When once these noblemen had reached agreement and had sworn to help one another, honourably and loyally, in order to wrest plunder from their enemies in any way whatsoever, they concluded that the best method they could adopt in this regard was to know for certain where the Castilians would be making for and to do battle with them there at some appropriate spot. In order to make their presence more noticeable and to win more praise for their strength in battle, they sent to the Castilians a squire, Afonso Rodrigues Batissela by name, with the message that, since they had dared to make such an incursion in order to lay waste the land of the King of Portugal, their liege lord, they might deign to proceed to where they, the Portuguese, were to be found and that they would have their dinner ready and waiting. The Castilians showed themselves to be very pleased with this message, and Juan Rodríguez de Castañeda told the squire that he promised, if this were to happen, that he would reward him with a fine steed for bringing the good news.

Afonso Rodrigues went back with this reply, at which the Portuguese were delighted. Knowing that the Castilians were bound to approach via the town of Trancoso with everything that they had plundered, they drew up their battle line in a water meadow at less than half a league from the town and across which the Castilians would have to pass. The Portuguese numbered little more than 300 lances, according to what some have written. The banner of Gonçalo Vasques was guarded by 120 lances, that of Martim Vasques by 150, that of João Fernandes by 30, and those of Gil Vasques and Egas Coelho accounted for the rest. This small force then gathered together, with every man hurrying as best he could, on account of sealing this friendly alliance so suddenly and having neglected to prepare for the action which they now undertook. They possessed few well-trained foot soldiers, but amassed many more from the townships and from among the farmworkers of that region. The result was that the Castilians held the advantage in their capable light horsemen and men-at-arms, whereas the Portuguese had superior numbers in their ill-trained men on foot.