Peter, Duke of Coimbra
Under king Edward, the colony at Ceuta rapidly became a drain on the Portuguese treasury, and it was realised that without the city of Tangier, possession of Ceuta was worthless. In 1437, Duarte's brothers Henry and Ferdinand persuaded him to launch an attack on the Marinid sultanate of Morocco. The expedition was not unanimously supported: Infante Peter, Duke of Coimbra, and the Infante John were both against the initiative; they preferred to avoid conflict with the king of Morocco. Their instincts proved to be justified. The resulting attack on Tangier, led by Henry, was a debacle. Failing to take the city in a series of assaults, the Portuguese siege camp was soon itself surrounded and starved into submission by a Moroccan relief army. In the resulting treaty, Henry promised to deliver Ceuta back to the Marinids in return for allowing the Portuguese army to depart unmolested. Duarte's youngest brother, Ferdinand, was handed over to the Marinids as a hostage for the final handover of the city.