On 7 September 1940 Southern Dobruja was restored to Bulgaria under the Treaty of Craiova. The treaty was followed by a mandatory population exchange: about 110,000 Romanians (almost 95% of which settled there after 1913) were forced to leave Southern Dobruja, whereas 77,000 Bulgarians had to leave northern Dobruja. Only a few hundred Romanians and Aromanians are left in the region to this day.
http://en.wikipedia.org/wiki/Southern_Dobruja