Thus the breaches of the peace by the French recoiled terribly upon themselves, and they suffered vastly greater loss than they had inflicted upon the English. From the time when he let slip the opportunities, both of joining Hotspur and of falling on the royal army after their victory, Glendower's power declined. For a time he continued to capture castles, and to carry out raids across the border, but gradually he was driven back to his mountain strongholds. His followers lost heart. He became a fugitive, and died on the 20th of September, 1415, in the sixty-first year of his age, at the house of one of his married daughters, whether at Scudamore or Mornington is unknown. Mortimer died in Harlech Castle, during the time it was besieged by the English. It is said that his death was caused by depression and grief at the misfortunes that had befallen him. The Earl of Northumberland, as John Forster had anticipated, raised the standard of revolt in 1405, in concert with the Archbishop of York and some other nobles; but before he could join these with his forces, they had been forced to surrender to the king, who had marched north with a great army. The archbishop and some of his associates were executed, and the earl, finding himself unable to oppose so great a force, fled into Scotland. Alnwick surrendered without resistance, and Warkworth after a siege of eight days. Berwick was captured, and its governor and several knights executed. Escaping from Scotland, where he feared that he might be seized and surrendered to England, the earl sailed to Wales, and for some little time stayed with Glendower; then he crossed to the Continent, and in 1408 landed in Yorkshire and again raised his standard. The sheriff of the county called out the levies, and attacked him at Branham Moor, where the old earl was killed and his followers defeated. In 1415 the king, being on the eve of war with France, and anxious to obtain the goodwill and support of the Northumbrians, restored Hotspur's son, who had been for years a fugitive in Scotland, to the estates and honours of his father and grandfather. Fortunate it was, for Oswald, that the capture of his fellow conspirators caused the earl to retreat, in 1405, without giving battle. The young knight had, at his summons, called out his tenants, and with them and his retainers had joined Percy. As soon as the latter decided to fly to Scotland, his force scattered, and Oswald returned home with his following. He took no part in the final rising. Before this took place he had married his cousin, Janet. His father lived to be present at the wedding, but died the following year; and, in accordance with his wishes, Oswald took up his abode at Yardhope, which he largely added to, and strongly fortified. Here his mother lived with him until her death, ten years later.