Norman invasion of Ireland
In 1166, the exiled King Dermot of Leinster tried to raise a force of Norman knights to re-conquer his lands. He obtained a license to do so from Henry II, and persuaded Richard de Clare, Earl of Pembroke (known as 'Strongbow'), to help him by making Strongbow his heir. He landed in County Wexford on 1st May 1170, and later that year, had re-conquered Leinster. Suddenly, one of Henry's barons was in the position to take a major holding in Ireland, so Henry closed all Irish ports and ordered the Normans home. Strongbow disobeys, Dermot dies the next year, making Strongbow the King of Leinster, and Henry arrives with a large force to control his vassal, and accept the fealty of the Irish nobles.