The document discusses several major kingdoms and empires in Africa, including Aksum, Ghana, Mali, Songhai, Kilwa, and Zimbabwe. It explains that these civilizations rose to power through control of trade networks, especially the trade of gold and salt. As trade brought wealth and new ideas, many African societies integrated aspects of Islam and Arab culture while also developing powerful city-states of their own. Overall, strategic control of trade routes and the taxation of goods was a major source of power for many kingdoms and empires across Africa over time.