In the ceaseless strife between the old English kingdoms, therefore, it was the personality of the king which was the main factor in determining the hegemony of one state over another. If in the 7th century the successive great Northumbrians--Edwin, Oswald, Oswio and Ecgfrith--were reckoned the chief monarchs of England, and exercised a widespread influence over the southern realms, yet each had to win his supremacy by his own sword; and when Edwin and Oswald fell before the savage heathen Penda, and Ecgfrith was cut off by the Picts, there was a gap of anarchy before another king asserted his superior power. The same phenomenon was seen with regard to the Mercian kings of the 8th century; the long reigns of the two conquerors Æthelbald and Offa covered eighty years (716-796), and it might have been supposed that after such a term of supremacy Mercia would have remained permanently at the head of the English kingdoms. It was not so, Æthelbald in his old age lost his hegemony at the battle of Burford (752), and was murdered a few years after by his own people. Offa had to win back by long wars what his kinsman had lost; he became so powerful that we find the pope calling him _Rex Anglorum_, as if he were the only king in the island. He annexed Kent and East Anglia, overawed Northumbria and Wessex, both hopelessly faction-ridden at the time, was treated almost as an equal by the emperor Charles the Great, and died still at the height of his power. Yet the moment that he was dead all his vassals revolted; his successors could never recover all that was lost. Kent once more became a kingdom, and two successive Mercian sovereigns, Beornwulf and Ludica, fell in battle while vainly trying to recover Offa's supremacy over East Anglia and Wessex. Supremacy of Wessex.