In early January 1177, he assembled a small army of 22 knights and 300 foot-soldiers and marched north, at the rate of thirty miles a day.

After two fierce battles, in February and June 1177, de Courcy defeated the last King of Ulaid, Ruaidhrí Mac Duinnshléibhe.

He also created a cell for Benedictines at St. Andrews in the Ards (Black Abbey) for the houses of Stoke Courcy in Somerset and Lonlay in France, which was near Inishargy, Kircubbin, in present-day County Down.

The early Irish monastery of Nendrum was given to the Benedictine house of St Bees in Cumberland in order that they might also establish a cell.

His wife, Affreca, founded the Cistercian monastery of Grey Abbey, County Down, as a daughter house of Holm Cultram (Cumberland) in 1193.

John de Courcy returned, sailing across the Irish sea from the Isle of Man in July 1205 with Norse soldiers and a hundred boats supplied by his brother-in-law, Ragnold, King of Mann.

John and his army landed at Strangford and laid siege to Dundrum Castle in vain because the defences he himself had made were too strong.

[5] The story of John de Courcy's defeat of the French champion, and his winning the privilege to remain covered in the presence of the King, appears in Chapter 12 of Mark Twain's The Prince and the Pauper.

Goddard Orpen, the respected historian of the Norman invasion of Ireland, clearly admired this remarkable man who first established a power base in Ulster and then dominated the whole country.