Slavs in the context of "Operation Barbarossa"

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 to the south, Serbia and North Macedonia to the west, and Romania to the north. It covers a territory of 110,994 square kilometres (42,855 sq mi) and is the tenth largest within the European Union and the sixteenth-largest country in Europe by area. Sofia is the nation's capital and largest city; other major cities include Burgas, Plovdiv, and Varna.

One of the earliest societies in the lands of modern-day Bulgaria was the Karanovo culture (6,500 BC). In the 6th to 3rd century BC, the region was a battleground for ancient Thracians, Persians, Celts, and Macedonians; stability came when the Roman Empire conquered the region in AD 45. After the Roman state splintered, tribal invasions in the region resumed. Around the 6th century, these territories were settled by the early Slavs. The Bulgars, led by Asparuh, attacked from the lands of Old Great Bulgaria and permanently invaded the Balkans in the late 7th century. They established the First Bulgarian Empire, victoriously recognised by treaty in 681 AD by the Byzantine Empire. It dominated most of the Balkans and significantly influenced Slavic cultures by developing the Cyrillic script. Under the rule of the Krum's dynasty, the country rose to the status of a mighty empire and great power. The First Bulgarian Empire lasted until the early 11th century, when Byzantine emperor Basil II conquered and dismantled it. A successful Bulgarian revolt in 1185 established a Second Bulgarian Empire, which reached its apex under Ivan Asen II (1218–1241). After numerous exhausting wars and feudal strife, the empire disintegrated and in 1396 fell under Ottoman rule for nearly five centuries.

Serbia, officially the Republic of Serbia, is a landlocked country in Southeast and Central Europe. Located in the Balkans, it borders Hungary to the north, Romania to the northeast, Bulgaria to the southeast, North Macedonia to the south, Croatia to the northwest, Bosnia and Herzegovina to the west, and Montenegro to the southwest. Serbia also claims to share a border with Albania through the disputed territory of Kosovo. Serbia has about 6.6 million inhabitants, excluding Kosovo. Serbia's capital, Belgrade, is also the largest city in the country.

Continuously inhabited since the Paleolithic age, the territory of modern-day Serbia faced Slavic migrations in the 6th century. Several regional states were founded in the Early Middle Ages and were at times recognised as tributaries to the Byzantine, Frankish and Hungarian kingdoms. The Serbian Kingdom obtained recognition by the Holy See and Constantinople in 1217, reaching its territorial apex in 1346 as the Serbian Empire. By the mid-16th century, the Ottoman Empire annexed the entirety of modern-day Serbia; their rule was at times interrupted by the Habsburg Empire, which began expanding towards Central Serbia from the end of the 17th century while maintaining a foothold in Vojvodina. In the early 19th century, the Serbian Revolution established the nation-state as the region's first constitutional monarchy, which subsequently expanded its territory.

South Slavs are Slavic people who speak South Slavic languages and inhabit a contiguous region of Southeast Europe comprising the eastern Alps and the Balkan Peninsula. Geographically separated from the West Slavs and East Slavs by Austria, Hungary, Romania, and the Black Sea, the South Slavs today include Bosniaks, Bulgarians, Croats, Macedonians, Montenegrins, Serbs and Slovenes.

In the 20th century, the country of Yugoslavia (from Serbo-Croatian, literally meaning "South Slavia" or "South Slavdom") united a majority of the South Slavic peoples and lands—with the exception of Bulgarians and Bulgaria—into a single state. The Pan-Slavic concept of Yugoslavia emerged in late 17th-century Croatia, at the time part of the Habsburg monarchy, and gained prominence through the 19th-century Illyrian movement. The Kingdom of Serbs, Croats and Slovenes, renamed the Kingdom of Yugoslavia in 1929, was proclaimed on 1 December 1918, following the unification of the State of Slovenes, Croats and Serbs with the kingdoms of Serbia and Montenegro. With the breakup of Yugoslavia in the early 1990s, several independent sovereign states were formed.

The early Slavs were an Indo-European peoples and speakers of the Indo-European dialectswho lived during the Migration Period and the Early Middle Ages (approximately from the 5th to the 10th centuries AD) in Central, Eastern and Southeast Europe and established the foundations for the Slavic nations through the Slavic states of the Early and High Middle Ages. The Slavs' original homeland is still a matter of debate due to a lack of historical records; however, scholars generally place it in Eastern Europe, with Polesia being the most commonly accepted location.

