Starting with the 15th century, the Danube Delta was part of the Ottoman Empire. The Treaty of Paris of 1856 which ended the Crimean War, Danube Delta together with two districts of Southern Bessarabia was included in the Principality of Moldavia and was established an international commission which made a series of works to help navigation. In 1859, it became part of the United Principalities of Wallachia and Moldavia and later Romania.