Treaty of Neuilly-sur-Seine
The treaty required Bulgaria to cede Western Thrace to the Entente, (which ceded it to Greece at the San Remo conference) thereby cutting off its direct outlet to the Aegean Sea and an area of 2563 km² on the western border to the Kingdom of Serbs, Croats and Slovenes. The treaty also forced Bulgaria to return Southern Dobruja, which had been captured during the war and restored the border set by the Treaty of Bucharest (1913). Bulgaria was also required to reduce its army to 20,000 men, pay reparations of £100 million, and recognize the existence of the Kingdom of Serbs, Croats and Slovenes. The signing ceremony was held in Neuilly's town hall (hôtel de ville).
In Bulgaria, the results of the treaty are popularly known as the Second National Catastrophe. Bulgaria regained South Dobrudja as a result of the Treaty of Craiova and during World War II together with National Socialist Germany, temporarily reoccupied most of the other territories ceded by the treaty.
Territories ceded to the Kingdom of Serbs, Croats and Slovenes
Four minor regions (historiographically referred to as the Western Outlands by Bulgarians) had formed a part of Bulgaria (excluding the region around Strumitsa, which became part of Bulgaria in 1912) from its inception as a principality in 1878. Bulgaria became internationally recognised as an independent country in 1908 and controlled these territories until 1919 when they were ceded to the Kingdom of the Serbs, Croats and Slovenes (later renamed to the Kingdom of Yugoslavia) under the Treaty of Neuilly. The cession of the region was partly a compensation for the occupation of the southern and eastern part of Serbia by Bulgarian troops in the period between 1915 and 1918 and partly served strategic grounds. The old political boundary between Bulgaria and Serbia followed a chain of high mountain ridges, whereas the new one gave significant military and strategic advantages to the Serbs exposing dangerously the Bulgarian capital of Sofia and thus reducing significantly the military threat for eastern Serbia in case of a new Bulgarian invasion (see also Balkan Wars and World War I).
The Treaty of Neuilly was one in the series of treaties after World War I (like the Treaty of Versailles, Treaty of Saint-Germain, Treaty of Trianon, Treaty of Sèvres) which were meant to diminish the military and political strength of the defeated members of the Central Powers. As a result of this, some areas with absolute Bulgarian majority (such as Bosilegrad and a part of the Dimitrovgrad municipality) were ceded to Serbia (within the Kingdom of Serbs, Croats and Slovenes).
Bulgarian sources claim that the treaty was to last for twenty years and that all territories should have been returned to Bulgaria in 1939, but that was not specified in the treaty.
Region and population
In Serbia, to which the term generally applies in Bulgaria, the territory ceded is split between the modern Serbian District of Pirot (municipality of Dimitrovgrad and smaller parts of the municipalities of Pirot and Babušnica) and District of Pčinja (municipality of Bosilegrad and a small part of the municipality of Surdulica). It also includes a small section along the Timok River in the municipality and District of Zaječar, composed by eight localities (seven populated by Vlachs and one populated by Bulgarians).
In 1919, the area corresponded to the following parts of the Bulgarian okrugs: Kyustendil, 661 km², Tzaribrod 418 km², Tran 278 km², Kula 172 km² and Vidin 17 km². Bulgarian sources claim that the Bulgarian population made 95% of the population in Bosilegrad and 75% of the population in Tzaribrod at the time. In the Yugoslav census of 1931, all South Slavs were simply counted as Yugoslavs (Serbs, Croats, Slovenes, Bulgarians) so a comparison could not be made. According to the last Census in Serbia from 2002, Bulgarians made 50% and 71% of population in Dimitrovgrad and Bosilegrad respectively.