While Wellington concentrated his efforts on capturing the strategically important port of San Sebastián, he sent 11,000 men under the Irish-Spanish General O'Donnell to blockade Pamplona.

To prevent a French counter-attack over the Pyrenees Wellington positioned General Hill's Corps over a 50-mile (80 km) front, to cover the coastal road and the main passes over the mountains.

Having rapidly rebuilt and reorganised his forces after their defeat, the French under Marshal Nicolas Jean de Dieu Soult launched an attack towards Pamplona through the passes of Maya and Roncesvalles.

The British were badly outnumbered, John Byng's brigade on the eastern side held Bertrand Clausel's division at bay for three hours before being forced back.

Later, Wellington admitted that splitting his forces to besiege both San Sebastián and Pamplona simultaneously had been "one of the greatest faults he ever committed in war".