians and northern Unionists.
British soldiers used to sing nostalgically about being a long way from Tipperary, but one of the best-kept secrets of the First World War is that 210,000 Irishmen volunteered to fight for Britain. Of the 50,000 who died between the Somme and Passchendaele, as many as 30,000 were from the South.
Officially acknowledging, let alone commemorating, the Irish contribution on the British side has long been a source of discomfort in the Republic where the wearing of poppies is still highly controversial. But after 80 years, attitudes are slowly changing.
The tower is the idea of Paddy Harte, a former member of the Irish parliament who was deeply moved by a cross-border visit to the Flanders battlefields. The graveyards were filled with Irish names, Murphys, O'Learys, Ryans, O'Sullivans.
"As a Catholic I was aware that my church had never said a prayer for the men who died in the First World War, nor asked me to," said Mr Harte. "Neither my party nor my state had ever done anything to recognise what happened to our fellow countrymen."
Mr Harte and the former Unionist politician Glenn Barr agreed that if people from both traditions faced up to the tragedy of the war, that could in itself contribute to healing and reconciliation today.
Tom Burke, of the Royal Dublin Fusiliers Association, who is writing a book on the subject, says he has been inundated by letters and calls from people in the Republic whose grandfathers or uncles were in the trenches but whose gallantry received no recognition.
"The official neglect of these people and the pigheaded indifference we have shown to this period is a tragedy. For example, Gloucester Street in inner-city Dublin was practically wiped out in the first German gas attack in May 1915. Yet in the South we airbrushed the war out of our history, and we allowed Unionists to hijack the war as a solely British tragedy. It wasn't, it was a human tragedy."
It would seem, however, that there are some in the Republic who are still not ready to confront the ghosts of Flanders and the Somme. The Irish army band has declined an invitation to take part in a Last Post ceremony at the Menin Gate in Ypres on the eve of the Messines event. The official explanation is that the buglers will be too busy practising for Messines, but privately government sources admit that Irish military presence at a British army monument would be difficult.
"Let's not forget the background. Remembrance and poppies have always been difficult because of the history of the British army in Ireland. Things are changing, but reconciliation is painful for all of us," said one source. The Menin Gate nevertheless contains the names of hundreds of southern Irishmen.
Many of those from southern Irish counties joined up either to escape poverty or because they were lured by the promise of adventure.
Those lucky enough to survive found themselves ostracised when they returned home. The political landscape had been transformed. Ireland was still under British rule, but the 1916 rising had taken place, and its leaders had been executed by British soldiers. Far from being regarded as patriots, some of the survivors were taken out and shot by the IRA.
Today, the Messines Ridge - where in August 1917, Protestants from the 36th Ulster division fought alongside southern Catholics from the 16th Irish - is a prosperous farming region.
Stone used in the peace tower was brought from each of Ireland's 32 counties, and it has been designed so that the sun will enter its chamber every 11 November at 11am.