Alfonso, Prince of Asturias (1453–1468)

:"For other Princes of Asturias named Alfonso, see Alfonso, Prince of Asturias"

Infante don Alfonso de Trastamara y Aviz, Prince of Asturias (1453–1468) was the figurehead of rebelling magnates against his brother Henry IV of Castile.

Alfonso was the only surviving son of John II of Castile, by his second wife Queen Isabel de Portugal, Henry IV being the product of his first marriage. Alfonso's sister, the future Queen Isabella I of Castile, was also the product of this second marriage.

Childhood

After the death of his father, John II, Alfonso, his mother and sister were virtually exiled, his mother to Arevalo and the children to Segovia. When Alfonso was around seven years of age the two children were moved to Henry's court at Madrid and were placed in Queen Juana's household. During this period it is rumored that Queen Juana tried to poison Alfonso on at least one occasion, to pave the way for her own daughter to inherit the throne.

Heir to the Throne

In early 1460s, Castillian nobles became dissatisfied with the rule of King Henry IV, and believed that the daughter (Joanna, Princess of Asturias, aka "Juana la Beltraneja") that Henry's wife Queen Juana had given birth to was not sired by Henry and thus not a legitimate heir to the throne. The nobles forced Henry to repudiate Joanna in 1464 with the Representation of Burgos and recognize Alfonso as his official heir, whereby he became Prince of Asturias, a title previously held by Joanna. Henry agreed to this with the stipulation that Alfonso someday marry Joanna.

Not long after this, Henry reigned on his promise and the nobles now controlling Alfonso started an all-out civil war, clashing most notably at the Battle of Olmedo in 1467, which concluded as a draw.

However, in 1468 at the age of only 14, Alfonso died of a sickness, most likely the plague. (Although poison and slit throat as alternative causes of death have been suggested.) His sister Isabella was asked to take her brother's place as the leader of the rebels but she declined – she made peace with Henry and was recognized as his official heir, becoming Castile's next monarch when he died in 1474.

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