The Abbasid caliphs al-Manṣūr (754–775), Hārūn al-Rashīd (786–809) and al-Maʾmūn (813–833) are reputed to have sent punitive expeditions to the Islamized city-states of the Somali coast and set up governors there.
[5][7][8][9] The sultans of Mogadishu, Mārka, Barāwa, Faza, Sīwī, Bata, Manda (Munda), Ṭaqa, Lamu (Āmu), Ūzi, Malindi (Malūdi), Uyūmba, Kilifi, Basāsa, Zanzibar, Kilwa and Waybu (possibly a tributary of the Shebelle) are among those who accepted the emissary.
[10] The Persians were loyal for many years, but they stopped sending the kharāj even during the reign of Hārūn and entered open rebellion during the Miḥna of al-Maʾmūn, when he espoused the createdness of the Quran.
The Zanj[c] sent a manifesto to Baghdad and the caliph sent an army of 50,000 (raised either in Iraq or Egypt) to Malindi, which caused the leaders of the rebellion to flee into the nyika (brush country).
He suggests that if the accounts in the Book of the Zanj bear any relation to history it is probably to be found in the early settlement of Muslims on the East African coast associated with this coin find.