The Adal Sultanate was a 10th to 16th century mediaeval Islamic state in what is now Djibouti and Somalia. The capital of Adal was Harar, and there were several significant trading ports, such as Zeila, on the Gulf of Aden and Red Sea.
The Sultanate reached its peak in the first half of the 16th century when it campaigned against neighboring Christian Ethiopia. What started as simple border raids and skirmishes led by Mahfuz, the governor of Zeila (a port on the Gulf of Aden also known as Zayla or Saylac), in the first two decades of the 1500s escalated into the Adal-Ethiopian War (1529-43). Mahfuz' son-in-law, Ahmad Grāñ, took control of the Sultanate, installing his half-brother Barakat ibn Umar Din as Sultan.
In 1529 Ahmad Grāñ declared a jihad against Emperor Dawit II of Ethiopia and his Christian followers. His army, reinforced by nomadic Issa and Oromo fighters from Somalia and janissaries from the Ottoman Empire, swept into Ethiopia, driving up from the south, destroying monasteries and churches, and converting the people to Islam as they went. By 1533 Ahmad Grāñ controlled all but the northern highlands, but it was there he finally met his match.
The Ethiopian Emperor, Dawit II, appealed to the Portuguese for aid, and although it arrived too late for Dawit II, his successor Emperor Galawdewos was able to drive Ahmad Grāñ's forces back south, until they were finally defeated at the Battle of Wayna Daga on 21 February 1543. Ahmad Grāñ's half-brother, the sultan was killed by Emperor Galawdewos' forces a decade later when they sacked the Adal capital Harar.
With the fall of Ahmad Grāñ's dynasty, the Ottomon Empire lost interest in Adal and refused to provide further aid. In the second half of the 16th century Adal faced an additional threat: the Oromo to the south west. Military expansion by the Oromo led to the Sultan and his Imans fleeing into the desert, leaving a political vacuum which was filled by the Oromo elite. Adal was incorporated by its neighbors.