Bulgaria–Türkiye border

Drawn in the Balkan Wars

The US Geographer described this border, like the Greece–Türkiye one, as part of a long contest for the land bridge between Europe and Asia at the Straits.^[1] The Ottomans took Adrianople (Edirne) in 1361 and made it their capital, and Bulgaria stayed under Ottoman rule for about five centuries.^[1]

The Treaty of Berlin in 1878 created a small Bulgarian state between the Balkan Mountains and the Danube, still subject to the Sultan. Prince Ferdinand declared Bulgaria independent in 1908.^[1]

In October 1912 Bulgaria, Serbia, Greece and Montenegro went to war with the Ottoman Empire. Bulgarian troops took Kırklareli and, in March 1913, Adrianople itself.^[1] The Treaty of London of 30 May 1913 made Turkey give up everything west of a line from Enos (Enez) on the Aegean to Midia (Midye) on the Black Sea.^[1]

The allies then fell out. In the Second Balkan War of 1913, Turkey joined Bulgaria's enemies and easily took Adrianople back.^[1] The Treaty of Constantinople, signed on 29 September 1913, moved the border west to the Maritsa, and Bulgaria lost Adrianople.^[1]

“The frontier between the two countries commences at the mouth of the river Rezvaja, south of the Monastery of San Ivan, which is located on the Black Sea; it follows the course of this river as far as the confluence of the rivers Pirogu and Deliva, to the west of Kamila-Koj.”^[1]

A price for an alliance

In October 1915 Bulgaria entered the First World War on the side of Turkey and the Central Powers.^[1] The decision was made easier by the Convention of Sofia, signed on 6 September 1915, in which Turkey handed over the land around Uskudar (Shtit) and moved the rest of the 1913 line to about a mile east of the Maritsa.^[1]

Bulgaria lost the war. The Treaty of Neuilly of 27 November 1919 cut it off from the Aegean but kept this border as set in 1913 and 1915, and set up an international commission to mark it.^[1] That commission demarcated the whole line in 1921. The Treaty of Lausanne of 24 July 1923 confirmed it, and in 1926 another commission fixed the tripoint with Greece on the Maritsa.^[1] The 1947 Paris peace treaty confirmed Bulgaria's borders as they stood on 1 January 1941.^[1]

From the Black Sea to the Maritsa

The line starts at the mouth of the Rezovska on the Black Sea and follows it for 66 km, then the Deliva for another 15 km. It crosses ridges, follows the Golema stream briefly, and runs 95.5 km over land to the Tundzha. It then follows the Tundzha south for 12 km, and runs on to the Kalamitsa and a last straight line to the Maritsa.^[1] In 1965 the US Geographer counted 320 pillars on the land sections and reported no active disputes over the line, though it said the possibility of friction remained.^[1]

Most of it crosses the Istranca hills, which are covered in oak, beech and some pine, or in scrub that is hard to get through. In 1965 only one all-weather road crossed the border in these hills, linking Kırklareli in Turkey with Malko Turnovo in Bulgaria.^[1] The main route from central Europe to Istanbul crosses much further west, near Edirne and the Greek tripoint.^[1]

At the eastern end, a 1997 agreement put the border in the Rezovska's mouth on the median line of the river bed and had the two countries clear the channel so the river could flow freely into the sea. It also drew the line through Rezovo Bay and out across the Black Sea, leaving its far northeastern end for later talks.^[2]

People on the move

The border has seen large movements of people. When the First Balkan War broke out, most Bulgarians were driven out of Eastern Thrace, while Turks, Pomaks and other Muslims moved in from Bulgaria and other former Ottoman lands.^[1] The US Geographer reported that in 1950 Bulgaria expelled 250,000 Turks, nearly a third of its Turkish population.^[1]

Between 24 December 1984 and 14 January 1985, Bulgaria's communist government changed the names of 310,000 people to Bulgarian ones, mostly in areas with large Turkish populations. Protests in May 1989 ended in violent clashes with police.^[4] On 29 May 1989, leader Todor Zhivkov announced on television that the border with Turkey would open, and Turkey opened its side on 3 June.^[4] By 21 August about 360,000 people had left on three-month tourist visas, which is why it was called the “Big Excursion”. By the end of 1990, 150,000 had gone back to Bulgaria.^[4]

Fence and freight

More than 10,000 refugees, mostly Syrians, crossed into Bulgaria in 2013. In January 2014 Bulgaria began a three-metre barbed-wire fence along the border and had largely finished its first 33 km by July.^[5] By 2016 it had built 200 km of razor-wire fence, and it planned another 24 km for 2017.^[6]

The same border carries heavy traffic. Kapitan Andreevo–Kapıkule was Türkiye's busiest border crossing for passenger traffic in the first half of 2022, with about 1.226 million vehicles.^[3]