portions of the nation came under the direct influence of the Ottoman Empire during the 16th century. Thereafter, the region was known to the British as the "Pirate Coast", as raiders based there harassed the shipping industry despite both European and Omani navies patrolling the area from the 17th century into the 19th century. British expeditions to protect the Indian trade from raiders at Ras al-Khaimah led to campaigns against that headquarters and other harbours along the coast in 1819. The next year, a peace treaty was signed to which all the sheikhs of the coast adhered. Raids continued intermittently until 1835, when the sheikhs agreed not to engage in hostilities at sea. In 1853, they signed a treaty with the United Kingdom, under which the sheikhs (the Trucial Sheikhdoms) agreed to a "perpetual maritime truce". It was enforced by the United Kingdom, and disputes among sheikhs were referred to the British for settlement.