Clan Sinclair to St Briavels Castle, and in 1296 he swore fealty to Edward I of England. In 1303 the Battle of Roslin took place where Scots under Henry Sinclair of Rosslyn and the Clan Comyn defeated an English force. The Battle of Loudoun Hill took place in 1307 where Scots under Robert the Bruce, assisted by Henry Sinclair of Rosslyn again defeated the English. The family initially favoured John Balliol's claim to the throne but later it became paramount that they gave their loyalty to Robert the Bruce. The Battle of Bannockburn was fought in 1314, where the Clan Sinclair fought
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