How did Dermot MacMurrough retake Dublin in 1170?

Dermot MacMurrough, the exiled king of Leinster, retook Dublin in 1170 by enlisting the military support of Anglo-Norman adventurers from Wales.12

After being driven from Ireland in 1166 by the high king, Roderic O’Connor, and his Norse allies, Dermot secured permission from King Henry II of England to recruit mercenaries. He returned to Ireland in 1167 to establish a foothold and was later joined in August 1170 by a significant force led by Richard FitzGilbert, 2nd Earl of Pembroke, commonly known as Strongbow. With the aid of these Anglo-Norman forces, Dermot successfully captured the city. To solidify this alliance, Dermot married his daughter, Eva, to Strongbow, who subsequently succeeded him as the ruler of Leinster.123