The Scottish conflict flared up once again in 1306, when Robert the Bruce killed his rival John Comyn and declared himself the King of the Scots. Edward I mobilised a fresh army, but decided that this time his son would be formally in charge of the expedition. Prince Edward was made the Duke of Aquitaine and then, along with many other young men, he was knighted in a lavish ceremony at Westminster Abbey called the Feast of the Swans. Amid a huge feast in the neighbouring hall, reminiscent of Arthurian legends and crusading events, the assembly took a collective oath to defeat Bruce. It is unclear what role Prince Edward's forces played in the campaign that summer, which, under the orders of Edward I, saw a punitive, brutal retaliation against Bruce's faction in Scotland. Edward returned to England in September, where diplomatic negotiations to finalise a date for his wedding to Isabella continued.