Duke (Fr. duc, Lat. dux, from ducere, 'to lead'), a term applied originally to any military leader. The title came first into formal use when Constantine separated the civil and the military commands in the provinces. From that time forth, the military governors of provinces were either counts or dukes. But these titles originally stood to each other in an opposite relation to that which they afterwards assumed. 'All provincial generals,' according to Gibbon, 'were dukes, but no more than ten among them were dignified with the rank of counts, or companions, a title of honour, or rather of favour, which had been recently invented in the court of Constantine.' See COUNT. Both were strictly prohibited from interfering in any matter which related to the administration of justice or the revenue. When the Germanic barbarians invaded the provinces of the empire, the military chiefs of their tribes (called by names cognate with heretoga or herzog) were sometimes identified with the duces; but amongst the Franks and Longobards, the functions of the so-called dux were rather those of the old German Graf (Lat. Comes; see COUNT). By-and-by the ordinary count became the lieutenant of the duke, and the government of the latter extended to several provinces; whereas that of the former was confined to one province, or even to a single locality. The power of the dukes grew so rapidly, in consequence of the dissensions of the Merovingians, that, towards the end of the 6th century, they arrogated to themselves the right to dispose of the crown. In the 10th century, the East Frankish empire fell into the five hereditary dukedoms of Franconia, Swabia, Bavaria, Saxony, and Lorraine. In the west, the dukes of the Isle of France, Aquitaine, Burgundy, Normandy, Gascony, and others assumed the crown and sceptre, promulgated laws for their subjects, struck money with their own image, and made war in their own name against the crown. The confederation of the feudal lords had assumed such dimensions, that about the period of the Norman invasion of England nothing remained directly under the crown except a few towns, of which Rheims and Laon were the chief. The rest of the kingdom was divided amongst the dukes and the counts, under an obligation, which they almost always evaded, of service and fidelity to the crown. But by 1514 these regal duchies had been either extinguished or reunited to the crown.
The duchies which were granted to members of the royal family—that of Bourbon, erected in 1327; of Orleans, in 1344; of Auvergne, Berri, Touraine, Valois, and Alençon at later periods—enjoyed none of the privileges of independent sovereignty which had belonged to the ancient duchies; and when the Montmorencies were created dukes in 1551, they enjoyed no other privileges than those of titled nobles. The duke-peers, as they were called, were simply the first class of nobles in France, just as dukes are in England. Several prelates enjoyed this rank—as, for example, the Archbishop-duke of Rheims. There were also in France dukes for life, or patent dukes, who dated only from the reign of Louis XIV. Swept away by the Revolution, the title was restored by Napoleon, who conferred it, with rich endowments, on his marshals. Several ducal peers were created by Louis XVIII. and Charles X. In Germany, the dukedom passed through phases very similar to those which it exhibited in the earlier history of France. The title of grand-duke was first bestowed on Cosmo de Media, Grand-duke of Tuscany, by Pope Pius V. in 1569; it is assumed by the princes of the imperial family of Russia, and also adopted by certain German reigning princes. Archduke (q.v.) is Austrian only.
