This was a world of sailing ships, large ocean-going dhows, and smaller coasting vessels. The monsoon wind system still facilitated and constrained maritime trade in the Indian Ocean basin, just as it had for two millennia. British and French commerce and naval power had displaced that of the Portuguese (who remained in Goa, however). European sailing ships required deeper harbors than those of their Asian competitors, whose crews included many African sailors. Europeans would rely on sails rather than steam for much longer here than in the Atlantic, where coal was much less expensive. So, there was continuity in the basic technology of trade for most of the period covered by the timeline.
After the Omanis expelled the Portuguese from Muscat in 1650, they helped the Swahili towns of East Africa in their struggle to extricate themselves from the Portuguese yoke. After the 1698 fall of Fort Jesus, although Oman claimed virtually the entire Swahili coast, Omani rulers were too weak internally to enforce their claims. Swahili towns rebelled, but they were no more involved in the export trade than they had been under the Portuguese. For Arab and Indian traders, the great boon of Portugal's decline was the return to older patterns of trade. In the western Indian Ocean basin, these patterns favored Oman because Muscat was well-placed to dominate the Persian Gulf. Trade with India increased steadily, Omani merchants prospered, and Oman emerged as a key player in the Indian Ocean trade. This created considerable anxiety among the system's European players, and the British treaty with Oman in 1799 reflects this anxiety. The British, of course, wanted to protect their interests in India.
Mercantile rivalry between Britain and France, played out globally in the eighteenth century, provides a larger context for relations among Europeans, Indians, Arabs, and Africans in the Indian Ocean system. In the decades after 1760, France was losing out to Britain. A key event was the 1757 British triumph in India, giving the British control over Bengal and greater influence in the interior. The French then turned their attention to the French East India Company's bases on Mauritius and Reunion, where they had developed sugar plantations in the 1740s with slaves obtained from Madagascar. When these plantations required more labor, the French went looking for slaves on the East African coast. Also propelling the French was a concurrent increase in the demand for labor in the French West Indies.
In the 1770s, Kilwa was open to new commercial opportunities. Its merchants were already exporting ivory and slaves (also tortoise shell, cowries, and gum) and importing cloth, hardware, dates, salt, arms, and ammunition. Kilwa's advantage was a long-distance trade route that greatly enlarged its hinterland while other Swahili towns were still trading indirectly with the interior. This trade was in the hands of African peoples, especially the Yao, who carried ivory to the coast. The demand for ivory in India was increasing, so prices were rising. When the Portuguese decided to impose high duties on ivory exports from Mozambique, the ivory trade shifted to Kilwa. For Mozambique, this meant that traders turned to the slave trade; raiding devastated the interior, a tragedy that continued well into the nineteenth century, when slaves were sent to Brazil, Cuba, even the United States. When French traders came to Kilwa seeking slaves, they gave a major boost to Kilwa's export slave trade. The ruler of Oman wanted to tax this trade, so he tried to exert more control over Kilwa. Also, Omani prosperity had generated a greater demand for slaves in Oman itself, where slaves worked on date plantations, crewed ships, and served as domestics.
This expansion of maritime trade on the East Coast was centered on Kilwa from the 1770s to 1790s, but it initiated a process that came to full fruition in Zanzibar in the first half of the nineteenth century. In the 1780s, Zanzibar was the only part of the East Coast loyal to Oman, but Omani traders recognized its potential. Another critical enabling factor was the Industrial Revolution in the West. British textile mills were already producing cheap cloth for export to overseas markets. European prosperity would soon create a desire for luxury goods that included an almost insatiable demand for ivory. Thus, several factors that would shape eastern Africa's integration into the world economy during the nineteenth century were in place by the turn of the century.