Since the Master realised that one of the things which were most essential to him, as he was about to be besieged, was a plentiful supply of provisions, he decided, before the King of Castile's arrival, to send men out to forage for food in areas which had not declared for him, in order to provide the city with as much food as possible.

He sent Nuno Álvares to Sintra, to bring provisions from that area, sending with him some 300 lances, both squires and citizens, and a few foot soldiers. Sintra had declared for the King of Castile and was governed at that time by the Count [of Seia] Don Enrique [Manuel de Villena] and by soldiers with whom he was well capable of defending it. Nuno Álvares roamed all around the surrounding area without encountering anybody to hinder him. He amassed plenty of provisions, both livestock and wheat, as well as other foodstuffs, and they loaded all this onto mules, with which they had come well prepared for this purpose. Nobody emerged from the town in an attempt to prevent him doing so.

The King of Castile, who was in Santarém, had just a short while beforehand sent forth Don Pedro Fernández Cabeza de Vaca, who was the Master of Santiago, Pedro Fernández de Velasco, who was his lord chamberlain, Pedro Ruiz Sarmiento, who was the Chief Provincial Governor of Galicia, and with them 1,000 lances consisting of valiant men-at-arms. Their mission was to reach the outskirts of Lisbon in order to begin to lay siege to the city, and they were to prevent those inside the city from making any sorties into the surrounding area and causing any damage whatsoever. On the night after Nuno Álvares left Sintra with his booty, he received a message informing him that these forces were in Alenquer and were preparing to attack him. Consequently, a number of his company immediately left and made for the city [of Lisbon]. Next day those who had remained behind urged him to hurry away and not wait for these forces to arrive, but Nuno Álvares refused to do so, gave no heed to anything they said and proceeded slowly and steadily with the train of booty he was driving. On the way and much against everybody's wishes he waited till midday to see whether the Castilians would arrive to confront him.