Mortimer, Sir Edmund de definition of Mortimer, Sir Edmund de in the Free Online Encyclopedia.

Mortimer, Sir Edmund de, 1376–1409, English nobleman; youngest son of Edmund de Mortimer, 3d earl of March. In 1398 when young Edmund, the 5th earl, nephew of Sir Edmund, succeeded to the title while still a minor, Sir Edmund became the most powerful representative of his family. He supported the usurpation of the throne by the Lancastrian Henry IV Henry IV, 1367–1413, king of England (1399–1413), eldest son of John of Gaunt and grandson of Edward III; called Henry of Bolingbroke. He founded the Lancastrian dynasty.
..... Click the link for more information. in 1399. In 1402, however, Mortimer was captured by the rebellious Welshman Owen Glendower Owen Glendower (glĕn`dou'ər, glĕndou`ər), Welsh Owain Glyndwr, 1359?–1416?, Welsh national leader.
..... Click the link for more information. , and when the suspicious king forbade his ransom, Edmund entered an alliance with Glendower and married his daughter. Supporting the claim of his young nephew to the throne, he and Glendower continued to fight even after the defeat of their allies, the Percy family (see Percy, Sir Henry Percy, Sir Henry, 1366–1403, English nobleman, called Hotspur or Henry Hotspur; son of Henry Percy, 1st earl of Northumberland . In 1388 he participated in the famous battle of Otterburn, or Chevy Chase, against the Scots; he was captured but later ransomed,
..... Click the link for more information. and Northumberland, Henry Percy, 1st earl of Northumberland, Henry Percy, 1st earl of, 1342–1408, English nobleman. He fought in France in the Hundred Years War, became warden of the Scottish Marches, and was a supporter of John Wyclif .
..... Click the link for more information. ). However, Glendower began to suffer defeats, Mortimer's own effectiveness declined, and he died when besieged by royal forces at Harlech.