Mr Ahern was speaking at the unveiling of a memorial to 131 men from Fermoy, Co Cork, and surrounding areas, who died in the war.
His speech comes just days before intensive negotiations between the North’s political parties and the British and Irish Governments are due to get under way at St Andrews in Scotland.
Mr Ahern said it was ‘right and proper’ that the sacrifice of the estimated 49,000 Irish soldiers who died fighting with the British Army in World War I had been brought into national consciousness.
“The men who enlisted early had been sent off with public honour and celebration,” he said.
“Those that survived came back to a very changed Ireland that did not value their sacrifice.
“Those that died in the battlefield came close to being completely forgotten by the following generations. It is right and proper that in more recent times the memory of these men has been resurrected and proper tribute has been paid to them.”
About 140,000 Irishmen enlisted in the British Army during World War I.
Although unionists place great emphasis on the war, and in particular the Battle of the Somme, the event was only officially commemorated in Ireland for the first time earlier this year.
“These men were Protestant and Catholic, unionists and nationalists, but their differences were transcended by a common higher purpose,” said Mr Ahern.
The government’s decision to raise the profile of Irishmen who died in the war is part of an initiative to foster improved relationships with unionists.
Members of the Royal Irish Regiment and the British Legion also attended yesterday’s event.