Trade between East Africa, Middle and Far East was disturbed by Portuguese invasion along the coast in the 16th Century and 17th Century. The Portuguese attempted of capture and control the Indian Ocean trade and this led to wars.The Portuguese invasion on the East African coast caused four major changes in the pattern of trade:
1. There was diversion of the major trade routes especially in connection to with copper and gold. These items were now shipped overseas from Sofala southwards and through the Atlantic Ocean.
2. Conflict developed between African gold miners and Portuguese traders. The Portuguese sought control of gold production and this was resisted by African miners and there was a decline in the output of gold.
3. Portuguese imposed trading licenses and permits on African and Arab traders. This led to further decline of trade between East Africa and Asia.
4. Coastal City states such as Kilwa began to decline because their prosperity depended on gold trade. This meant the African and Arab traders who acted as middlemen also lost business.