Jean Bureau (c. 1390 – 1463) was a French artillery commander active primarily during the later years of the Hundred Years' War. Along with his brother, Gaspard, he is credited with making French artillery the most effective in the world. As Master Gunner of Artillery in the armies of Charles VII, Bureau acquired a reputation as an effective artillery officer during the Normandy campaign (1449–1450), when his bombardments helped capture the towns of Rouen, Harfleur, and Honfleur, and aided in the French victory at Formigny. Bureau commanded the victorious French army at the decisive Battle of Castillon in 1453. Early life and campaigns Bureau was born in Semoine, Champagne, the second son of Simon Bureau, a merchant, and his wife, Hélène. In 1420, he moved to Paris to work as a lawyer. He was a legal official at the Châtelet during the occupation of Paris by the Duke of Bedford. Described as a "perfectionist with a methodical, mathematical mind" and "an imaginative technician who knew how to get the best out of his primitive weapons", Bureau likely learned the artillery trade for its commercial potential. The Bureau brothers were aided by innovations in the manufacture of gunpowder in the late 1420s that generated a more potent powder that could fire projectiles at a much greater velocity and did not require mixing in the field. Simultaneously, innovations in casting helped create stronger barrels that were less likely to explode. In 1434, the Bureaus offered their services to Charles VII, and quickly asserted themselves as artillery experts. Jean was appointed "governor of the French archers" and Gaspard was appointed "master of ordnance", and by 1439, Jean was the Master Gunner of the French Artillery. Jean was also appointed "Receiver of Paris" in 1436, "Treasurer of France" in 1443, and mayor of La Rochelle in 1448. The Bureaus' artillery had an immediate impact, aiding the French in the sieges of Montereau (1437), Meaux (1439), Saint-Germain-en-Laye (1440), and Pontoise (1441). The Bureaus helped suppress the Praguerie rebellion against Charles in 1440. Later campaigns When the Treaty of Tours (which had established a truce between England and France) ended in 1449, Charles VII launched a campaign to retake Normandy in northern France. Bombardments by the Bureaus' artillery aided in the capture of Rouen (October 1449), Harfleur (December 1449), Honfleur (January 1450), and Fresnoy (January 1450). To ensure a continuous bombardment of English-held Cherbourg, the Bureaus