Mohammed II
Almost immediately after coming of age, Sebastian began plans for the conquest of Morocco. The Portuguese landed in Asilah in 1578, and at the Ksar El Kebir the Portuguese, along with mercenaries from various parts of Christendom, were routed along with their ally the deposed Moroccan Sultan Abu Abdallah Mohammed II. After the disastrous defeat against the Saadians of Morocco, Sebastian was almost certainly killed in battle. Many Portuguese doubted the reports of his death however, and some still expected the king to return eventually based on other accounts of the outcome of the battle, and those who opposed the pretensions of King Phillip to the throne of Portugal tended to support such a version of events, and backed the rule of King Henry or the claims of António, Prior of Crato. To such an extent that, in 1640, King John IV of Portugal had to swear to yield his throne to Sebastian (who would have been 86 years old), in case he were to return.