Whether for the "shilling", John Redmond, "little Catholic Belgium" or adventure 140,000 Irish men joined the British army in Ireland. Thousands more Irish men were already serving, or were recruited or conscripted in Britain, Australia, the USA and Canada.
In this extract from the 1966 documentary 'And in the Morning', men who served in the First World War give their reasons for enlisting.
Denis Kelly a veteran of the Irish Guards explains how he ended up joining the army in 1914 when he was living in England.
A desire to see something of the world prompted Jack Campbell to join the British Army. Jack tells Gay Byrne how he was influenced by his elder brother.
Edgar Poulter recalls heading to Lansdowne Road, Dublin, with friends to join what would become known as a pals battalion and paying half a crown for the privilege.
Emmet Dalton outlines his reasons for joining up and describes the initial reaction of his father to seeing his son in a British Army uniform.
A veteran Royal Dublin Fusilier, Jimmy O'Brien, recalls joining the British Army in an office in Grafton Street, Dublin.