Llywelyn the Great

Llywelyn ab Iorwerth inherited chaos: after his grandfather Owain Gwynedd died in 1170, two uncles carved up Gwynedd between them. He began his campaign for power young, defeating one uncle and capturing another by 1197, then driving out his cousins at the battle of Arfon on Epiphany 1199. A treaty with King John in 1200 bought him a decade of peace - he married John's daughter Joan in 1205 and absorbed southern Powys in 1208 - but in 1211 John invaded and forced him to surrender everything east of the Conwy. Llywelyn clawed it back within a year, allied with other Welsh princes, then backed the barons who wrung Magna Carta from John in 1215. By 1216 he held dominance across Wales, convening a council at Aberdyfi to parcel out territory to lesser rulers. The Treaty of Worcester with Henry III in 1218 gave him formal standing, and for fifteen years he alternated between skirmishes with Marcher lords and strategic alliances, until the Peace of Middle in 1234 ended his fighting. A paralytic stroke struck him in 1237; he died three years later, leaving his son Dafydd a principality still balanced on the edge.