Bulgaria (1879: Agreement)

 Bulgaria (Bulgarian: България, officially the Kingdom of Bulgaria (Царство България, Tsartsvo Bulgaria), is a country in Southern Europe. Bulgaria borders four other countries: Romania and Serbia to the north (mostly along the Danube), Albania to the west, and Greece to the south. The Black Sea defines the extent of the country to the east.

Several mountainous areas define the landscape, most notably the Stara Planina (Balkan) and Rodopi mountain ranges, as well as the Rila range, which includes the highest peak in the Balkan region, Musala. In contrast, the Danubian plain in the north and the Upper Thracian Plain in the south represent Bulgaria's lowest and most fertile regions. The 378-kilometer (235 mi) Black Sea coastline covers the entire eastern bound of the country. Bulgaria's capital city and largest settlement is Sofia, with a permanent population of 878,000 people.

The emergence of a unified Bulgarian ethnicity and state dates back to the 7th century AD. All Bulgarian political entities that subsequently emerged preserved the traditions (in ethnic name, language and alphabet) of the First Bulgarian Empire (681–1018), which at times covered most of the Balkans and eventually became a cultural hub for the Slavs in the Middle Ages. With the decline of the Second Bulgarian Empire (1185–1396/1422), Bulgarian territories came under Ottoman rule for nearly five centuries. The Russo-Turkish War of 1877–1878 led to the establishment of a Third Bulgarian state in 1878.