Silistra Province in the context of "Silistra"

Southern Dobruja or South Dobruja (Bulgarian: Южна Добруджа, romanized: Yuzhna Dobrudzha or simply Добруджа, Dobrudzha; Romanian: Dobrogea de Sud or Dobrogea Nouă, lit. 'New Dobruja'), also the Quadrilateral (Romanian: Cadrilater), is an area of north-eastern Bulgaria comprising Dobrich and Silistra provinces, part of the historical region of Dobruja. It has an area of 7,412 square km and a population of 358,000.

It is historically noteworthy as a point of contention in Bulgarian-Romanian relations. Part of Bulgaria between 1878 and 1913, the region was annexed by Romania in the Treaty of Bucharest (1913), targeted by Bulgaria during World War I (1914–18), and subsequently remained Romanian until 1940, when Bulgaria regained control in the Treaty of Craiova, which went along with a compulsory population exchange. Southern Dobruja has been part of Bulgaria since 1940.

Dulovo (Bulgarian: Дулово [ˈduɫovo], Turkish: Akkadınlar, lit. "White women"; Romanian: Accadânlar) is a town in Silistra Province in northeastern Bulgaria, in the Ludogorie region. As the administrative centre of the homonymous Dulovo Municipality, it is the third largest town in the province after Silistra and Tutrakan. As of December 2009, the town had a population of 6,621.

Dulovo, then a village, was first mentioned in an Ottoman document of 1573 as "Akkadınlar", meaning "White Women". Even before the Liberation of Bulgaria in 1878, it had a mixed population of Bulgarians (settlers from the region of Preslav) and Turks, which is still reflected in the ethnic composition today. Following the Second Balkan War, Bulgaria was forced to cede it to Romania along with all of Southern Dobruja. It was also a district centre of Durostor County under Romanian rule. The village was given back to Bulgaria according to the Treaty of Craiova of 1940. In 1942, it acquired its present name (in honour of the early medieval Bulgarian Dulo clan, with the Bulgarian placename suffix –ovo). On 30 January 1960, Dulovo was granted town status.

Bulgarian Turks (Bulgarian: български турци; Turkish: Bulgaristan Türkleri) are ethnic Turkish people from Bulgaria. According to the 2021 census, there were 508,375 Bulgarians of Turkish descent, roughly 8.4% of the population, making them the country's largest ethnic minority. Bulgarian Turks also comprise the largest single population of Turks in the Balkans. They primarily live in the southern province of Kardzhali and the northeastern provinces of Shumen, Silistra, Razgrad and Targovishte. There is also a diaspora outside Bulgaria in countries such as Turkey, Austria, the Netherlands, Sweden, Norway and Romania, the most significant of which are the Bulgarian Turks in Turkey.

Bulgarian Turks are the descendants of Turkish settlers who entered the region after the Ottoman conquest of the Balkans in the late 14th and early 15th centuries, as well as Bulgarian converts to Islam who became Turkified during the centuries of Ottoman rule. However, it has also been suggested that some Turks living today in Bulgaria may be direct ethnic descendants of earlier medieval Pecheneg, Oghuz, and Cuman Turkic tribes. According to local tradition, following a resettlement policy Karamanid Turks (mainly from the Konya Vilayet, Nevşehir Vilayet and Niğde Vilayet of the Karaman Province) were settled mainly in the Kardzhali area by the sultans Mehmed the Conqueror, Selim and Mahmud II. The Turkish community became an ethnic minority when the Principality of Bulgaria was established after the Russo-Turkish War of 1877–78. This community is of Turkish ethnic consciousness and differs from the majority Bulgarian ethnicity and the rest of the Bulgarian nation by its own language, religion, culture, customs, and traditions.

43°35′N 28°0′E / 43.583°N 28.000°E / 43.583; 28.000

Dobrich Province (Bulgarian: Област Добрич, Oblast Dobrich, former name Dobrich okrug) is a province in northeastern Bulgaria, part of Southern Dobruja geographical region. It is bounded on the east by the Black Sea, on the south by Varna Province, on the west by Shumen and Silistra provinces, and on the north by Romania. It is divided into eight municipalities. At the 2011 census, it had a population of 186,016.The province was part of Romania between 1913 and 1940.

Islam in Bulgaria is a minority religion and the second largest religion in the country after Christianity. According to the 2021 Census, the total number of Muslims in Bulgaria stood at 638,708 corresponding to 9.8% of the population. Ethnically, Muslims in Bulgaria are Turks, Bulgarians and Roma, living mainly in parts of northeastern Bulgaria (mainly in Razgrad, Targovishte, Shumen and Silistra Provinces) and in the Rhodope Mountains (mainly in Kardzhali Province and Smolyan Province).

Kaynardzha (also transliterated as Kajnardža; Bulgarian: Кайнарджа, IPA: [kɐjnɐrˈd͡ʒa]; Romanian: Cainargeaua Mică; Turkish: Kaynarca; Greek: Καϊναρτζή) is a village in northeastern Bulgaria, part of Silistra Province. It is the administrative centre of Kaynardzha Municipality, which lies in the easternmost part of Silistra Province, in the historical region of Southern Dobruja, close to the Romanian border.

The village is known as the location of the signing of the Treaty of Küçük Kaynarca on 21 July 1774 between Count Pyotr Rumyantsev, representative of Empress Catherine the Great of the Russian Empire and Musul Zade Mehmed Pasha, representative of Sultan Abdul Hamid I of the Ottoman Empire. The treaty put an end to the Russo-Turkish War of 1768–1774, which was devastating for the once-mighty Ottoman realm.

Dulovo Municipality (Bulgarian: Община Дулово) is a municipality (obshtina) in Silistra Province, Northeastern Bulgaria, located in the Danubian Plain, in the area of the South Dobrudzha geographical region, about 25 km south of Danube river. It is named after its administrative centre – the town of Dulovo.

The municipality embraces a territory of 566.33 km with a population of 28,860 inhabitants, as of December 2009.