Philip Mowbray John Barbour's "The Brus": He subsequently was made Governor of Stirling Castle which was held by English forces. It came under prolonged siege from Edward Bruce, the King's younger brother, and in 1314 they made a deal that the castle would return to Scottish control unless received by English forces before 24 June. When the English army arrived Mowbray advised Edward II of England against taking Bruce on, but Edward insisted leading to the Battle of Bannockburn. Mowbray subsequently changed to supporting Bruce, and was killed alongside Edward Bruce at the Battle of Faughart in 1318. His brother was Roger
Robert the Bruce 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 capitulate 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