The year 1404 saw Glyn Dwr at the height of his power. Although in March, in an attempt to draw a line under the Percy rebellion of the previous summer, the king granted a general pardon to all involved in acts of rebellion in the Welsh Marches and the north during the previous year, rumours of the imminent return of King Richard continued. And Henry remained crippled by lack of money, and facing threats of French attacks by sea.
Although the assault on Caernarvon in November had failed, the French and the Welsh insurgents had not abandoned their efforts there. The garrison in the summer of 1403 had totalled twenty men-at-arms and eighty archers, but during the course of the year this had dwindled to twenty-eight, including townsmen. For their renewed attack, the Welsh and French built siege engines – a very rare feature in Glyn Dwr’s operations – sows (covered mobile siege towers) and long scaling-ladders. They also evacuated livestock from Anglesey, which was vulnerable to attack from the sea.
On 16 January the siege began, the acting governor of Caernarvon, Robert Parry, sending a woman to Chester in a plea for help.
Caernarvon was not the only garrison under threat. Two more links in Edward I’s ‘stone ring’ around Snowdonia, Harlech and Aberystwyth, were also in danger. During the autumn of 1403 the garrison of Harlech had arrested their constable, William Hunt, on suspicion he was about to surrender the castle to the Welsh. However, the strength of the garrison dwindled, some dying as the result of sickness, others deserting, while a few were killed attempting to run the Welsh gauntlet and reach Chester. Early in January an attempt to reach a truce with the Welsh failed and three more of the original garrison of ten men-at-arms and thirty archers were captured. By now the defenders consisted of five Englishmen and a few townsmen.
The relief of the threatened coastal castles was supposed to be the responsibility of Lord Berkeley, Admiral for the South and West, but although he had been provided with £2,344 to pay for supplies and men, he proved, perhaps because of winter weather, unable to achieve much.
All of the coastal fortresses from Caernarvon to Cardigan remained under close blockade by the Welsh. Harlech, in particular, was doomed and Glyn Dwr made a deal with the remaining garrison that they would surrender if not relieved by a stipulated date.
During the spring, with Prince Henry not yet returned to his command, Welsh raiders – reportedly with French reinforcements – devastated a third of Shropshire up to the gates of Shrewsbury, and there were wild rumours that Glyn Dwr was marching on Northampton.
At the end of March – Parliament having, for the moment, supplied the king with some funds – John Stevens of Bristol was ordered to take five ships laden with salt, corn, vinegar and wine to supply the coastal castles.
Once again, Caernarvon proved too strong for its attackers but at some point in the late spring, Harlech fell to Glyn Dwr.
And the Welsh tide of success was sweeping through South Wales. Despite orders to the Earl of Devon to reinforce it, the town and castle of Cardiff fell to Glyn Dwr, and the town was plundered and burnt. Caerphilly, Usk, Caerleon and Newport Castles fell, or were abandoned by their garrisons. Most of the countryside was in rebel hands, and the body of one of the Welsh members of Caernarvon’s garrison had to be taken by sea for burial at his home in the Lleyn Peninsula, as the town was completely isolated by land.
Possibly inflated estimates credited Glyn Dwr with a potential army of 30,000 men, although he would never have been able to supply or maintain such a large force. To many churchmen, of whatever sympathies, Owain was seen as ‘the rod of God’s anger’.
Probably by the start of summer, although in unknown circumstances, Aberystwyth town and castle also fell to the Welsh. Glyn Dwr now effectively controlled most of Wales outside the walls of its remaining English-held towns and castles. It was clearly time for him to move forward from being a successful leader of guerrillas towards trying to establish a more coherent administration in the areas under his control. Indeed, to maintain credibility and impetus, Owain had no real alternative.
By the spring of 1404, Glyn Dwr had formally assumed the title ‘Prince of Wales’. This not only represented an end of any possibility of reconciliation with the English government but also made a statement of his intent to establish a Welsh state on an equal footing with European counterparts.
A further testament to the growing credibility of Owain’s cause came with the defection to him of a number of prominent churchmen, who were often experienced administrators. Among them were John Trefor, Bishop of St Asaph, Lewis Byford, Bishop of Bangor, and the brilliant (and illegitimate) Gruffydd Yonge, who became Owain’s chancellor and probable candidate for archbishop of a new, independent Welsh Church.
These men provided Glyn Dwr with the substance as well as the trappings of government. Their first task was to cement the current informal alliance with the French into a more concrete agreement. Yonge and Owain’s brother-in-law, John Hanmer, were despatched to Paris to thrash out the details. With the war party at the French court in the ascendancy, they met with a favourable reception, and in July a formal treaty of friendship was signed between Owain and King Charles VI of France. As well as an undertaking that neither party would seek a separate peace with England, the treaty also promised French military assistance to the Welsh. An expeditionary force of 800 men-at-arms and 300 crossbowmen under the Count of La Marche was assembled in Brittany, although bad weather would prevent it from sailing that year.
Owain was by now informing his supporters that ‘you may know that their [the English] time is ending, and victory is turning to us according to God’s ordering from the first, which none can doubt’. In furtherance of his claims, a Welsh Parliament was summoned that summer to meet at Machynlleth, with four representatives from each commote – the historical Welsh administrative unit, corresponding to the English ‘hundred’.
Throughout the summer, the tide of Welsh success continued to swell. Herefordshire and Shropshire reeled under the impact of Welsh raids, with parts of western Herefordshire, at least, probably effectively under rebel control. Once again, King Henry lacked the money to finance any effective response. He made no effort to mount his annual chevauchée into Wales. Though by the autumn Prince Henry was apparently back in command on the Welsh border, the situation had deteriorated to such an extent that the King’s Council was forced to acquiesce in the men of Shropshire paying the Welsh for a three-month truce.
With most of Wales effectively in Glyn Dwr’s hands, King Henry’s enemies nearer to home were also showing signs of renewed activity. For the Earl of Northumberland, following the death of his son and the desecration of his body, his original grievances with the Lancastrian regime had now assumed the character of the traditional northern ‘blood feud’. By the end of 1404 he was merely awaiting an opportunity to strike. Summons to the earl to attend King Henry were ignored on varying pretexts, until the threat of an accusation of high treason eventually brought Northumberland to a meeting with the king at Pontefract, around Midsummer’s Day. He also handed over for trial and subsequent execution one Richard Searle, one of the impostors who had passed himself off as King Richard. Northumberland also agreed to hand over his remaining northern castles, in return for property of equal value elsewhere.