Of all England's fourteenth-century kings, Edward II was the most dependent upon his Welsh subjects. As the first English prince of Wales he had been lord of the shires of both North and West Wales. Aside from being born in the midst of the building site that was Caernarfon Castle, he had maintained a number of Welshmen in his household as prince. Nevertheless it is likely that the connection with the uchelwyr, the class of the native elite that had deserted Llywelyn ap Gruffudd, was acquired on campaign. The loyalty displayed towards Edward II by this group right until the end of his reign is remarkable and the importance of this support has been underappreciated by many historians. Edward II's military machine was very much the same as that developed by Edward I but was extended above and beyond sustainable levels, and the number of Welshmen employed by Edward II in his campaigns to Scotland was larger even than those deployed by his father in the 1290s. The machine was found wanting most tellingly at Bannockburn in 1314 and again in 1322, but Edward did little to change the nature of his armies and few of his campaigns enjoyed conspicuous success. Enormous levies of Welshmen, generally led by their fellow countrymen, were essential to Edward's ability to wage war and also for the ability of his barons to oppose him. Most of Edward's opponents held substantial Marcher lordships so it was natural that, in their struggles with their king, Edward's barons deployed their Welsh tenants to buttress their causes. In the dispute over the ordinances intended to limit Edward's power in 1312, in the war fought against Hugh Despenser the younger in 1321 and in support of Thomas of Lancaster during the winter of 1321–22, the power of the lords of the March was measured in the numbers of men their estates could supply.

This chapter will consider the role of Welsh military resources in the political narrative of Edward II's early reign before turning its attention to the continuation of the wars against the Scots as far as Bannockburn. Next, it will discuss the political fallout from this cataclysmic defeat as it related to Wales: the revolt in Glamorgan led by Llywelyn Bren in 1316 through to the campaigns that led to the defeat of the king's enemies at Boroughbridge in 1322.