In 1806 he became ruler (Sayyid) of Oman, with his capital at Muscat on the Persian Gulf. In 1822, assisted by the British, he sent an expedition to Mombasa, whose rulers, the Mazrui family, owed him nominal allegiance, but who were seeking independence. He himself visited Mombasa in 1827 and in the next decade brought many East African ports under his control. In 1837 he ended Mazrui rule in Mombasa and signed commercial agreements with Britain, France, and the USA. He first visited Zanzibar in 1828, buying property and introducing clove production. In 1840 he took control of Zanzibar. Said sent trading caravans deep into Africa, seeking ivory and slaves, and Zanzibar became the commercial capital of the East African coast. Although an ally of the British, he was under constant pressure from them to end his trade in slaves, and he signed an agreement to do this in 1845. When he died, he divided the Asian and African parts of his empire between his two sons.