With Lisbon under siege in this way, Pedro Ruiz Sarmiento, governor of Galicia, and Juan Rodríguez de Biedma and other nobles from that land entered Portugal across the north-west border and reached as far as Barcelos. Many men of Portugal from that district gathered to fight against them, including Don Enrique Manuel, who was the uncle of King Fernando and the brother of Doña Constanza, who had been the wife of King Pedro of Portugal, along with the knight João Lourenço Bubal and Fernão Gonçalves de Meira and Nuno Viegas the Elder, as well as other nobles and the town councils of Oporto and Guimarães. When the Castilians learned of this, they decided to await them and stationed a strong force of many men in ambush in a hidden place, of which the Portuguese knew nothing. After the battle began, the men of Portugal were getting the better of their opponents. At this point, Juan Rodríguez de Biedma came out of the ambush, making a great noise as if there were a great many men, and at once a squire who was carrying the banner of Enrique Manuel turned to flee on horseback. His men began to cry out at him: ‘The banner is fleeing, the banner is fleeing!’ ‘My friends,’ said Enrique, ‘pay no attention to the banner, which is but a small piece of cloth that is blowing away; rather, pay heed to my body, which is here, and in which you should find greater encouragement than in the banner. Therefore let us go on fighting for victory, and pay no attention to the banner.’ Then they fought on until they were defeated and totally routed.

When Nuno Gonçalves, who held the castle of Faria, saw the Portuguese going into battle, he went forth from the town with some of his men, thinking to attack the enemy by surprise, and hoping that some of the Portuguese from one side and some from the other might catch the Castilians in the middle. The Castilians, who had already beaten the first force, turned on him, and he was defeated and captured. João Lourenço Bubal was killed there, and Nuno Viegas and Fernão Gonçalves de Meira were taken prisoner; Enrique Manuel fled towards Ponte de Lima.