THOMAS, duke of Clarence (c. 1388-1421), who was nominally lieutenant of Ireland from 1401-13, and was in command of the English fleet in 1405, acted in opposition to his elder brother, afterwards King Henry V., and the Beauforts during the latter part of the reign of Henry IV.; and was for a short time at the head of the government, leading an unsuccessful expedition into France in 1412. But when Henry V. became king in 1413 no seri ous dissensions took place between the brothers, and as a member of the royal council Clarence took part in the preparations for the French war. He was with the English king at Harfleur, but not at Agincourt, and shared in the expedition of 1417 into Normandy, during which he led the assault on Caen. On Henry's return to England in 1421, the duke remained in France as his lieutenant, and was killed at Beauge whilst rashly attacking the French and their Scottish allies on March 22, 1421. He left no legitimate issue, and the title again became extinct.