nominal control of the Sultans of Muscat, they were in practice run by tribal leaders and the conservative Imams of Oman, practitioners of the Ibadi sect of Islam. The Sultanate of Muscat possessed a powerful naval force, which enabled the creation of a maritime empire dating from the expulsion of the Portuguese in 1650 through the 19th century, at times encompassing modern Oman, the United Arab Emirates, southern Balochistan, and Zanzibar and the adjacent coasts of Kenya, Tanzania and Mozambique. The Sultanate of Muscat also engaged in a very lucrative slave trade across east Africa. Consolidation and decline In the early 1820s, the Sultanate lost most of its territories in the Persian Gulf, which became the Trucial States under British protection. The fifth Sultan of the Al Said dynasty, Said bin Sultan, consolidated the Sultanate's territorial holdings and economic interests and Oman prospered. However, the Omani fleet was unable to compete with the more technically advanced European fleets and the Sultanate lost much of the trade with South Asia. Pressure by the British to abandon the slave trade further led to the loss of political and economic clout of the Sultanate. On 4 June 1856, Said bin Sultan died without appointing an heir to the throne and members of the Al Said dynasty could not agree on a ruler. Through British mediation, two rulers were appointed from the Al Said clan; the third son of the Sultan, Thuwaini bin Said became ruler of the mainland. His sixth son, Majid bin Said, became ruler of an independent Sultanate of Zanzibar on 19 October 1856. The Sultans of Zanzibar were thereafter obliged to pay an annual tribute to Muscat. The Imamate cause was renewed in the interior of Oman due to the development of British imperialism in the coastal Oman, the Sultanate of Muscat. In 1913, a rebellion was led by Imam Salim Alkharusi against Muscat to reestablish an Imamate in the interior region of Oman. The Imamate, similar to the Sultanate, was ruled by the Ibadi sect, however, the dispute between both parties was for the most part political. The Omanis in the interior believed that the ruler should be elected and rejected British control over the Sultanate. The Sultanate was however able to defend itself with British help. This historical split continued throughout much of the twentieth century with Sultan Taimur bin Feisal granting limited autonomy to the Imamate of