John de Mowbray, 3rd Duke of Norfolk

John Mowbray, 3rd Duke of Norfolk, KG, Earl Marshal was a fifteenth-century English magnate who, despite having a relatively short political career, played a significant role in the early years of the Wars of the Roses. Mowbray was born in 1415, the only son and heir of John de Mowbray, 2nd Duke of Norfolk, and Katherine Neville. He inherited his titles upon his father's death in 1432. As a minor he became a ward of King Henry VI and was placed under the protection of Humphrey, Duke of Gloucester, alongside whom Mowbray would later campaign in France. He seems to have had an unruly and rebellious youth. Although the details of his misconducts are unknown, they were severe enough for the King to place strictures upon him and separate him from his followers. Mowbray's early career was spent in the military, where he held the wartime office of Earl Marshal. Later he led the defence of England's possessions in Normandy during the Hundred Years' War. He fought in Calais in 1436, and during 1437–38 served as warden of the east march on the Anglo-Scottish border, before returning to Calais.