Treaty of Neuilly-sur-Seine

Bulgaria entered the First World War on the side of the Central Powers and signed an armistice on 29 September 1918. The peace treaty was negotiated as part of the Paris Peace Conference settlement. Bulgaria and representatives of the Allied and Associated Powers signed it at Neuilly-sur-Seine, near Paris, on 27 November 1919. The treaty entered into force on 9 August 1920. It is also called the Treaty of Neuilly or the Neuilly Peace Treaty; its formal title was the Treaty of Peace between the Allied and Associated Powers and Bulgaria.

The treaty fixed Bulgaria’s postwar frontiers and required it to cede territory. Bulgaria transferred areas to the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia), while Western Thrace was ceded to the Allied and Associated Powers, which later transferred it to Greece. The loss of Western Thrace deprived Bulgaria of direct access to the Aegean Sea. These changes affected communities across the new borders and were among the settlement’s lasting political consequences.

The treaty limited Bulgaria’s regular army to 20,000 personnel and placed restrictions on its military equipment and armed forces. It also imposed reparations. Encyclopaedia Britannica reports that 75 percent of the reparations were later remitted; the obligation was therefore substantially reduced over time. The treaty further contained provisions on responsibility, property, prisoners, and the treatment of minorities, as well as the Covenant of the League of Nations.

The Neuilly treaty was one of several peace treaties concluded with the defeated Central Powers after the First World War. It was designed to settle relations between Bulgaria and the Allied states and to establish a postwar legal and political framework. The League covenant’s inclusion connected the agreement with the emerging League of Nations system. Historians have examined the territorial and financial terms in relation to postwar stability, Bulgarian politics, and the experience of people living in territories transferred across borders.