The English soldier-statesman John of Gaunt (1340-1399), 5th Duke of Lancaster, played an active part in military and political affairs.
Born in March 1340, John of Gaunt was the fourth son of Edward III and received his name from his birthplace, Ghent. He was created Earl of Richmond in September 1342. Trained in military skills, at the age of 19 he took part in an expedition to France, and on May 19, 1359, he married Blanche, younger daughter and coheiress of Henry of Lancaster. Through this marriage he was created Earl of Derby in April 1362 and in November Duke of Lancaster.
For the next years Lancaster was active in various military campaigns, serving under his brother Edward the Black Prince in Spain in 1367, as captain of Calais 2 years later, and in 1371 as lieutenant of Aquitaine. After the death of his first wife in September 1369, he married Constance of Castile in 1372, surrendered his title of Earl of Richmond, and assumed the title of king of Castile.
Upon his return to England Lancaster took an active part in politics as head of the court party that was opposed by the "Good Parliament" of 1376. At the same time he supported John Wyclif and protected him from the Londoners at the Council of London the following year. With the accession of Richard II in 1377, Lancaster had great influence at court, advising on the French war, serving on the Scottish border and making a truce there in 1380, and serving on several commissions the following year to deal with the rebellion of 1381 and the reform of the royal household.
Lancaster continued to serve Richard II in other roles: negotiating peace with France and dealing with the Scottish border. But in 1385 he fought with the King and, though reconciled, continued to serve as a mediator between the King and his opponents. In 1388 he was made lieutenant of Guienne and in 1390 Duke of Aquitaine, but he failed to have the latter claim recognized. After he married his daughter Catherine to Henry of Castile, he gave up the claims to the kingship of that country, and after effecting a reconciliation between the Duke of Gloucester and Richard, Lancaster retired from active politics. With the death of his second wife, in 1396 he married Catherine Swynford. He died in early February, 1399.
After Lancaster's death Richard seized his estates, which caused Lancaster's son, Henry of Bolingbroke, to claim the throne as Henry IV. The children of his last marriage, known as the Beauforts by patent in 1397, were the line through which Henry Tudor (Henry VII) claimed the throne.
The standard biography of John of Gaunt is Sydney Armitage-Smith, John of Gaunt (1905; repr. 1964). Information on the period can be found in Sir James H. Ramsay, Genesis of Lancaster (1913), and May McKisack, The Fourteenth Century (1959).