Henry IV (1399-1413), the son of John of Gaunt, duke of Lancaster, seized the English throne at the age of thirty-two from his cousin Richard II and held it until his death, aged forty-five, when he was succeeded by his son, Henry V. This comprehensive and nuanced biography restores to his rightful place a king often overlooked in favor of his illustrious progeny.

Henry faced the usual problems of usurpers: foreign wars, rebellions, and plots, as well as the ambitions and demands of the Lancastrian retainers who had helped him win the throne. By 1406 his rule was broadly...