Henry of Trastámara was a Spanish nobleman born in 1334, known for his role in the Castilian Civil War. He was the son of King Alfonso XI of Castile and Leonor de Guzmán. Henry claimed the throne of Castile, leading to a conflict with his half-brother, Peter of Castile, which resulted in a series of battles for control over the kingdom. In 1366, Henry became King of Castile after defeating Peter, who was later assassinated. His reign was marked by political instability and challenges from rival factions. Henry ruled until his death in 1379, leaving a complex legacy in Spanish history.