The borders of the kingdom were now safe; its worst elements of disorder were suppressed; and the bishops and barons had taken an oath of allegiance to his son William, and in case of William's death to the infant Henry, born in February 1155. When Henry was called abroad in January 1156, he could safely leave the kingdom for a year in the charge of Queen Eleanor and of the justiciars. His return was marked by a new triumph. The death of David and the succession of his grandson Malcolm, a boy of twelve years old, gave opportunity for asserting his suzerainty over Scotland, and freeing himself from his oath made in 1149 at Carlisle to grant the land beyond the Tyne to David and his heirs for ever. Malcolm was brought to do homage to him at Chester in June 1157, and Northumberland and Cumberland passed into Henry's hands. Malcolm and his successor William followed him in his wars and attended at his courts, and whatever Henry's actual authority might be, in the eyes of his English subjects at least he ruled to the farthest borders of Scotland. He next turned to the settlement of Wales. The civil war had violently interrupted the peaceful processes by which Henry I. sought to bring the Welsh under English law. The princes of Wales had practically regained their independence, while the Norman lords who had carved out estates for themselves along its borders, indignant at Stephen's desertion of them, and driven to provide for their own safety, had formed alliances by marriage with the native rulers. Henry had, in fact, to reconquer the country, and to provide safeguards against any military union between the feudal lords of the border and its hostile princes, Owen Gwynneth of the North, and Rhys ap-Gryffyth of the South. In 1157 he undertook the first of his three expeditions against Wales. His troops, however, unused to mountain warfare, had but ill success; and it was only when Henry had secured the castles of Flintshire, and gathered a fleet along the coast to stop the importation of corn that Owen was driven in August to do homage for his land. The next year he penetrated into the mountains of South Wales and took hostages from its ruler, Rhys-ap-Gryffyth; "the honour and glory and beauty and invincible strength of the knights; Rhys, the pillar and saviour of his country, the harbour and defender of the weak, the admiration and terror of his enemies, the sole pillar and hope of South Wales."