Many of the historic cities in the Horn of Africa such as Abasa and Berbera flourished under its reign with courtyard houses, mosques, shrines, walled enclosures and cisterns. Adal attained its peak in the 14th century, trading in slaves, ivory and other commodities with Abyssinia and kingdoms in Arabia through its chief port of Zeila. The cities of the empire imported intricately colored glass bracelets and Chinese celadon for palace and home decoration. The Adalite military was divided into several sections such as the infantry consisting of swordsmen, archers and lancers that were commanded by various generals and lieutenants. These forces were complemented by a cavalry force and eventually, later in the empire's history, by matchlock-technology and cannons during the Conquest of Abyssinia. The various divisions were symbolised with a distinct flag. The Adal soldiers donned elaborate helmets and steel armour made up of chain-mail with overlapping tiers. The Horsemen of Adal wore protective helmets that covered the entire face except for the eyes, and breastplates on their body, while they harnessed their horses in a similar fashion. In siege warfare, ladders were employed to scale buildings and other high positions such as hills and mountains. Lewis writes: Ethnic Somalis being the majority of the army is further evidenced in the "Oxford History of Islam":  The Abyssinian–Adal war was a military conflict between the Ethiopian Empire (Abyssinia) 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 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.