Treaty of Neuilly-sur-Seine
Historically a Bulgarian land, The Kingdom of Serbs, Croats and Slovenes gained some territory from Bulgaria as part of the Treaty of Neuilly-sur-Seine, following the invasion and occupation of part of the Kingdom of Serbia by Bulgaria and subsequent Allied defeat of the Central Powers in the First World War. From 1929 to 1941, it was part of Vardar Banovina. The Bulgarian army occupied Bosilegrad during the Second World War from 1941 to 1944. At the end of the Second World War, Bulgaria switched the sides in the war and in October 1944 gave the occupied Western outlands back to Yugoslavia.