Alfonso XI was the King of Castile and León from 1312 until his death in 1350. He was born on August 2, 1311, and became king at a young age after the death of his father, Henry II of Castile. Alfonso is known for his military campaigns against the Moors in the Iberian Peninsula, which aimed to expand Christian territories. During his reign, Alfonso XI implemented significant administrative reforms and promoted the development of cities. He is also recognized for his efforts to strengthen the royal authority and improve the legal system. His reign ended with his death during the Black Death pandemic.