William the Conqueror, Duke of Normandy, may be held to have brought the title as a separate dignity into England; but it was merged in the crown until the reign of Edward III., who, in 1337, conferred the dukedom of Cornwall on the Black Prince, his eldest son, and in 1351 that of Lancaster on Henry Plantagenet, his cousin. These were dukedoms by tenure, Cornwall (q.v.) being in the one case erected into a duchy, and palatine jurisdiction being in the other conferred within the county of Lancaster. In later cases the dignity of duke was personal, and unaccompanied with grants of lands and annuities. In 1362 Edward III. conferred the dukedom of Clarence on Lionel, his third son, and the dukedom of Lancaster on John of Gaunt, his fourth son and husband of the then heiress of the former Duke of Lancaster. Two other sons of Edward III. were in 1385 made Dukes of York and Gloucester respectively by their nephew Richard II. This king first extended the title beyond the royal house. In 1386 he made his favourite, Robert de Vere, Duke of Ireland, and in 1397 he created five dukes and a duchess in one day—viz. the Dukes of Hereford, Surrey, Exeter, Albemarle, and the Duke and Duchess of Norfolk. The creation of dukes was at that time by patent, there being an inaugural ceremony of girding with the sword in parliament. In the reign of Henry VI., the recipients of dukedoms included Humphrey Stafford, Duke of Buckingham, Henry de Beauchamp, Duke of Warwick, and William de la Pole, Duke of Suffolk. Henry VIII. made his illegitimate son, Henry Fitzroy, Duke of Richmond, and his brother-in-law, Charles Brandon, Duke of Suffolk. Three dukes were created by Edward VI., Edward Seymour (the Protector and king's uncle) being made Duke of Somerset; Henry Grey, Duke of Suffolk; and John Dudley, Duke of Northumberland. Yet on Elizabeth's accession, in consequence of attainders and extinctions, the only remaining duke was Thomas Howard, Duke of Norfolk; and on his execution and attainder, the title of duke was non-existent in England. James I. in 1623 made the Scottish Duke of Lennox Duke of
Richmond, and his favourite, George Villiers, Duke of Buckingham. Charles I. conferred the dukedom of Cumberland on Prince Rupert. Charles II. (q.v.), besides creating General Monk Duke of Albemarle, and the Marquis of Worcester Duke of Beaufort, bestowed the dukedoms of Monmouth, Grafton, Northumberland, and St Albans on four of his natural sons. Under William, Anne, and George I. a number of holders of lower dignities in the peerage were advanced to the rank of duke. From the accession of George II. comparatively few dukedoms have been created, except those conferred on younger members of the royal house. Since the accession of Henry IV., the dukedom of Lancaster has been merged in the crown; there has been no Duke of York since 1827; and the dukedom of Cornwall is held by the heir-apparent. Of the presently existing dukes of England, Great Britain, and the United Kingdom (twenty-two in number, exclusive of princes of the blood-royal), only two, Norfolk and Somerset, date before the Civil War.
The introduction of the title duke into Scotland seems to have arisen out of the claims of precedence made by Henry IV., when Duke of Lancaster, over the Scottish princes, who were merely earls, at international congresses. The first Scottish dukes were made in 1398—viz. David, eldest son of Robert III., who was made Duke of Rothesay; and the king's brother, Robert, Earl of Fife and Men-teith, who was made Duke of Albany (q.v.). The dukedom of Albany (the old name for Scotland) was an empty honour unconnected with lands, and the only instance of a Scottish dukedom that did not possess more or less of a territorial character. David, Duke of Rothesay, died without issue in Falkland Castle, in 1402, and in virtue, it has been assumed, of the original constitution of that dukedom, the title in later times belonged to the heir-apparent of the Scottish crown. Prince Henry, eldest son of James VI., was, at his baptism in the Chapel Royal at Stirling, invested with the dignity of Duke of Rothesay, with appropriate solemnities, including the imposition of a ducal crown. The title of Duke of Ross was given by James III. to his second son, James, who became Archbishop of St Andrews; and the same king, on the eve of the rebellion in which he lost his life, bestowed on his devoted adherent, David, Earl of Crawford, the title of Duke of Montrose. The dukedoms of Ross, conferred on Henry, Lord Darnley; of Orkney, bestowed on the Earl of Bothwell on his marriage with Queen Mary; and of Lennox, given to Esmé Stewart, Earl of Lennox, cousin-german of Darnley, were the only other Scottish creations before the union of the crowns. Hitherto the jealousy of the feudal nobles had been so great an obstacle to the extension of this title beyond the near relations of the royal house, that James, Earl of Arran, though regent of Scotland and next heir to the throne in Queen Mary's minority, had to derive his title of duke (Châtellerault) from France. Ten Scottish dukedoms appear on the Union Roll of 1707, of which Hamilton alone dated before the Civil War. Rothesay, which had been overlooked, was added in 1714. Of these eleven dukedoms, two are extinct, and Queensberry is conjoined with Buccleuch, reducing the present number of dukes in the peerage of Scotland to eight. A duke (except a royal duke) in the peerage of the United Kingdom is styled 'Your Grace' and 'The Most Noble.' His wife is a duchess. For the designation of his sons and daughters, see COURTESY TITLES. His parliamentary robe is of scarlet, with four doublings of ermine. For the form of his coronet, see CORONET.
The translators of the Old Testament introduced the term duke into the English authorised version as an appropriate designation for certain Eastern potentates.