Two months after the decisive Portuguese victory in the Battle of Aljubarrota, the Constable of Portugal Nuno Álvares Pereira had decided to take the offensive and invade Castile.
The Castilian reinforcements were made up mainly of local townspeople and the army numbered about 20,000 men, with the presence of several nobles.
[3] Nuno Álvares Pereira then ordered his army to form a square with the baggage on the center, and impetuously crossed the Castilian forces, which attempted to oppose him.
Upon reaching the river shore, Nuno Álvares Pereira ordered his rearguard to protect the baggage and fight the enemy, while with his vanguard he crossed over.
[5] With his fall and the overthrow of his standard, the Castilian army demoralized and was soon broken and in disorder, and could not stop the Portuguese attack, being quickly and totally defeated.