 his pilgrimage, Askia Mohammad obtained the title "Caliph of the Sudan" (the area now known as West Africa) from the last Abbasid caliph, al-Mutawakkil, giving his regime a new Islamic legitimacy. He brought back with him the materials to make his tomb; all the mud and wood come from Mecca. The caravan is said to have consisted of "thousands of camels." The tomb was structured as a house, with several rooms and passageways, and was sealed when Mohammed died. Askia Mohommed is the only one buried inside the tomb itself, but several other Askias are buried in the courtyard.
Mohammad's ties with the wider Islamic world were closer than those of previous monarchs in the region. He frequently consulted Islamic judges and scholars on how to best govern his empire. One of these scholars, Al-Maghili is credited with introducing Sufism to the area and spreading the idea of the Mujaddid or "Renewer of Islam" that would become an important theme in the history of the region. Another important Islamic scholar who influenced Askia Mohammad was Jalala AI-Din Al-Suyuti, an Egyptian who advised Askia Mohammad on how to tailor Islamic law to fit the special needs of the Sahara and Sahel. Even though Askia Mohammad was a pious Muslim, he retained many traditional aspects of Songhai culture and did not try to convert non-Muslims through conquest.
Through much of its history, Gao was a center of trade and learning and served as capital of the Songhai Empire. It is similar to, and culturally connected with, the great trans-Saharan trade cities of Timbuktu and Djenne. The westernmost of the three central routes ran from the Niger River at Gao north to Tripoli, Libya.
Mediterranean economies were short of gold but could supply salt, whereas West African countries had plenty of gold but needed salt. The trans-Saharan slave trade was also important. Large numbers of Africans were sent north, generally to serve as domestic servants or slave concubines. The West African states imported highly trained slave soldiers. It has been estimated that from the 10th to the 19th century some 6,000 to 7,000 slaves were transported north each year. Perhaps as many as nine million slaves were exported along the trans-Saharan caravan route.
The city of Gao was founded around the seventh century as Kawkaw, its first recorded monarch being Kanda, who founded the Za Dynasty of what became the Songhai Empire. He ensured the city’s growth by allowing trans-Saharan traders to visit and Berbers to settle. Trade increased after Za Kossoi converted to Islam in 1009.
The Mali Empire conquered Gao sometime before 1300, but Ali Golon re-established Songhai rule. A distinguished author of the period, Al-Idrissi, described it as a "populous, unwalled, commercial and industrial town, in which were to be found the produce of all arts and trades necessary for its inhabitants."
Mali was a Muslim kingdom, and under it, the gold-salt trade established in the pre-Roman era continued. Other trade goods were slaves, kola nuts from the south, and slave beads and cowrie shells from the north (for use as currency). It was under Mali that the great cities of the Niger River bend—including Gao—prospered.
By the end of the 1460s Sonna Ali Ber, the founder of the Songhai Empire, had taken Djenne and Timbuktu, thus gaining control of some of the principal trading towns of the Sahel. Ali was succeeded by Askia Mohammad I, who defeated the heir in battle in 1493, then consolidated his territorial conquests and introduced Islam as the state religion. The empire flourished for the next hundred years until the Moroccan conquest of 1591.
Askia Mohammed expanded his empire by conquest until it covered an area that stretched over 2,000 miles, from the mouth of the Gambia River in the west to Lake Chad in the east. In the process he established a strongly centralized administration, though in some cases he allowed regional kings to continue ruling as long as they paid tribute. He died in 1528.
During his rule, Gao had about 70,000 residents and a 1,000-boat navy, but Gao was largely destroyed by the 