From an Earldom of some substance in Wales he found him self out of favour with the Angevin King Henry II who ruled England. However the King of Leinster Diarmait Mac Murchada had been kicked out of Ireland by the High King Ruari O’Conner and had appealed to Henry to help him. Henry could not leave France due to his commitments and issued a Royal appeal for his subjects to help the Irish king in any way they could. Richard De Clare saw his chance and offered to help Diarmait regain his kingdom and set about raising an expedition to send to Ireland. In return Strongbow would gain the hand of Diarmait’s daughter Aoife and then succeed to the kingdom of Leinster when Diarmait died.
In August 1170, he landed at Waterford, captured the city, and his wedding to Aoife [above] was celebrated almost immediately in Reginald’s Tower which still stands in the city. Together with the forces of Diarmait Mac Murchada, Strongbow then set out to take the city of Dublin and, having done so, embarked on expansionist raids into Meath. In May 1171, Diarmait Mac Murchada died at Ferns, and Strongbow’s control of Leinster was secured.
From 1172 onwards, Strongbow was titled "earl of Strigoil," which, however, brought him no additional lands. When Henry II came to Ireland to settle its affairs in his favour he removed control of Dublin, Waterford, and Wexford from Strongbow, retaining them for his own use. After military servive in France Strongbow returned to Ireland and campaigned again against the Irish kings. He was appointed Henry’s principal agent in Ireland, and, in that capacity, he issued charters on behalf of the king relating to the now royal city of Dublin. He died unexpectedly in April 1176 from an injury to his foot and was buried in Christ Church Cathedral (the tomb there that is traditionally associated with him is of later date). His funeral presided over by Lorcan Ua tuathail (Laurence O’Toole), archbishop of Dublin. He left as his heir a three-year-old son, Gilbert, and a daughter, Isabella but his wife Aoife wielded power in her own name for a number of years thereafter. The current Monarch of England, Queen Elizabeth II, counts Strongbow amongst her ancestors.
"His complexion was somewhat ruddy and his skin freckled; he had grey eyes, feminine features, a weak voice, and short neck. For the rest, he was tall in stature, and a man of great generosity and of courteous manner. What he failed of accomplishing by force, he succeeded in by gentle words. In time of peace he was more disposed to be led by others than to command. Out of the camp he had more the air of any ordinary man-at-arms than of a general-in-chief; but in action the mere soldier was forgotten in the commander. With the advice of those about him, he was ready to dare anything; but he never ordered any attack relying on his own judgment, or rashly presuming on his personal courage. The post he occupied in battle was a sure rallying point for his troops. His equanimity and firmness in all the vicissitudes of war were remarkable, being neither driven to despair in adversity, nor puffed up by success."