In 1437, Ferdinand participated in the disastrous Siege of Tangier led by his older brother Henry the Navigator. In the aftermath, Ferdinand was handed over to the Marinid rulers of Morocco as a hostage for the surrender of Ceuta in accordance with the terms of a treaty negotiated between the rulers of Portugal and Morocco by Henry. At first, Ferdinand was held in relative comfort as a noble hostage in Asilah, but when it became apparent that the Portuguese authorities had no intention of giving up Ceuta, Ferdinand's status was downgraded, and he was transferred to a prison in Fez, where he was subjected to much harsher incarceration conditions by his jailers. Negotiations for his release continued intermittently for years, but they came to naught, and Ferdinand eventually died in captivity in Fez on 5 June 1443.