President Michael D Higgins has described a national sorrow that soldiers who fought in the First World War and their families were shunned for decades in their home country.
Unveiling the first Cross of Sacrifice ever erected in the Republic of Ireland to servicemen and women killed in both world wars, Mr Higgins said the disrespect could not be undone although they are honoured now.
"And we offer our sorrow too that they and their families were not given the compassion and the understanding over the decades that they should have received," he said. "The suffering visited upon our own people at home had perhaps blinded our sight and hardened hearts in so many ways."
Hundreds of thousands of Irishmen and women served with the British and Commonwealth armed forces during both world wars. As many as 60,000 Irishmen and women were killed in combat.
Until today, Ireland was the only country in the world with sizeable war dead graves that did not have a Cross of Sacrifice.
The memorial was erected in Dublin's Glasnevin Cemetery, the country's largest burial ground and resting place to many of the State's founding fathers.
It is the latest milestone in recent official recognition of Irish citizens who fought in the wars, and who for decades were forgotten, pilloried and blacklisted for joining the British armed forces.
It marks the 100th anniversary of the outbreak of the Great War.
The dedication ceremony, including a military band made up of both Irish and British armies, was also attended by UK representatives including Northern Ireland secretary of state Theresa Villiers and Prince Edward, the Duke of Kent.
Government ministers Jimmy Deenihan and Heather Humphreys were also in attendance.
The Duke of Kent said it was an important step in the continuing process of remembering those who died.
"It represents a lasting tribute to their sacrifice and it is my hope, in the years to come, that memorials such as these continue to inspire successive generations to remember," he said.
President Higgins added that it was not appropriate to question the reasons for Irish men and women to enlist for the British Army during the conflict, at a time when many were mobilising to fight for Irish independence.
Urging an end to terms such as "the enemy" and "us" in relations between both countries, he said a better understanding of Ireland's role in the war has deepened a sense of empathy with Britain.
"The ability to share sombre and profound national memories is an important statement and act of friendship and respect," he said.
"As friends we, Irish and British, share this moment of remembrance; and in mutual sympathy we dedicate this monument to the memory of all those who lost their lives during the too long, dreadful years of 1914 to 1918."
There are more than 3,000 world war dead buried or commemorated at 670 locations in the Republic.
The majority were casualties who died in the UK and were taken home for burial by their families.
But there are also many who lost their lives in ships torpedoed and sunk in the Second World War and whose bodies were washed ashore.
It is estimated around 210,000 Irishmen served in the British forces during the First World War, with many Irish descendants serving with other allied forces.
As many as 50,000 Irishmen died in the war.
In the Second World War, up to 100,000 Irishmen served and some 10,000 were killed.
Around 1,000 civilians were killed during air raids.
The Cross of Sacrifice is erected in cemeteries around the world with the graves of 40 or more war dead.
It represents the faith of the majority and the human sacrifice of all Commonwealth war dead, according to CWGC, which maintains the graves of 1.7 million servicemen and women who died in the conflicts.
Ms Villiers said the high level attendance from the UK and Ireland clearly shows a commitment to working together to mark the centenaries of the First World War and other upcoming significant centenaries across the island of Ireland.
"It is important that we use every opportunity to raise awareness of the shared history between the UK and Ireland and between the communities on both sides of the border," she said.
"It is fitting that they now have access to a site where they can come together in quiet contemplation to pay tribute to the memory of those who gave so much for our freedom."