Scotland in the Middle Ages excommunication of Bruce and his followers by Pope Clement V, his support slowly strengthened; and by 1314 with the help of leading nobles such as Sir James Douglas and Thomas Randolph only the castles at Bothwell and Stirling remained under English control. Edward I had died in 1307. His heir Edward II moved an army north to break the siege of Stirling Castle and reassert control. Robert defeated that army at the Battle of Bannockburn in 1314, securing "de facto" independence. In 1320 the Declaration of Arbroath, a remonstrance to the pope from the nobles of Scotland, helped convince Pope
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