On 10 July the Liberal English admiral George Rose Sartorius sent his boats into the mouth of the River Douro and fought back the Royalists' fire.

While protected by the Liberal fleet, the division of Lieutenant-Colonel John Schwalbach crossed the river and occupied the Serra do Pilar, in Gaia, forcing the Royalists to withdraw in disorder to Oliveira de Azeméis.

He dispatched Pedro de Sousa Holstein, 1st Duke of Palmela, to London, with the mission of obtaining financial support to the cause and contracting officers and soldiers.

Due to the rivalry between Santa Marta and Póvoas, the Royalist troops came to be commanded by General Gaspar Teixeira, Viscount of Peso da Régua.

To the south the lines began at Cabedelo in Canidelo, on the opposite side of the mouth of Douro, and ended at Pedra Salgada, next to the hill of the Seminar, placing fifteen batteries in this area.