Thousands of Irishmen who fought and died in World War I were remembered at a special mass at the Pro Cathedral in Dublin.
The mass, celebrated by Archbishop Diarmuid Martin, marks the centenary of the outbreak of the war.
The Government was represented by Minister for Foreign Affairs Charlie Flanagan.
Members of the Royal British Legion Ireland, along with representatives of the Organisation of National Ex-servicemen, members of the Defence Forces and members of An Garda Síochána were also in attendance.
At the start of the mass, the standards of a number of regiments that fought in WWI, The Royal Dublin Fusiliers, and the Royal Airforce were paraded to the top of the cathedral.
Dr Martin said people owe it to the memory of those who fought and died in World War I to keep peace alive in a troubled world.
But he said that the industrialisation and commercialisation of war continues.
In his sermon, Dr Martin said war had not gone away.
He said the world is witnessing a spiral of violence all over the Middle East and beyond.
Dr Martin said the past month would be remembered as one of the most striking months of blood in recent years.
People see the carnage caused by weapons and rockets especially among civilians and children, and each of these weapons had been designed, built and sold for a profit, he said.
Dr Martin described war as a journey down a one-way street.
He said once people start the journey they almost inevitably establish a further momentum which is self-perpetuating.
Dr Martin said the world's remembering of WWI and those who gave their lives in it must challenge everyone to do all in their power to work for peace.