Near the end of the fifteenth century the first Europeans arrived on the Kenyan coast. In 1498, a Portuguese explorer named Vasco de Gama stumbled upon the East African coast in search of China. De Gama was initially rejected by the sultan at Mombasa although his bitter rival, the sultan of Malindi welcomed the explorers. The new immigrants did not settle in quietly, however, and within a few years the Portuguese had looted and ransacked several Swahili cities.
The Portuguese remained on the East African coast for 200 years with well established trading posts. These newest immigrants spent their time trading gold from the interior and exporting slaves to work on the plantations in North America and East Indies. Portuguese rule was harsh, unpopular, and economically debilitating for the local people.
Throughout the 17th century, the Arabs attempted to reestablish links with their East African outposts. This led to an ongoing series of confrontations with the Portuguese to establish dominance. The Omani ships prevailed and by the early 1700s, the Portuguese had been routed completely. By 1720, the last remaining Portuguese left for good leaving the East African coast again under Arab control. Other than a cross overlooking the sea near Mombasa, virtually no other trace of the hated Portuguese rule remains today.
The 18th century brought an emphasis on rebuilding the cities and reestablishing the once thriving trade routes. Under the leadership of the Sultan of Oman, Seyyid Said, the Arabs worked to regain economic and political supremacy over the region. The island of Zanzibar quickly became the center of a very lucrative trade in slaves and ivory from the interior and spices from the island itself.
During this time, Arab slavers moved into the interior of Kenya with the primary goal of exploiting rivalries between local tribes. The Arabs encouraged the powerful groups to conquer their weaker neighbors and sell them into slavery. The slaves were then forced to the coast and on to Zanzibar to be traded. Both ivory and slaves were hugely profitable and Zanzibar grew rich on the trade. This pattern continued despite the public outrage in Europe demanding an end to all slave trade. Eventually, the British brought their forceful anti-slavery message directly to the Sultan as they established a consulate at his court. After years of pressure, the Sultan finally relented and agreed to ban slavery in 1847.