Final answer:
The Portuguese disrupted the complex cultures and economies of West Africa in the 15th century by constructing trading outposts, engaging in slave trade, and diverting traditional trade routes, while African empires faced internal and external challenges.
Step-by-step explanation:
During the advent of the Portuguese in West Africa, the region was undergoing significant upheaval. The highly evolved medieval African civilizations were experiencing internal strife—the Malian Empire, for example, was weakened by rebellions and external attacks. The arrival of the Portuguese further complicated matters, as they initiated the Trans-Atlantic slave trade and diverted trade routes. As they established trade networks, the Portuguese constructed stone fortresses known as feitorias along the coast, to act as trading posts and holding areas for slaves. Indigenous kingdoms and leaders were engaged through diplomacy, exchanging gifts and goods to grant trading permissions.
The Portuguese sought gold and spice trade routes to Asia but found lucrative opportunities in West Africa. The stories of Mansa Musa's vast gold reserves enticed them, leading to their naming of present-day Ghana as the "Gold Coast." Portuguese ventures also diminished the monopoly Muslim North Africans had on sub-Saharan gold and spice trade routes. In less than forty years, the islands of São Tomé and Príncipe became a hub for the trans-Atlantic slave trade, leading to increased raids and tensions among African polities.