Enraged by the killing of John Comyn, Lord of Badenoch by Bruce and his followers at Dumfries and Bruce’s coronation Edward I of England named Aymer de Valence, Earl of Pembroke, special lieutenant for Scotland. Pembroke moved quickly, and by the middle of summer he had made his base at Perth, along with Henry Percy and Robert Clifford and an army of about 3000 men drawn from the northern counties. Edward I gave orders that no mercy was to be granted and all taken in arms were to be executed without trial.

It is possible that this word had not reached the king because he resorted to a chivalric tradition and called on de Valence to come out from the walls of Perth and do battle. De Valence, who had the reputation of an honorable man, made the excuse that it was too late in the day to do battle and said he would accept the challenge on the following day. The king bivouacked his army some six miles away in some woods that were on high ground near the River Almond. At about dusk as the Bruce's army made camp and many disarmed, the army of Aymer de Valence fell upon them in a surprise attack.

The king unhorsed the Earl of Pembroke in the first onslaught but was unhorsed himself and nearly captured by Sir Philip Mowbray only to be saved by Sir Christopher Seton. Outnumbered and taken by surprise, the king's force had no chance. Bruce was twice more unhorsed and twice more rescued. At the last, a small force of Scottish knights including James Douglas, Neil Campbell, Edward Bruce, John de Strathbogie, Earl of Atholl, Gilbert de Haye and the king formed a phalanx to break free and were forced to flee in a shattering defeat, leaving many of the king's most loyal followers dead or soon to be executed. After being defeated at the battle, the king was driven from the Scottish mainland as an outlaw.