The Sahel
The Sahel is a geographical designation for the area in Africa which divides the Saharan desert from the wooded savannas to the south. It is a transitional band of land running across the continent touching many countries including; Senegal, Mauritania, Mali, Burkina Faso, Algeria, Niger, Chad, Nigeria, Sudan, Somalia, Ethiopia and Eritrea. It is an arid plain broken by occasional mountain ranges. A harsh, unforgiving country populated by nomadic peoples, but from the Sahel sprung many of the greatest African empires.
The importance of the Sahel stems from the great trans-Saharan trade route - the main conduit for moving goods from one side of the continent to the other. Gold, slaves and ivory moved from West Africa across to either the great Mediterranean ports or to the Arabian Peninsula. In return salt and other goods flowed in return. The route was well established from ancient times and was of key importance to the Egyptians, the Roman Empire and remained so into the medieval period.

The trade routes were the life blood of the Sahel. Much as the growth of the railway in the American west led directly to urban development, the trade routes were directly responsible for where cities sprung up in the Sahel. Located by strategic watering holes and oasis, placed at points ideal for further dispersion of goods, the empires of the Sahel began as trade oriented city states. The empires that controlled trade controlled the region. Gaining wealth and influence that was renowned from Arabia to Europe.

Various kingdoms sprang into existence from the 700s AD. - The most prominent early empire being the Ghanan Empire. Arab traders greatly influenced the growth of these early kingdoms. Their explorations and trade efforts created a reason for local kingdoms to expand and seek to dominate trade routes. Which, due to Arab traders were becoming valuable commodities? But perhaps the most influential moment in the history of Sahelian kingdoms occurred when around the 1070s AD when the Almoravid Empire established itself in a territory which by 1120 AD extended from Spain across the Sahara into the Sahel displacing the regional influence of the Ghana Empire. The Almoravids established a territory which opened up more direct travel and influence between North Africa and Europe. The extent of their efforts is clearly stamped into the architecture of southern Spain. The spread of Islam under the Almoravids established cultural norms which would continue into the present day in the Sahel.
However the Almoravids were a Berber people with their roots in North Africa. The next great Sahel Empire rose from the ashes of the Ghana Empire and is known as the Mali Empire. Based around the great Niger River and extended as far east as Timbuktu. The Mali Empire controlled many vassal states. These usually consisted of trading towns whose local rulers fell under the sway of the empire. However the Mali Empire had increasing trouble controlling its vassal states and in 1340 AD the Songhai people successfully established their own empire and gradually expanded to become the largest African empire ever seen. Controlling the great trading towns of the Sahel, Timbuktu and Gao, the empire reached from the Atlantic Ocean in West Africa across what is present day Niger.
More than gold and salt flowed on the trade routes. Islamic scholarship flourished with great libraries established and scientific as well as religious study encouraged. The empire was not simply a collection of trading outposts but a center for cultural growth and understanding. The Songhai Empire encompassed numerous ethnic groups and a territory greater than Western Europe. It was an empire of many facets with a shrewd foreign policy relying on not just strength of arms but diplomacy. All of this was tied under a banner of Islam. Various leaders of Songhai during different periods made their hajj to Mecca - illustrating the relative ease of travel over tremendous distances inside the lands of the empire.
The military might of Songhai is a perfect example of the normal pattern for Sahel armies. The cavalry was all important. Drawn from wealthy retainers, the nobility and any others who could afford horse and equipment, the cavalry was the force that broke the backs of the enemy. The geography of the Sahel made cavalry a natural pinnacle of local armies. Broad plains allowed for swift charges and the lack of cover meant infantry had difficulty defending against armored horsemen. This natural dominance led to cities increasingly investing in extensive earthworks and fortifications with the result that siege warfare became common.
The Sahel states were not only subsisting on trade. The Hausa lands, in what is modern day Nigeria, were made up of heavily fortified city states which occasionally worked in concert but mainly remained separate entities. The Hausa were well known as traders but their cities also gained a reputation for industrial output. Particularly in arms and armor the Hausa were well known for iron and steel working, blade manufacture and export. Their states formed a well-equipped manufacturing region which exported both goods and craftsmen both to the east and west of their own territory.
Perhaps the best comparison cosmopolitan nature of Sahel society and trading centers is the silk route in Asia. Cities did not have a homogenous ethnic population and frequently changed ruling hands over the centuries. For example Timbuktu was at various times part of the Mali Empire, Tuareg, Songhai, Fulani and more. The struggle to control trade was paramount.
The sociographic and geopolitical context that arises from the Sahel is one of organized city states, empires consisting of multiple holdings of city states and on the edges predatory nomadic groups capable of capturing and controlling trade routes themselves. The city centers or what we could perhaps term heartlands, were not only economically powerful but important religious and cultural centers with influence spreading to surrounding areas.