Ferdinand III was one of the most successful kings of Castile, securing not only the permanent union of the crowns of Castile and León, but also masterminding the most expansive southward territorial expansion campaign yet in the Guadalquivir Valley, in which Islamic rule was in disarray in the wake of the defeat of the Almohad caliphate at the Battle of Las Navas de Tolosa.

His repeated and decisive victories against the Islamic Caliphate earned him the title Athleta Christi, meaning 'Champion of Christ', which was conferred upon him by Pope Gregory IX.

[2] By military and diplomatic efforts, Ferdinand greatly expanded the dominions of Castile by annexing the crown of Guadalquivir river valley in the south of the Iberian Peninsula, establishing the boundaries of the Castilian state for the next two centuries.

New territories included important cities such as Baeza, Úbeda, Jaén, Córdoba and Seville, that were subject of Repartimiento, given a new general charter and repopulated in the following years.

[7] The marriage of Ferdinand's parents was annulled by order of Pope Innocent III in 1204, due to consanguinity, but the legitimacy of the children was recognized.

Alfonso of León considered himself tricked, and the young king had to begin his reign by a war against his father and a faction of the Castilian nobles.

The resulting treaty of Benavente was signed on 11 December 1230, by which Ferdinand received the Kingdom of León, in return for a substantial compensation in cash and lands for his half-sisters, Sancha and Dulce.

The Andalusian-based claimant, Abdallah al-Adil, began to ship the bulk of Almohad arms and men across the straits to Morocco to contest the succession with his rival there, leaving al-Andalus relatively undefended.

In payment, al-Bayyasi gave Ferdinand the strategic frontier strongholds of Baños de la Encina, Salvatierra (the old Order of Calatrava fortress near Ciudad Real) and Capilla (the last of which had to be taken by siege).

Seeing the opportunity, the Christian kings of the north – Ferdinand III of Castile, Alfonso IX of León, James I of Aragon and Sancho II of Portugal – immediately launched a series of raids on al-Andalus, renewed almost every year.

There were no great battle encounters – Ibn Hud's makeshift Andalusian army was destroyed early on, while attempting to stop the Leonese at Alange in 1230.

The capture of Córdoba was the result of a well-planned and executed process whereby parts of the city (the Ajarquía) first fell to the independent almogavars of the Sierra Morena to the north, which Ferdinand had not at the time subjugated.

[11] Ferdinand set up a council of partidores to divide the conquests and between 1237 and 1244 a great deal of land was parcelled out to private individuals and members of the royal family as well as to the Church.

Whereas the Benedictine monks, and then the Cistercians and Cluniacs, had taken a major part in the Reconquista up until then, Ferdinand founded houses for friars of the Dominican, Franciscan, Trinitarian, and Mercedarian Orders throughout Andalusia, thus determining the future religious character of that region.

His biographer, Sister María del Carmen Fernández de Castro Cabeza, A.C.J., asserts that, on his deathbed, Ferdinand said to his son "you will be rich in land and in many good vassals, more than any other king in Christendom.

[18] Today, the incorrupt body of Saint Ferdinand can still be seen in the Cathedral of Seville, for he rests enclosed in a gold and crystal casket worthy of the king.

[23] This is because La Laguna is a suffragan diocese of the Archdiocese of Seville whose capital city has Saint Ferdinand as one of its co-patrons, together with the Virgen de los Reyes.