Slave routes changed throughout the late 19th and early 20th centuries in response to shifting economic demands and British efforts to interdict the the slave trade both at sea and diplomatically on land. The most prominent East African slave trading routes, which supplied the Persian Gulf with slaves, passed through Kilwa in contemporary Tanzania and then through Zanzibar onto the Persian Gulf and the Middle East. Due to British efforts to interrupt the slave trade by sea, slave trading routes eventually shifted further north on the coast of East Africa and slave traders increasingly employed a combination of sea and land routes to ensure that slaves reached market without British intervention. After the abolition of the East African slave trade in Zanzibar in 1873, new markets for slaves were found along the Iran’s Makran Coast, where abductions and sale into slavery on the Arab littoral of the Persian Gulf became increasingly common in the last decades of the 19th and first decades of the 20th century. Slaves also arrived to market in the Persian Gulf from elsewhere in the Middle East, including Yemen and the Red Sea, although such instances represented less an established trade than opportunistic abductions made possible by political instability.