Geography of Asia though the Middle East is a division of Asia. The demarcation between Asia and Africa is the isthmus of Suez and the Red Sea. The border with Europe starts with the coast of the eastern Mediterranean, even though Turkey in the Near East extends partly into the Aegean Islands and includes Istanbul on the European side of the Bosphorus. On the north the boundary between the continents of Asia and Europe is commonly regarded as running through the Dardanelles, the Sea of Marmara, the Bosporus, the Black Sea, the Caucasus Mountains, the Caspian Sea, the Ural River to its source,
East Africa main goal on the Swahili coast was to take control of the spice trade from the Arabs. At this stage, the Portuguese presence in East Africa served the purposes of controlling trade within the Indian Ocean and securing the sea routes linking Europe to Asia. Portuguese naval vessels were very disruptive to the commerce of Portugal's enemies within the western Indian Ocean and were able to demand high tariffs on items transported through the sea due to their strategic control of ports and shipping lanes. The construction of Fort Jesus in Mombasa in 1593 was meant to solidify Portuguese hegemony