22 June 1402:   Owain Glyn Dwr routs English forces at the battle of Bryn Glas.

After what looked like an abortive uprising in the autumn of 1400, the Welsh revolt under Owain Glyn Dwr revived following the dramatic capture of Conway Castle in April 1401. Through the summer and autumn of 1401 the revolt had blazed into a true national uprising throughout Wales, and by the end of the year the English hold on Wales was vanishing.

The comet that lit the winter skies over Wales in early 1402 seemed to augur well for Owain Glyn Dwr. Back then everyone knew that the appearance of a comet often presaged the birth or rise of a great ruler. Owain seemed to fit the description: he was after all the first true native Prince of Wales to claim the nation’s sovereignty in over a century since the death of Llywelyn the Last in 1282.

But a comet — interpreted as a flaming sword in the sky — could also presage war and devastation. Viewing the same comet from his palace in London, England’s King Henry IV anxiously prepared a campaign against the Welsh for the spring. He knew that Welsh students in England were packing up to go home and join the revolt, and even that some Franciscan monks were channeling funds to Glyn Dwr. Moreover, news from Paris indicated that a pro-Welsh faction at the French court was preparing to lend the Welsh substantial foreign aid, and the appearance of a character in Edinburgh claiming to be the deposed King Richard II meant that the Scottish King Robert might be willing to fish in Henry’s troubled waters. It was imperative that Henry do whatever was necessary to shut down the Welsh rebellion.

In June he sent Sir Edward Mortimer with an army of 8000 men into Wales, a substantial force in those days. But Owain, by now in secure command of much of south and central Wales, quickly gathered his own forces to check Mortimer’s invasion. On 22 June the two collided on a Welsh hillside named Bryn Glas, in mid-Wales just inside the border near Pilleth.

At this battle Glyn Dwr’s smaller force unleased its national “secret weapon”, the Welsh longbow. Properly deployed by trained men, the longbow could be a devastating weapon. Shooting 37-inch long “clothyard” arrows tipped with a specially designed “bodkin point”, the longbow could generate enough force to pierce a knight’s armor. With their arrows handily stuck into the ground in front of them (a practice that incidentially guaranteed a nasty bacterial infection to those wounded by them), the bowmen could wreak fearsome damage on an attacking force before the knights on their heavy warhorses could close in on them.

Not understanding what they were up against, the English knights blundered into an uphill charge against the Welsh, and were slaughtered. Things were made even worse when in the midst of the battle a contingent of Welsh bowmen conscripted to serve with Mortimer suddenly switched sides and sent volleys of arrows into the backs of the advancing English. An appallingly bloody battle by medieval standards, Bryn Glas would be the most lopsided victory won by the Welsh in the course of the war. (Bones from the mass graves on the battlefield were still being plowed up in the 1800s.)

But the real “bombshell”, so to speak, came in the aftermath of the battle when the captured Sir Edward Mortimer married one of Glyn Dwr’s daughters and threw his weight (and considerable political influence) onto the Welsh side. With the English strategy sunk in the shambles of Bryn Glas, the French moved to support the Welsh, assuring that the war would continue, with a victorious and independent Wales now a distinct possibility.

Additional episodes from the revolt of Owain Glyn Dwr and the Welsh War of Independence will be covered in future installments of This Month in Celtic History.