The Moroccan citadel of Ceuta, on the southern side of the Strait of Gibraltar, had been seized in 1415 in a surprise attack by the Kingdom of Portugal. (See Conquest of Ceuta). The Marinids had tried to recover it in 1418–1419, but failed. The assassination of the Marinid sultan in 1420 sent Morocco reeling into political chaos and internal disorder for the next few years, giving the Portuguese time to entrench themselves in Ceuta.