Establishment and modification of the border along the segment of southern Bessarabia throughout the 19th century

At the beginning of the 19th century the Russian Empire managed to seize the territory of the eastern part of Moldova, located between the rivers of Dniester, Prut, and Danube and the Black Sea, which has since been called Bessarabia. The inclusion of only this territory of the Romanian principalities in the Russian Empire was not the initial plan of the Russian authorities, but it was the last opportunity, in the run-up to the French offensive, at least with some result, to end the war of 1806-1812 with the Sublime Porte, a state that was considered much weaker than Russia. Although the unbending position of the Ottoman Porte in the negotiations between two parties to the armed conflict didn't allow the Russian Empire to take possession of the two Romanian principalities, Moldova and Wallachia, which had been requested from the very beginning of the confrontation, the war ended with a cession of the Moldavian territory of the left side of the Prut in favor of the Russian Empire. At the same time, Russia for the first time in history gained access to the Danube, or more precisely to the lower reaches of this river, which had a great economic potential of international importance. Thus, the portion of this river, beginning from the point where Prut joins Danube and up to the confluence of the Chilia branch into the Black Sea, became a part of the Russian border along the Bessarabian segment. During the 19th century, this part of the border was subject to a number of changes. In 1829, after the end of the next Russian-Turkish war the border was established along the Sfantu Gheorghe stream (the southern branch). Thus, all the Danube branches were under the control of Russia, which created, both directly and indirectly, many obstacles to the free and safe navigation of foreign commercial vessels in the lower reaches of the river. This fact was the cause of concern and discontent of Western European states that took advantage of the right moment, namely, the signing of the Treaty of Paris in 1856 after the Crimean War, when Russia found itself in an unfavorable situation and was forced to cede the territory of the south of Bessarabia to Moldova. At the same time the movement of the border line to the north of the Lower Danube section guaranteed compliance with the international navigation regime, which was established throughout the Danube river course, including the delta. The border on the Bessarabia segment was again modified at the Berlin Congress of 1878, when the Russian Empire returned the respective territories lost in 1856. This fact has become one of the main conditions for the international recognition of the independence of Romania. But still the border on the Bessarabian segment was not restored along the Sfantu Gheorghe stream, but ran along the Chilia branch. Thus, the border along the Bessarabia was systematically modified due to the main European actors' interests in the navigation on the Lower Danube and changes in the international conjuncture in different periods of the 19th century.