The convention of Sofia between

Bulgaria Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is situated on the eastern portion of the Balkans directly south of the Danube river and west of the Black Sea. Bulgaria is bordered by Greece and Turkey t ...

and the

Ottoman Empire The Ottoman Empire (), also called the Turkish Empire, was an empire, imperial realm that controlled much of Southeast Europe, West Asia, and North Africa from the 14th to early 20th centuries; it also controlled parts of southeastern Centr ...

(Turkey) was signed on 6 September (24 August O.S.) 1915. It rectified the border between the two countries in Bulgaria's favour in order to bring Bulgaria into the

First World War World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

on the side of the

Central Powers The Central Powers, also known as the Central Empires,; ; , ; were one of the two main coalitions that fought in World War I (1914–1918). It consisted of the German Empire, Austria-Hungary, the Ottoman Empire, and the Kingdom of Bulga ...

. A defensive alliance between Bulgaria and Turkey had been concluded on 19 August 1914, but negotiations for Bulgaria's intervention in the war did not begin between the two parties until May 1915. It quickly became clear that Bulgaria sought a rectification of the border, and

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

and

Austria-Hungary Austria-Hungary, also referred to as the Austro-Hungarian Empire, the Dual Monarchy or the Habsburg Monarchy, was a multi-national constitutional monarchy in Central Europe#Before World War I, Central Europe between 1867 and 1918. A military ...

put pressure on their Ottoman ally to accept. The Austro-Hungarians for their part were convinced that a Turco-Bulgarian alliance would keep

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

and

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

neutral. The German ambassador to Turkey, Hans von Wangenheim, was unconvinced by the proposed alliance, believing that Romanian neutrality could only be secured by Austro-Hungarian territorial concessions. The Austro-Hungarian ambassador, Johann von Pallavicini, convinced the Ottomans to accept a border rectification, but Bulgaria initially refused to consider abandoning their neutrality—the only condition on which the Ottomans would yield territory. On 6 August 1915, the British launched an offensive on Gallipoli that exposed Turkey's grave shortage of munitions. On 17 August, the Turkish minister of war,

Enver Pasha İsmâil Enver (; ; 23 November 1881 – 4 August 1922), better known as Enver Pasha, was an Ottoman Empire, Ottoman Turkish people, Turkish military officer, revolutionary, and Istanbul trials of 1919–1920, convicted war criminal who was a p ...

, wrote to the German chief of staff,

Erich von Falkenhayn Erich Georg Sebastian Anton von Falkenhayn (11 September 1861 – 8 April 1922) was a German general and Ottoman Field Marshal who served as Prussian Minister of War and Chief of the German General Staff during the First World War. Falkenha ...

, to see if an Austro-German offensive against

Serbia , image_flag = Flag of Serbia.svg , national_motto = , image_coat = Coat of arms of Serbia.svg , national_anthem = () , image_map = , map_caption = Location of Serbia (gree ...

was forthcoming. When told that it hinged on Bulgaria's intervention, which in turn hinged on a Turco-Bulgarian pact, the Ottomans reached a quick agreement with Bulgaria on 22 August. They ceded the

Maritsa Maritsa or Maritza ( ), also known as Evros ( ) and Meriç ( ), is a river that runs through the Balkans in Southeast Europe. With a length of ,

river and its left bank to a depth of 1.5 kilometres. This gave Bulgaria control of the railway to the Aegean port of

Dedeagach Alexandroupolis (, ) or Alexandroupoli (, ) is a city in Greece and the capital of the Evros regional unit. It is the largest city in Greek Thrace and the region of Eastern Macedonia and Thrace, with a population of 71,751, and is an importan ...

. It also left

Edirne Edirne (; ), historically known as Orestias, Adrianople, is a city in Turkey, in the northwestern part of the Edirne Province, province of Edirne in Eastern Thrace. Situated from the Greek and from the Bulgarian borders, Edirne was the second c ...

(Adrianople) vulnerable to Bulgarian attack, but signature of the accord was dependent on a military convention being signed between Bulgaria, Austria-Hungary and Germany. In addition to the Bulgarian-Ottoman convention, Bulgaria also signed a treaty of alliance with Germany and a military convention between Germany, Austria-Hungary and Bulgaria in

Sofia Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

on 6 September. Bulgaria agreed to allow the transit of German and Austro-Hungarian supplies through its territory to the Ottoman Empire and to invade Serbia with a large force. By November, Turkey's critical supply problem, which had threatened to destroy the regime in August, had been resolved.

Notes

Sources

* * * {{DEFAULTSORT:Bulgarian-Ottoman convention (1915) World War I treaties Bulgaria in World War I Ottoman Empire in World War I Treaties concluded in 1915 Military alliances involving Bulgaria Military alliances involving the Ottoman Empire Bulgaria–Ottoman Empire relations 1915 establishments in Bulgaria 1915 establishments in the Ottoman Empire 1918 disestablishments in Bulgaria 1918 disestablishments in the Ottoman Empire 20th-century military alliances September 1915 History of Western Thrace Maritsa