The immediate cause of the Anglo-Norman invasion was a request for assistance by Diarmait Mac Murchada (Dermot MacMurrough), the King of Leinster. After being exiled by a coalition of rival Irish kings around 1166, Diarmait sought help to reclaim his throne. He turned to Henry II of England, who allowed him to recruit Anglo-Norman knights and mercenaries.

This request was part of a broader context of increasing Norman expansionism following their conquest of England in 1066 and subsequent advances in Wales and Scotland. The Normans were experienced warriors and administrators, and Ireland presented a new opportunity for conquest and settlement.

The Invasion and Early Campaigns

The initial invasion began in 1169, led by Richard de Clare, known as Strongbow, a Norman lord with close ties to Diarmait. Strongbow and his forces landed in Wexford and rapidly advanced inland. They captured key towns and castles, gradually establishing a foothold.

In 1170, Strongbow married Diarmait’s daughter Aoife, solidifying his claim to the kingship of Leinster. With increasing successes, the Normans expanded their control into other parts of Ireland.

Henry II’s Intervention

Alarmed by the growing power of his vassals in Ireland, Henry II personally led an expedition to Ireland in 1171. This marked the first time an English king set foot in Ireland. Henry aimed to assert his authority over the Anglo-Norman lords and establish direct royal control.

He was declared Lord of Ireland, and the papal bull Laudabiliter—allegedly issued by Pope Adrian IV—was used to legitimize English rule over Ireland as part of a Christianizing mission.

Henry’s arrival set the foundation for centuries of English governance in Ireland, although his control was initially limited mostly to areas around Dublin known as the Pale shutdown123