 In 1856, the Treaty of Paris returned the south of Bessarabia to Moldavia, but in 1878, the Kingdom of Romania returned them to the Russian Empire as a result of the Treaty of Berlin.At the time of annexation, Moldavian population predominated in Bessarabia.The colonization of the region in the 19th century led to a large increase in the Russian, Ukrainian, Lipovan, and Cossack population in the region; this together with a large influx of Bulgarian immigrants increased the Slavic population to more than a fifth of the total population by 1920.