Welsh rebel leader Owain Glyndŵr, having declared himself Prince of Wales, allies himself with the French against King Henry IV of England.

Owain ap Gruffudd Fychan or Owain Glyndŵr was a Welsh nobleman and military commander in the late Middle Ages who led a sixteen-year-long Welsh revolt establishing an independent Wales free from English rule. Owain was acclaimed Prince of Wales by his supporters on 16 September 1400 because of his descent from the rulers of pre-Conquest Wales. Following initial successes, the rebellion was able to take control of the entirety of the country between 1404 and 1405. However, an increase of English military pressure and the lack of foreign aid resulted in the loss of all rebel territory by 1409, after which Owain continued sporadic resistance until his disappearance from the historical record in 1412.