King of Castile and León (1369–1379) and founder of the Trastámara dynasty, who seized the throne by killing his half-brother Peter of Castile.
Henry II of Castile, known as Henry of Trastámara, was king of Castile and León from 1369 to 1379 and the founder of the Trastámara dynasty that would rule Castile for over a century. An illegitimate son of Alfonso XI, he led a long rebellion against his legitimate half-brother Peter of Castile.
Backed by France and the captain Bertrand du Guesclin, he defeated and personally killed Peter at Montiel in 1369, seizing the throne. He is remembered as "the Fratricidal" for that act and as "el de las Mercedes" for the lavish grants of land and privilege with which he bought noble support for his new dynasty.
Henry was born in 1334, one of the many sons of Alfonso XI of Castile by his mistress Leonor de Guzmán. Raised as Count of Trastámara, he grew up in the shadow of his father's open favour toward this second family, and of the hostility of the legitimate heir, Peter. When Alfonso died in 1350 and Leonor was soon executed on Peter's side, Henry became the natural leader of the aggrieved half-brothers.
Henry is a difficult figure to judge fairly, because the dominant chronicle tradition — that of Pero López de Ayala, who served him — was written to justify his usurpation. That tradition presents a capable, politically shrewd, and pragmatic leader whose seizure of the throne, however violent, restored order after Peter's tyranny.
What the record shows plainly is a ruler of ruthless political calculation. He murdered his own half-brother to take the crown, and then secured it by buying the loyalty of the Castilian nobility with enormous grants of land and rights — the "Mercedes Enriqueñas" — that permanently strengthened the aristocracy at the crown's expense. He appears as a usurper who understood exactly what his precarious new dynasty needed to survive.
Having killed Peter at Montiel in 1369, Henry ruled for a decade as the first Trastámara king. His central problem was legitimacy: as an illegitimate usurper he needed to bind the nobility and the towns to his cause, and he did so through the lavish "Mercedes Enriqueñas", grants that made the great noble houses rich and powerful supporters of his line.
In foreign affairs he maintained the French alliance that had won him the throne, keeping Castile a partner of France against England in the Hundred Years' War. He defended his crown against the counter-claims of Peter's daughters and their foreign husbands, above all John of Gaunt, a threat his son John I would finally have to resolve.
Henry II died on 29 May 1379 after a ten-year reign, leaving a consolidated dynasty to his son John I. Later tradition suspected he had been poisoned, but the circumstances are uncertain.
Henry II founded the Trastámara dynasty, which ruled Castile until the union with Aragon and produced Isabella I and the Catholic Monarchs. His grants to the nobility reshaped Castilian politics for generations, entrenching an aristocracy that later kings — including his own descendants — struggled to control. He is remembered as both the fratricide who usurped a throne and the founder of Castile's most consequential royal house.