The military importance of Wales and its March changed markedly between the late thirteenth century and the early years of the fifteenth century. Welsh soldiers served every English king in this period but did so in ways that followed the needs of England. Contrary to myth, the Welsh archers in Henry V's army did not win the battle of Agincourt for him and it was rare that Welsh soldiers performed truly notable service. Welshmen feature only occasionally in chronicle accounts of warfare in the period and, of the great battles of the Hundred Years War, it was only at Crécy that their role was noted directly. In truth, by 1346, the ‘golden age’ of the Welsh soldier had passed. In Edward I's reign, the ability of the English Crown to raise enormous armies of Welshmen from the newly conquered lands in Wales was transformative.

Edward I's great military achievement was the integration of the men of the lands of Wales into the English war machine he and his officials had created to fight them. In truth this task was made easier by the nature of the Welsh wars. These were primarily conflicts between Welshmen in which the English became involved. As a result, members of the Welsh elite were familiar with the English court through diplomatic missions, as hostages or as exiles. Welsh warriors had guided and fought alongside English forces. As overlord of all the shires and March of Wales after 1282, Edward seems to have met only occasional resistance to recruiting from the Marcher lordships in his arrays of men. On occasions the lords of the March allowed royal officials to supervise their tenants when they served as soldiers, but this co-operation as not to be taken for granted.

Edward I's ‘infantry revolution’, in which the king of England was able to routinely raise and sustain armies over 10,000 men, would not have been possible without the resources of the men of Wales that the conquest of Gwynedd provided. While he would not have been able to raise infantry armies of the scale he fielded at Falkirk without 10,000 Welshmen, it should be remembered that just as many Englishmen served in Edward's infantry as Welsh, albeit drawn from a much larger population.