When King Fernando saw that the King of Castile was bypassing Santarém and going on to attack Lisbon, he decided to send men there to aid in its defence. Since Count Álvaro Pérez de Castro was the governor of the city, the king commanded him to go to the castle, for the safety and protection of the city, and ordered all houses adjoining the city wall to be destroyed, so that the Castilians might not find shelter in them and cause harm in that way. Moreover, he sent the Admiral Master Lançarote and Vasco Martins de Melo and Juan Fozín, who was the captain of the fleet, and several other knights, both from among those who were with him and those who had come in the retinue of the queen when she left Coimbra and came to Santarém. They came in barges and entered the city, because the fleet of the King of Castile had not come yet to prevent them from entering.

Having had news that the galleys of Castile were coming from Seville well armed, they agreed that it was a good idea to arm four galleys that lay at anchor before the city, along with several naos, and to sail out to confront the Castilian galleys and fight with them. Thus it was that they made ready and set out from the port. Not having gone far, they caught sight of several galleys that were coming ahead. Captain Juan Fozín, who was in one of the naos, wanted the Portuguese to attack them, giving his assurance that they would defeat them, since their [own] naos and galleys were well armed, and the Castilian vessels were not. The admiral, with great cowardice and lack of initiative, though he had the advantage over his adversaries, refused to agree to the attack. Instead, he said that they should taunt them and fight with them in front of the city, so that everyone could enjoy watching the victory.

The Castilian galleys that were ahead, with the great apprehension and fear they were feeling, when they got close to the city tried hard to get across the river.