Having climbed from partisan leader to king of armies, Brian Boru eventually established himself as the first monarch of a consolidated Ireland.
In the year 795 some foreigners, called Gentiles in the Chronicles, landed off the coast of Ireland on the island of Lambay, north of Howth, to plunder the shrines. This was the first recorded foreign attack on Ireland, a country then well peopled, with a close network of laws and institutions binding the activities of the tribes and clans. There were bogs and much forest. The lakes of Ireland were large, and the people who lived in the wooden houses were intelligent and strong. They liked poetry, music, history and romantic stories. They liked learning—there were many monasteries and schools, and they loved fighting. Ireland was in touch with Britain, and with the most advanced civilization of the west, France—a letter from Charlemagne to Colgu the Wise of Clonmacnoise written in this year of invasion is still extant.
Centuries of invasion by the Norse had started. Their dragon-boats flying the flag of the raven grounded on the beaches and spilled their men on to the island to bum, murder, and shake the quiet culture and religious foundations laid by Patrick, Colum and their successors. Most successful of the Norse invaders from the fiords of western Scandinavia was Thorkils who expelled the Abbot of Armagh; based his camp at that city and, for fourteen years between 831-845, roamed the island, carrying back church treasure by the cartload to his palace. He fully intended to establish himself as monarch of all Ireland, but was captured by the King of Meath, and drowned in Loch Owel near Mullingar.