The site of the ancient Bronze Age civilization of Dilmun, Bahrain was a trade hub linking Mesopotamia and the Indus valley until a drop in trade from India caused the Dilmun civilization to decline around 2,000 B.C. The inhabitants of Bahrain converted to Islam in the 7th century. Bahrain subsequently fell under the control of Islamic caliphates based in Damascus, then Baghdad, and later Persian, Omani, and Portuguese forces.