6 ideas
The Omani Sultanate at Zanzibar ruled the mainland mainly by controlling the trade routes and the coastal ports through which interior goods had to pass. It did not govern the interior as territory. Political authority followed commercial networks, so the empire's reach was only as wide as the caravan routes and the customs houses that taxed them.
This turned trade revenue into a predictable state income. Customs farming also tied the ruler's fiscal survival to Indian merchant capital, which in turn became the source of credit for the caravans reaching into the interior.
Industrializing Western markets wanted soft East African ivory for piano keys, billiard balls and cutlery handles. That demand pushed coastal caravans ever deeper into the interior as elephant herds near the coast were depleted. The retreating ivory frontier reorganized African societies along the routes and pulled them into dependence on imported goods.
After Omani settlers planted cloves on Zanzibar and Pemba in the early nineteenth century, slaves were used for production as well as exported. The island's economy came to depend on a steady inflow of captive mainland labour. This fused the slave trade with plantation agriculture, so the empire's prosperity rested on continuing coercion.
Zanzibar's growth can be read as the region becoming a specialized supplier of raw commodities to an expanding world capitalist economy, not as autonomous development. Seen this way, the boom itself created the dependence. The more the economy was geared to foreign markets and foreign-held credit, the more its political sovereignty became hollow.
Britain used abolitionist treaties, from the Moresby Treaty of 1822 to the 1873 closure of the slave market, to gain leverage over successive Sultans. Humanitarian pressure thus doubled as the instrument that brought Zanzibar under British control before any formal protectorate existed.