John de Mowbray, 2nd Duke of Norfolk, 3rd Earl of Nottingham, 8th Baron Mowbray, 9th Baron Segrave KG, Earl Marshal (139219 October 1432) was an English nobleman and soldier. He was a younger son of the first Duke of Norfolk and Lady Elizabeth Fitzalan, but inherited his father's earldom of Norfolk (but not the dukedom) when his elder brother rebelled against King Henry IV and was executed before reaching the age of inheritance. This and the fact that his mother lived to old age and held a third of his estates in dower, meant that until the last few years of his life he was, although an important political figure, poorly-off financially. Probably due to the need to augment his income, he took the still-popular path for young members of the English nobility by taking part in the Hundred Years' War in France. His first campaign was in 1415 with Henry V, and although he took part in some of the great expeditions, he, like so many of his comrades, fell badly ill with dysentery and had to return to England. For this reason, he missed the Battle of Agincourt. When Henry V died in 1422, Mowbray remained a leading commander of the armed forces in France for the new boy-king, Henry VI. He continued campaigning there for the next five years, and, when parliament decided it was time to crown the new young king—in both Westminster Abbey and in France—Mowbray acted as both royal bodyguard and councillor. He also took part in Humphrey, Duke of Gloucester's personal campaign in Hainaut, which appears for once to have been profitable to him. Foreign service occupied most of Mowbray's career but often cost him more than he gained from any spoils. Hence it was not until his mother died in 1425 that his fortunes changed for the better; not only did he inherit her large share of his father's estates, but he also received promotion from Earl of Norfolk to Duke of Norfolk. This followed a bitter dispute, while he was still earl, with Richard Beauchamp, Earl of Warwick, as to who held precedence within the English peerage; the question was never resolved, but avoided by making Mowbray a duke. Whilst still a youth Mowbray had been married by his guardian, Ralph Neville, 1st Earl of Westmorland, to Neville's eldest daughter, Katherine; Mowbray's marriage had cost Westmorland the princely sum of £2,000.