After the Roman conquest of the Nabataean Empire and the Roman naval presence at Aden to curb pillaging, Somali and Gulf Arab merchants by agreement barred Indian ships from trading in the free port cities of the Arabian peninsula to protect the interests of Somali and Arab merchants in the extremely lucrative ancient Red Sea-Mediterranean Sea commerce. However, Indian merchants continued to trade in the port cities of the Somali peninsula, which was free from Roman interference.