In preparing for the siege of this formidable place Ferdinand called upon all the cities and towns of Andalusia and Estramadura, and the domains of the orders of Santiago, Calatrava, and Alcantara, and of the priory of San Juan, and the kingdom of Toledo, and beyond to the cities of Salamanca, Toro, and Valladolid, to furnish, according to their repartimientos or allotments, a certain quantity of bread, wine, and cattle to be delivered at the royal camp before Loxa, one half at the end of June and one half in July.

These lands, also, together with Biscay and Guipuscoa, were ordered to send reinforcements of horse and foot, each town furnishing its quota, and great diligence was used in providing lombards, powder, and other warlike munitions.
The Moors were no less active in their preparations, and sent missives into Africa entreating supplies and calling upon the Barbary princes to aid them in this war of the faith.

To intercept all succor, the Castilian sovereigns stationed an armada of ships and galleys in the Straits of Gibraltar under the command of Martin Diaz de Mina and Carlos de Valera, with orders to scour the Barbary coast and sweep every Moorish sail from the sea.
While these preparations were making, Ferdinand made an incursion at the head of his army into the kingdom of Granada, and laid waste the Vega, destroying its hamlets and villages, ravaging its fields of grain, and driving away the cattle.
It was about the end of June that King Ferdinand departed from Cordova to sit down before the walls of Loxa.

So confident was he of success that he left a great part of the army at Ecija, and advanced with but five thousand cavalry and eight thousand infantry.

The marques of Cadiz, a warrior as wise as he was valiant, remonstrated against employing so small a force, and indeed was opposed to the measure altogether, as being undertaken precipitately and without sufficient preparation.