The Principality of Romania gained Northern Dobruja (including the Danube Delta and the Snake Island) in 1878 after defeating the Ottoman Empire together with Russia in the Russo-Turkish War of 1877–1878. This territory was given by Russia as an "exchange" or "compensation" for the annexation by the latter of the Romanian region of Southern Bessarabia. Romania later conquered Southern Dobruja as well in 1913 after a war against Bulgaria, then lost the whole Dobruja (except for the Danube Delta) during World War I after the Treaty of Bucharest of 1918, regained it a year later after the Treaty of Neuilly-sur-Seine, and eventually lost Southern Dobruja after the Treaty of Craiova on 7 September 1940, this being followed by a population exchange with Bulgaria.