[4] The Sultanate's territories varied over time, and after a period of decline, the state had sovereignty over only the Zanzibar Archipelago and a 16-kilometre-wide (10 mi) strip along the Kenyan coast, with the interior of Kenya constituting the British Kenya Colony and the coastal strip administered as a de facto part of that colony.

Under an agreement reached on 8 October 1963, the Sultan of Zanzibar relinquished sovereignty over his remaining territory on the mainland, and on 12 December 1963, Kenya officially obtained independence from the British.

Africanus further noted that they all had standing agreements of loyalty with the major central African states, including the Kingdom of Mutapa.

He established a ruling Arab elite and encouraged the development of clove plantations, using the island's slave labour.

[9] The East African slave trade flourished greatly from the second half of the nineteenth century, when Said bin Sultan made Zanzibar his capital and expanded international commercial activities and plantation economy in cloves and coconuts.

[10] Zanzibar's commerce fell increasingly into the hands of traders from the Indian subcontinent, whom Said encouraged to settle on the island.

Pressed by the British, his successor, Barghash bin Said, helped abolish the slave trade in Zanzibar and largely developed the country's infrastructure.

[14] Until 1884, the Sultans of Zanzibar controlled a substantial portion of the Swahili Coast, known as Zanj, and trading routes extending further into the continent, as far as Kindu on the Congo River.

This resulted in a native uprising, the Abushiri revolt, which was suppressed by the Kaiserliche Marine and heralded the end of Zanzibar's influence on the mainland.

[16] In August 1896, following the death of Sultan Hamad bin Thuwaini, Britain and Zanzibar fought a 38-minute war, the shortest in recorded history.

It administered about 240 km (150 mi) of coastline stretching from the River Jubba via Mombasa to German East Africa which were leased from the Sultan.

The British "sphere of influence", agreed at the Berlin Conference of 1885, extended up the coast and inland across the future Kenya and after 1890 included Uganda as well.

[20]: 761  After the First World War, more immigrants arrived from Britain and South Africa, and by 1919 the European population was estimated at 9,000 strong.

[20]: 761 On 23 July 1920, the inland areas of the East Africa Protectorate were annexed as British dominions by Order in Council.