mostly of Afar, Somali, Harla, Argobba, and Arab formations, supported by the Ottomans. In the mid-1520s, Imam Ahmad ibn Ibrahim al-Ghazi assumed control of Adal and launched a war against Abyssinia, which was then under the leadership of Dawit II (Lebna Dengel). Supplied by the Ottoman Empire with firearms, Ahmad was able to defeat the Abyssinians at the Battle of Shimbra Kure in 1529 and seize control of the wealthy Ethiopian highlands, though the Abyssinians continued to resist from the highlands. In 1541, the Portuguese, who had vested interests in the Indian Ocean, eventually sent aid to the Abyssinians in the form of 400 musketeers. Adal, in response, received 900 from the Ottomans. Imam Ahmad was initially successful against the Abyssinians while campaigning in the Autumn of 1542, killing the Portuguese commander Cristóvão da Gama in August that year. However, Portuguese musketry proved decisive in Adal's defeat at the Battle of Wayna Daga, near Lake Tana, in February 1543, where Ahmad was killed in battle. The Abyssinians subsequently retook the Amhara plateau and recouped their losses against Adal. The Ottomans, who had their own troubles to deal with in the Mediterranean, were unable to help Ahmad's successors. When Adal collapsed in 1577, the seat of the Sultanate shifted from Harar to Aussa in the desert region of Afar and a new sultanate began. Collapse of the sultanate After the death of Imam Ahmad, the Adal Sultanate lost most of its territory in Abyssinian lands. In 1550 Nur ibn Mujahid assumed power after he killed Abyssinian emperor Gelawdewos. Due to constant Oromo raids both Adal and Abyssinian rulers struggled to consolidate power outside of their realms. The Adal Sultanate subsequently ended due to infighting with tribes. The Adal Sultanate was weakened after the death of Emir Nur due to the Oromo raids in 1577 and its headquarter were relocated to the oasis of Aussa in the Danakil desert under the leadership of Mohammed Jasa. The Imamate of Aussa declined gradually in the next century and was destroyed by internal rebellions led by Afar and their Harla allies in 1672. Enrico Cerulli states, eventually Zeila and Harar broke free from Aussa as it deteriorated, the semitic Adal nobility now viewed the state as nothing more than a savage Afar domain that pillaged caravans. Oromo expansion After the conflict between Adal and Abyssinia had subsided, the conquest of the highland regions of Abyssinia