By 1314, Bruce had recaptured most of the castles in Scotland held by the English and was sending raiding parties into northern England as far as Carlisle. In response, Edward II planned a major military campaign with the support of Lancaster and the barons, mustering a large army of between 15,000 and 20,000 men. In the spring of 1314, Edward Bruce laid siege to Stirling Castle, a key fortification in Scotland whose governor, Philip de Mowbray, agreed to surrender if not relieved before 24 June 1314. In March, James Douglas captured Roxburgh, and Randolph captured Edinburgh Castle, while in May, Bruce again raided England and subdued the Isle of Man. News of the agreement regarding Stirling Castle reached the English king in late May, and he decided to speed his march north from Berwick to relieve the castle. Robert, with between 5,500 and 6,500 troops, predominantly spearmen, prepared to prevent Edward's forces from reaching Stirling.