The Zanzibar Revolution by local African revolutionaries in 1964 overthrew the Sultan of Zanzibar and his mainly Arab government. An ethnically diverse state consisting of a number of islands off the east coast of Tanganyika, Zanzibar had been granted independence by Britain in 1963. Thereafter a series of parliamentary elections resulted in the Arab minority retaining the hold on power it had inherited from Zanzibar's former existence as an overseas territory of Oman. Frustrated by under-representation in Parliament despite winning 54% of the vote in the July 1963 election, the mainly African Afro-Shirazi Party (ASP) allied itself with the left-wing Umma Party, and early on the morning of 12 January 1964 ASP member John Okello mobilised around 600–800 revolutionaries on the main island of