English Longbowmen (many were actually Welsh) represented the machine-guns and repeating- rifles of today's warfare. Their famed yew long-bows were feared with good reason: they could stand well back from the enemy and shower them with arrows. An archer with a 2m longbow could hit a target at up to 250m, downing the enemy ranks at virtually no risk to themselves.
Roughly one third of the English infantry at Bannockburn were Archers but a mixture of difficult terrain, closer than expected combat and bad judgement combined to cancel out the devastating effectiveness anticipated by both sides.
By the time the Archers were finally deployed on the second day of battle, things were already going badly for the English.
At a pivotal point in the battle, Bruce anticipated the flanking position of gathering archers and dispatched Sir Robert Keith and his Scottish cavalry to deal with the threat. Robert Keith was the hereditary Marshal of Scotland, a ceremonial role that once involved looking after the King's horses. By Bannockburn, however, he was a feared adversary; he and his small but finely-honed cavalry reached the archers as they were drawing into formation and routed them before the threat could be realised.
That was the last that was heard of the mighty longbow on the fields of Bannockburn.