Owain Glyndwr

Following a dispute with English lord Reginald Grey, Owain Glynd

Glyndŵr's forces defeated an English army led by Sir Edmund Mortimer at Bryn Glas in Powys. Mortimer was captured and later allied with Glyndŵr through marriage. The victory boosted the rebellion's momentum and secured control over much of Wales.

Glyndŵr convened a Welsh parliament at Machynlleth, where he was crowned Prince of Wales. He established diplomatic relations with France and Scotland, and outlined plans for an independent Welsh church and university. This represented the peak of his rebellion's political organization.

Glyndŵr signed the Treaty of Paris with France, securing French military support against England. A French expeditionary force landed in Wales and joined the rebellion. The alliance temporarily strengthened the Welsh cause but failed to achieve decisive victory.

English forces under Prince Henry (future Henry V) recaptured Harlech Castle, Glynd