Bertrand Du Guesclin, constable of France, born near Rennes, Brittany, about 1314, died near Chateauneuf de Randon, Languedoc, July 13, 1380. He belonged to an ancient family, and though dull at his studies excelled in all sports and manly exercises. In the tournament given at Rennes in 1338 in honor of the marriage of Charles de Blois with Jeanne de Penthievre, he unseated the best knights of Brittany, and bore away the great prize. In the war between the rival claimants of the dukedom of Brittany, the count of Blois and Jean de Montfort, he joined the former, and put himself at the head of a band of adventurers. After the defeat and capture of Charles he was one of the Breton noblemen who went to England to treat for his release. After the battle of Poitiers in 1356, Rennes being besieged by the duke of Lancaster, Du Guesclin forced his way into the place with a few followers, and defended it till the siege was raised in June, 1357. Charles de Blois gave him in recompense the lordship of La Roche d'Airien. Charles V. sent him with a body of troops against the combined forces of England and Navarre, over which he gained a great victory at Cocherel, on the banks of the Eure, in May, 1364. For this he was made count of Longue-ville and marshal of Normandy. In the latter part of this year, however, he was defeated and taken prisoner by Sir John Chandos at Auray in Brittany. Peace being concluded with England, Du Guesclin's companies began to plunder the richest provinces of France; and to rid the kingdom of them Charles procured the release of their leader at a ransom of 100,000 crowns.

Du Guesclin persuaded them to follow him in a crusade against the Moors of Spain, although his real object was to aid Henry of Trastamare in his struggle with his brother Pedro the Cruel for the throne of Castile. On their way southward they levied 100,000 francs upon the pope at Avignon, besides exacting from him absolution and his blessing. They found little difficulty in establishing Henry upon the throne, but Don Pedro having secured the alliance of England, they were defeated by the Black Prince, and Du Guesclin was captured (1367). The conqueror, hearing it rumored that he feared to release his captive, offered to ransom him for 100 francs or less if he chose. Du Guesclin declared that he was worth 100,000 gold florins, and that if the kings of France and Castile would not ransom him there was not a woman in the kingdom who would not contribute to the sum. On his release he again joined Henry, whom he firmly placed on the throne, after defeating Don Pedro. He was created constable of France in 1370, and for several years was employed in the west and south against the English, regaining many places long occupied by them.

The duke of Brittany, fancying himself threatened by Charles, sought the alliance of England, whereupon Charles invaded the province and declared its annexation to France. In consequence of this Du Guesclin resigned his office, and departed for the court of Castile. He paused before Randon, which was besieged by a French army under Marshal Sancerre, and there sickened and died the day before the capitulation. The commander of the garrison, marching out at the head of his troops, placed the keys of the fortress upon the dead body of the hero, who was finally buried in the chapel of St. Denis, by the side of the kings of France. Biographies of Du Guesclin are numerous. Among the more recent are those of Bouille, Histoire de Bertrand du Guesclin (Paris, 1837; Tours, 1843), Fallet (Rouen, 1856-'63), Berard (Dinan, 1862), and Jamison (London, 1864).