The Abyssinian–Adal war was a military conflict between the Ethiopian Empire and the Adal Sultanate that took place from 1529 until 1543. Abyssinian troops consisted of Amhara, Tigrayan and Agew ethnic groups. Adal forces consisted mostly of Somali.^[2] with Afar, Harari, Argobba forces ,^[5]

Islam was introduced to the Horn of Africa early on from the Arabian peninsula, shortly after the hijra. In the late 9th century, Al-Yaqubi wrote that Muslims were living along the northern Somalia seaboard.^[6] He also mentioned that the Adal kingdom had its capital in the city,^[6][7] suggesting that the Adal Sultanate with Zeila as its headquarters dates back to at least the 9th or 10th centuries. According to I.M. Lewis, the polity was governed by local Somali dynasties, who also ruled over the similarly-established Sultanate of Mogadishu in the Benadir region to the south. Adal's history from this founding period forth would be characterized by a succession of battles with neighbouring Abyssinia.^[7] Ahmed fighters were using bows and arrows.^[8]

Imam Ahmad ibn Ibrahim al-Ghazi was a military leader of Somali ethnicity of the medieval Adal Sultanate in the northern Horn of Africa. Between 1529 and 1543, he defeated several Ethiopian emperors and embarked on a conquest referred to as the Futuh Al-Habash ("Conquest of Abyssinia"), which brought three-quarters of Christian Abyssinia under the power of the Muslim Sultanate of Adal.^[9][10] With an army mainly composed of Somalis,^[11] Al-Ghazi's forces and their Ottoman allies came close to extinguishing the ancient Ethiopian kingdom. However, the Abyssinians managed to secure the assistance of Cristóvão da Gama's Portuguese troops and maintain their domain's autonomy. Both polities in the process exhausted their resources and manpower, which resulted in the contraction of both powers and changed regional dynamics for centuries to come. Many historians trace the origins of hostile Ethiopia–Somalia relations to this war.^[12] Some scholars also argue that this conflict proved, through their use on both sides, the value of firearms such as the matchlock musket, cannons and the arquebus over traditional weapons.^[13]

In 1529, Imam Ahmad's Adal troops defeated a larger Ethiopian contingent at the Battle of Shimbra Kure. The victory came at a heavy cost but it solidified the Somali forces' morale, providing proof that they could stand up to the sizable Ethiopian army.

The victories that gave the followers of Imam Ahmad the upper hand came in 1531. The first was at Antukyah, where cannon fire at the start of the battle panicked the Ethiopian soldiers. The second was on 28 October at Amba Sel, when troops under the Imam not only defeated but dispersed the Ethiopian army and captured items of the Imperial regalia. These victories allowed the Somalis to enter the Ethiopian highlands, where they began to sack and burn numerous churches, including Atronsa Maryam, where the remains of several Emperors had been interred.^[14] The country was looted by the Ahmad's forces, who destroyed several Christian monuments and oppressed the non-Muslim Amhara and Tigray.

Dawit II died in 1540 and his son Menas and latter emperor was captured by the forces of Imam Ahmad; the Empress was unable to react as she was besieged in the capital. In 1543, Ethiopian guerrillas were able to defeat the Somalis with the help of the Portuguese navy, which brought 400 musketeers led by Cristóvão da Gama via Massawa, a port in the Eritrean Kingdom of Medri Bahri, an important port today in present-day Eritrea. Although, Da Gama was captured in the battle of Battle of Wofla, and later killed.

The 500 musketeers were led by Bahri Negassi Yeshaq, king of Medri Bahri. Yeshaq not only provided the Portuguese with provisions and places to camp in his realm but also information about the land. The Bahr negus also joined Emperor Gelawdewos and the Portuguese in the decisive Battle of Wayna Daga, where Imam Ahmad was killed. The death of Imam Ahmed and the victory in the Battle of Wayna Daga caused a semi-collapse of Ahmed forces and forced a Somali retreat from Ethiopia.

Mohammed Hassan has plausibly argued that because this conflict severely weakened both participants, it provided an opportunity for the Oromo people to migrate into the lands south of the Abay east to Harar and establish new territories.^[15]