At first Glyn Dwr seemed almost as threatening as ever. That winter the men of Pembrokeshire bought a truce with him. But Welsh hopes of further significant assistance from the French were fading. Many French knights, disillusioned by their experience of campaigning in a country where booty and opportunities for glory were limited, returned home before winter. Left behind were 1,200 infantry and 500 crossbowmen under a Picardian commander, Le Beguede de Belay. They apparently spent the winter in comfortable lodgings, and in the spring of 1406 went home before Lent, being badly mauled en route by English ships.
For Glyn Dwr, French support had proved a bitter disappointment. Even his recognition of the French-sponsored Avignon Pope Benedict and plans for a new Welsh Church and two universities were no more than pipe dreams.
The Earl of Northumberland and Lord Bardolph – by no means certain that one of the contending factions in Scotland would not hand them over to the English – headed early in 1406 to Wales. Here they seem to have attempted, without much success, to recruit English malcontents, and by the early summer had left for France.
On 19 February 1406, Prince Henry was made Lieutenant of all Wales and the Marches, providing unified command of the English forces there. He was promised a mobile force of 100 men-at-arms and 3,000 archers, suggesting that it had been decided that the latter more lightly armed mounted troops were better suited for the kind of warfare experienced in Wales than more heavily armoured men.
The tide had clearly begun to turn. In November, Anglesey submitted to the king, with 2,112 of its men seeking terms. Those who remained recalcitrant were outlawed. Glamorgan and Monmouthshire were also steadily passing back under English control. The English recovery was slow, and not without reverses. But eventually it would prove inexorable. The foundations of recovery were the castles, sea power, supply, and, above all, money.
After the king’s expedition of 1405 there would be no more major efforts in Wales. Instead the key to recovery would be the castle. Lack of finance had been the major obstacle to the effectiveness of this strategy in previous years. In 1404 the royal council had calculated that the daily cost of maintaining fourteen castles with garrisons totalling 1,415 men would be the alarming sum of £42 (around £2,000 in present-day terms). But the English also had technological advantages in the ‘castle war’. The Welsh were rarely in possession of adequate siege equipment, while the English, when they were able to commence operations to regain the lost castles, could deploy the full panoply of siege engines, cannon and other equipment. Sea power also enabled the English – albeit it with difficulty – to maintain control of other coastal fortresses, although several seem to have fallen briefly into Welsh hands. It was bad weather, and spasmodic French naval presence, that had led to Glyn Dwr’s capture of Harlech and Aberystwyth.
In July 1406 English ships based at Chester landed troops in Anglesey to begin the recovery of that fertile part of North Wales, important in feeding the rebels. It was probably English sea power that also thwarted any Welsh counter-attack across the Menai Straits. It is noticeable, however, just how long it had taken the English authorities to adopt the methodical process of conquest and occupation that had been a feature of the successful operations of Edward I a century earlier. Coupled with offensive measures was a substantial campaign to starve the Welsh of supplies and munitions. The rebellion, given the limited Welsh resources, could never be entirely self-sustaining. Although perhaps lacking other results, King Henry’s chevauchées at least pointed out the relevance of a ‘scorched earth’ strategy. Although it was never possible completely to stifle illegal trade with the Welsh by English merchants, the restrictions that were imposed forced much of Welsh strategy to revolve around raiding across the border in order to obtain supplies. In the end, a shortage of essential foodstuffs, coupled with the ferociously hard winter of 1407-1408 did much to hasten the collapse of the rebellion.
Glyn Dwr was aided by the somewhat chaotic system of administration represented by the Marcher lordships, which hindered any coherent English strategy, and still more by the financial and political challenges facing King Henry until at least 1406. Historically, Wales had always prospered when the government of its mighty English neighbour was weak, and this was never more the case than during much of the Glyn Dwr rebellion. An already hard-pressed exchequer, faced by threats from Scotland and France, was even more straitened by the loss of its Welsh revenues, which could, in theory, amount to £12,000-14,000 out of an annual total of £75,000-90,000. The annual maintenance costs of just five castles in North Wales came to £5,561 (over £233,000 in present-day terms).
Lack of English funds did much to prolong the war. During its early years, commanders from Prince Henry down repeatedly complained of a shortage of money. It was not until the financial situation began to improve that a more coherent military strategy became apparent, and the tide of the rebellion began to ease. At the same time English forces began to go over to the offensive, rather than merely attempting to contain the rebels. An attempted Welsh offensive in the spring of 1406 seems to have met with at least two serious reverses, one of them, in the Mortimer territory of Powys, reportedly involving Northumberland and Bardolph. These setbacks certainly hastened the submission of South East and parts of North East Wales by the end of the year. Much of Ceredigion and probably the Twyi valley also submitted.
And so, by the start of 1407, Glyn Dwr was being steadily pushed back. Northern Powys submitted by July and the Lordship of Denbigh in North Wales in September. Tiny detached Maelor Saesnig surrendered in May. The only parts of Wales under Glyn Dwr’s firm control were Caernarvonshire, Merionethshire and northern Ceredigion. Even here English power was resurgent. In May, Prince Henry was appointed to serve in Wales for six months with 600 men-at-arms and 1,800 archers. In North Wales Gilbert Talbot with 100 men-at-arms and 400 archers was sent to collect fines in Caernarvonshire and Merioneth.
But the main English effort of the summer was intended to be the recapture of Aberystwyth Castle. This was meant to be a great symbolic English triumph and Prince Henry, the somewhat unreliable Duke of York and the Earl of Warwick, were among the many notables who gathered for the kill. Siege guns and engines were brought up and supplies ferried in by sea. Eight guns – probably those earlier employed in the north against the Percy castles – were to be taken from Pontefract to Bristol by land and thence transported by sea to Aberystwyth. Provisions and supplies of all kinds were also prepared. Timber (for siege engines and ladders) was to be cut in the Forest of Dean, then transported to the siege in two barges.
The original intention had been for the king to take personal charge of operations, but possibly because of concerns about simmering unrest in the north, Prince Henry was left in command in Wales. The Admiral, Thomas, Lord Berkeley, took day-to-day command of operations at Aberystwyth, and the king’s 4½-ton gun, ‘Messenger’ was sent from Nottingham to intensify the bombardment, with additional powder and ingredients for its manufacture.
But one gun burst during firing, while the slow progress of the siege seems to have sapped confidence of a quick and decisive conclusion among the English nobility. The Welsh garrison, under Rhys Ddu, was running short of provisions by late September and on the 12th they invited twelve of the English leaders into the castle for discussions. It was agreed that Aberystwyth and its garrison would be surrendered if not relieved by the week ending 1 November, and hostages were exchanged in an armistice that would be observed in the interim. The garrison was to be pardoned once the surrender took place. Leaving behind 120 men-at-arms and 360 archers in garrison at Ystrad Florida Abbey, Prince Henry returned to Hereford. The king, feeling that the surrender of Aberystwyth would signal the effective end of the rebellion, planned to be present in person.
But, as so often, his hopes were dashed. Before the agreed surrender date, Glyn Dwr managed to enter the castle in secret and repudiated the agreement, condemning those who had made it as traitors. The English troops were deserting, and once again rumours were circulating regarding the loyalty of the Duke of York, although Prince Henry declared that it was only the duke’s efforts that had saved the expedition from disaster.