A new book, 'The Fighting Irish: The Story of the Extraordinary Irish Soldier', written by historian Tim Newark, tells the fascinating tale of Irish mercenaries and volunteers fighting on foreign shores down through the centuries.
"The Battle of the Boyne was the real starting point," said Mr Newark.
"As a result of their defeat, many Catholic soldiers sailed abroad to enroll in the armies of the King of France, setting a pattern for future foreign military," explained the author of a number of military histories.
Many more Irishmen set sail with less lofty ideals in mind -- escape poverty, or just to try and make their own way in the world.
The majority took employment with the British Army -- at one time making up over 40pc of Queen Victoria's army in the Boer War.
On the opposing side, John MacBride and Arthur Lynch organised two Irish Brigades -- about 300 men in all -- fighting for the Boers.
It has been estimated that 200,000 Irishmen took part in World War One, among them Corporal Michael O'Leary from Cork, who was awarded a Victoria Cross in 1915 for killing eight Germans.
Given a banquet on his return to Cork, O'Leary's father remained unimpressed, however.
"I often laid out 20 men with a stick coming back from Macroom market, and it is a bad trial for Mick that he could only kill eight -- and he having a rifle and a bayonet," Daniel O'Leary told a local newspaper.
'The Fighting Irish: The Story of the Extraordinary Irish Soldier' by Tim Newark, is published by Constable and is priced at ?16.99.