The Taoiseach today described his visit to World War 1 memorials in Flanders as "symbolically very important.
It's very striking when you stand there and look at the names of your own country people who fought in what was supposed to be the war to end all wars, and the senseless slaughter that occurred," he said.
Mr Kenny and British prime minister David Cameron conducted a two-hour tour of some of the sites of the most deadly battles of the First World War - almost half a million soldiers died in the Ypres Salient, or frontline, including tens of thousands of Irishmen who fought in the British army.
It is the first time that Irish and British heads of Government have jointly visited the memorials at Messines, and marks a further stabilisation of relations between the two countries.
Among the locations where the two leaders laid wreaths was the grave of Major Willie Redmond, nationalist politician and Member of Parliament in the Irish Parliamentary party. He was commissioned as a captain in the Royal Irish Regiment and fought on the Western Front with the 16th (Irish) Division, in the winter of 1915 to 1916, and died during the Messines Ridge attack in June 1917.
"The thought crossed my mind standing at the grave of Willie Redmond - that was why we have a European Union and why I'm attending a European Council," said the Taoiseach. "It was a great privilege being able to lay a wreath on behalf of the Irish people at the grave of Willie Redmond," he added.
Both the Taoiseach and the prime minister signed a book of remembrance; Mr Kenny wrote: "To honour a soldier who lived and died for his beliefs and whose faith in the power of unity still resonates powerfully." In accordance with his last wishes, Major Redmond is buried outside the cemetery where the other men from his brigade are interred, as a protest against the execution of the leaders of the 1916 Rising.
Mr Kenny and Mr Cameron were then joined by Belgian prime minister Elio Di Rupo for a commemoration ceremony at the Menin Gate in Ypres, where the names of 54,000 war dead are engraved into the walls and archways, including three Irish brothers who served in the Royal Dublin Fusiliers.