After the decline of Aksum, the Eritrean highlands were under the domain of the Christian Kingdom of Medri Bahri, ruled by a Bahri Negus (or Bahri Negash, meaning "sea king"). The area was at first known as ''Ma'ikele Bahri'' ("between the seas/rivers", i.e. the land between the Red Sea and the Mereb river). The entire coastal domain of Ma'ikele Bahri was under the Adal Sultanate during the reign of Sultan Badlay ibn Sa'ad ad-Din. The state was later reconquered by the Ethiopian Emperor Zara Yaqob and renamed the Medri Bahri ("Sea land" in Tigrinya, although it included some areas like Shire in Ethiopia on the other side of the Mereb, today in Ethiopia). With its capital at Debarwa, the state's main provinces were Hamasien, Serae and Akele Guzai.