[3] Seeking to distance himself from the volatile John Okello, Karume quietly sidelined him from the political scene, although he was allowed to retain his self-bestowed title of field marshal.

[1][2] However, Okello's revolutionaries soon began reprisals against the Arab and Asian population of Unguja, carrying out beatings, rapes, murders, and attacks on property.

[1][2] He claimed in radio speeches to have killed or imprisoned tens of thousands of his "enemies and stooges",[2] but actual estimates of the number of deaths vary greatly, from "hundreds" to 20,000.

Okello formed the Freedom Military Force (FMF), a paramilitary unit made up of his own supporters, which patrolled the streets and looted Arab property.

[14] The merger was seen by contemporary media as a means of preventing communist subversion of Zanzibar; at least one historian states that it may have been an attempt by Karume, a moderate socialist, to limit the influence of the radically left-wing Umma Party.

[7] British military forces in Kenya were made aware of the revolution at 4:45 am on 12 January, and following a request from the Sultan were put on 15 minutes' standby to conduct an assault on Zanzibar's airfield.

Within hours of the revolution, the American ambassador had authorised the withdrawal of US citizens on the island, and a US Navy destroyer, the USS Manley, arrived on 13 January.

[17] The Manley docked at Zanzibar Town harbour, but the US had not sought the Revolutionary Council's permission for the evacuation, and the ship was met by a group of armed men.

[11] Just six days after the revolution, The New York Times stated that Zanzibar was "on the verge of becoming the Cuba of Africa", but on 26 January denied that there was active communist involvement.

[2] Dissatisfied with their low pay rates and with the slow progress of the replacement of their British officers with Africans,[25] the soldiers' mutiny sparked similar uprisings in both Uganda and Kenya.