Celtic military leader Brian Boru (ca. 940-1014) was the first king of a united Ireland.

Through shrewd military acumen Brian Boru became the first king of a united Ireland, in an era when the isle was little more than a verdant home to Celtic peoples whose society still reflected much of the traditions of the late Iron Age. During his reign, domestic political stability invigorated Ireland, and religious and cultural life was able to flourish. "Brian Boru was remarkable in the Ireland of his time," wrote Máire and Liam de Paor in Early Christian Ireland, "because he seems to have thought in terms of the feudal organization which had already developed in Europe rather than in terms of the primitive and unstable kingship-system of Ireland." His achievement has earned him comparisons with another great uniter of warring lands, the Holy Roman Emperor Charlemagne.

Ireland Before Brian...