Before the world erupted in war in 1914, Ireland itself was on the edge of civil war. But it was an MP in the House of Common named John Redmond who argued to the southern Irish Roman Catholics that “ the interests of Ireland – of the whole of Ireland – are at stake in this war.” He made the argument at Woodenbridge in September 1914. He pledged his support for the Allies cause. Like Reagan who imagined the left and the right would be unified when faced with an opponent form another world, so too the First World War brought 200,000 Irish soldiers to the recruitment tables in Dublin and swore out an oath to the King. They fought to preserve an empire that they intended to part ways with.
Each Irish soldier had to swear out this oath of allegiance: “I, do swear by Almighty God that I will be faithful and bear true Allegiance to His Majesty King George the Fifth, His Heirs, and Successors … So help me God.”
The Royal Dublin Fusiliers represented themselves well in the Battle of the Somme in September 1916. They managed to capture the town of Guillemnont which was occupied by a fortified German division. The Irish Fusiliers also overwhelmed the Germans at Ginchy. It here that wildly popular Irish nationalist Tom Kettle died.
The Irish captured Wyatschaete in the summer of 1917, on the first day of the Battle of Messines. They fought at the Third battle of Ypres and at Flanders Fields. Home Rule would never survive World War I. A militant home grown nationalism instead took its place. In fact, Sinn Fein was another result of the First World War.
The sad irony of Irish fighting for the British in World War I of the war was made bitter when most school in Ireland did not teach World War I at all. And few realize that 50,000 Irish gave their lives for the cause.
Source: Guardian UK, wiki