Turton's "Plantagenet Ancestry." By about 1150 he and his brothers had seized all of Ystrad Tywi and most of Dyfed from the Normans. In 1154 they gained control over Ceridigion. In the years between 1158 and 1163 King HENRY II of England assisted the Marcher Lords in subduing almost all of Deheubarth. Rhys - now the only surviving son - refused to yield and was subjected to several campaigns by HENRY. He was confined to a small area of control.
After 1165, when combined Welsh forces under the leadership of OWAIN AP GRUFFUDD dealt HENRY a major defeat in the Berwyn Mountains and HENRY became immobilized due to his conflict with Thomas Becket, the Archbishop of Canterbury, Rhys was able to regain control over much of Deheubarth.
In 1172 King HENRY II was concerned about the growing power of the Marcher Lords. Even though Rhys had often opposed him, HENRY II offered him the position of the justice of South Wales as he seemed to be the only viable candidate. Rhys accepted. His rights to the areas he had brought under his control were recognized by HENRY II.
Rhys, later in his reign, chose to be referred to as the Prince of South Wales. When Rhys died in 1197 there was a struggle for power between his sons. This caused Deheubarth to cease to be a viable kingdom. Henceforth it would be merely a pawn in the struggle between the King of England and the Prince of Gwynedd or North Wales.