The vast hinterland of Zanzibar was structurally weak but, although it suffered repeatedly from conflicts in the interior, it did not break apart until European colonial powers intervened in the 1880s to partition it among themselves. Economically the commercial empire was fragile, as was demonstrated by the American Civil War, but it was also resilient. The empire had been integrated more generally into the international economic system so that it could absorb economic shocks and diversify its markets and the commodities it could offer for export. However, throughout the nineteenth century various constraints had been imposed on it. Because of its economic dependence on international trade these gradually restricted its ability to respond to economic shocks. The commercial treaties with the various Western powers had tied the hands of Zanzibar to the maximum of 5 per cent duty on imports without obtaining reciprocal privileges for Zanzibar, and the ‘most favoured nation’ clause did not prevent the United States from clamping a 40 per cent import duty on Zanzibar cloves. Even the ‘Mrima reservation’ introduced in the treaties with the European powers was legally inoperative since it was not included in the treaty with the United States, and the Americans were able to use the threat of trading directly on the mainland to blackmail Seyyid Said into suspending his plans for direct trade with the United States. Finally, the treaties granted foreign powers ‘extra-territorial rights’ not only over their own nationals and over disputes between foreign nationals, but also over Zanzibar subjects in the employ of these nationals.

More crucially, however, the commercial empire was becoming politically subverted by British imperialism. British influence over the Busaidi dynasty, of course, went back to the end of the eighteenth century when the special unequal relationship developed between the Omani state and the British in India, who were determined to maintain their dominance over the trade of the Persian Gulf. The various slave trade treaties provided a convenient path for the penetration of British influence and power into East Africa under a humanitarian guise, and were a prelude to British supremacy at Zanzibar. The emergence of the Indians as the most powerful local merchant class provided Britain with a second way of exerting its influence on the policies of the commercial empire under the excuse that they were British subjects.