In 1372 the English monarch Edward III planned an important campaign in Aquitaine under the new lieutenant of the Duchy, the Earl of Pembroke. The English rule in Aquitaine was by then under threat. Since 1370 large parts of the region had fallen under French rule. In 1372, Bertrand du Guesclin lay siege at La Rochelle. To respond to the demands of the Franco-Castilian alliance of 1368, the king of Castile, Henry II of Trastámara, dispatched a fleet to Aquitaine under Ambrosio Boccanegra.

John Hastings, 2nd Earl of Pembroke had been dispatched to the town with a small retinue of 160 soldiers, £12,000 and instructions to use the money to recruit an army of 3,000 soldiers around Aquitaine for at least four months. The English fleet probably consisted of 32 ships and 17 small barges of about 50 tons.

The Castilian victory was complete and the entire convoy was captured. This defeat undermined English seaborne trade and supplies and threatened their Gascon possessions. The battle of La Rochelle was the first important English naval defeat of the Hundred Years' War. The English needed a Year to rebuild their fleet through the efforts of fourteen towns.