King John II of Castile was a monarch who ruled from 1406 to 1454. He was the son of Henry III of Castile and Catherine of Lancaster. His reign was marked by political instability and conflicts with the nobility, which often challenged his authority. John II sought to strengthen the monarchy and reduce the power of the nobles. During his rule, John II also focused on cultural and economic development. He supported the arts and literature, leading to a flourishing of Spanish culture. His reign laid the groundwork for future developments in Castile and the broader Iberian Peninsula.