The Scots, following an agreement made between the nobility at Aberdeen, mustered at Jedburgh in August, including the levies of the earls of Fife, March, Moray and those of Archibald the Grim. Upon finding from an English spy, that the English warden Percy was aware of the muster, and was planning a counter strike, the Scots command decided to split the army, with Fife leading the main body into Cumberland, while a smaller mounted force under Douglas was to go east and despoil Northumberland.