It is generally agreed that ancient Roman writers referred to the ancestors of Slavs as Venedi. The proto-Slavic term Slav shares roots with Slavic terms for speech, word, and perhaps was used by early Slavic people themselves to denote other people, who spoke languages similar to theirs. The first written use of the name "Slavs" dates to the 6th century, when the Slavic tribes inhabited a large portion of Central and Eastern Europe. By then, the nomadic Iranian-speaking peoples living in the European Pontic Steppe (the Scythians, Sarmatians, Alans, etc.) had been absorbed by the region's Slavic-speaking population. Over the next two centuries, the Slavs expanded westwards (to the Elbe river and in the Alps), and southwards (into the Balkans, absorbing Illyrian and Thracian peoples in the process), and also moved eastwards (in the direction of the Volga River). Between the sixth and seventh centuries, large parts of Europe came to be controlled or occupied by Slavs, a process less understood and documented than that of the Germanic ethnogenesis in the west. Yet the effects of Slavicization were far more profound.

The Balkan Wars were two conflicts that took place in the Balkan states in 1912 and 1913. In the First Balkan War, the four Balkan states of Greece, Serbia, Montenegro and Bulgaria declared war upon the Ottoman Empire and defeated it, in the process stripping the Ottomans of their European provinces, leaving only Eastern Thrace under Ottoman control. In the Second Balkan War, Bulgaria fought against the other four combatants of the first war. It also faced an attack from Romania from the north. The Ottoman Empire lost the bulk of its territory in Europe. Although not involved as a combatant, Austria-Hungary became relatively weaker as a much enlarged Serbia pushed for union of the South Slavic peoples. The war set the stage for the July crisis of 1914 and as a prelude to the First World War.

By the early 20th century, Bulgaria, Greece, Montenegro and Serbia had achieved independence from the Ottoman Empire, but large elements of their ethnic populations remained under Ottoman rule. Over the course of the Macedonian Struggle these states fought for influence between themselves and the Ottoman government within Ottoman Macedonia, during which their governments came under the control of nationalists. In 1912, these countries united to formed the Balkan League. The First Balkan War began on 8 October 1912, when the League member states attacked the Ottoman Empire, and ended eight months later with the signing on 30 May 1913 of the Treaty of London negotiated together with the Great Powers. The Great Powers - particularly Italy and Austria-Hungary -- included independence for Albania in the Treaty. The Second Balkan War began on 16 June 1913, when Bulgaria, dissatisfied with its allotment of territory from Macedonia, attacked its former Balkan League allies. The combined forces of the Serbian and Greek armies, with their superior numbers repelled the Bulgarian offensive and counter-attacked by invading Bulgaria from the west and the south. Romania, having taken no part in the first conflict, had intact armies to strike with and invaded Bulgaria from the north in violation of a peace treaty between the two states. The Ottoman Empire also attacked Bulgaria and advanced in Thrace, regaining Adrianople. In the resulting Treaty of Bucharest, Bulgaria managed to retain most of the territories it had gained in the First Balkan War. However, it was forced to cede the ex-Ottoman south part of Dobruja province to Romania.

Sofia is the capital and 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 Iskar river and has many mineral springs, such as the Sofia Central Mineral Baths. It has a humid continental climate.

Known as Serdica in antiquity, Sofia has been an area of human habitation since at least 7000 BC. The recorded history of the city begins with the attestation of the conquest of Serdica by the Roman Republic in 29 BC from the Celtic tribe Serdi. During the decline of the Roman Empire, the city was raided by Huns, Visigoths, Avars, and Slavs. In 809, Serdica was incorporated into the First Bulgarian Empire by Khan Krum and became known as Sredets. In 1018, the Byzantines ended Bulgarian rule until 1194, when it was reincorporated by the Second Bulgarian Empire. Sredets became a major administrative, economic, cultural and literary hub until its conquest by the Ottomans in 1382. From 1530 to 1836, Sofia was the regional capital of Rumelia Eyalet, the Ottoman Empire's largest and most important province. Bulgarian rule was restored in 1878. Sofia was selected as the capital of the Third Bulgarian State in the next year, ushering a period of intense demographic and economic growth.

The Ecumenical Patriarch of Constantinople (Greek: Οἰκουμενικός Πατριάρχης, romanized: Oikoumenikós Patriárchēs) is the archbishop of Constantinople and primus inter pares (first among equals) among the heads of the several autocephalous churches that comprise the Eastern Orthodox Church. The ecumenical patriarch is regarded as the representative and spiritual leader of the Eastern Orthodox Christians worldwide. The term ecumenical in the title is a historical reference to the Ecumene, a Greek designation for the civilised world, i.e. the Roman Empire, and it stems from Canon 28 of the Council of Chalcedon.

The patriarch's see, the Ecumenical Patriarchate of Constantinople, is one of the most enduring institutions in the world and has had a prominent part in world history. The ecumenical patriarchs in ancient times helped in the spread of Christianity and the resolution of various doctrinal disputes. In the Middle Ages, they played a major role in the affairs of the Eastern Orthodox Church, as well as in the politics of the Orthodox world, and in spreading Christianity among the Slavs. Currently, in addition to the expansion of the Christian faith and the Eastern Orthodox doctrine, the patriarchs are involved in ecumenism and interfaith dialogue, charitable work, and the defense of Orthodox Christian traditions.

Eastern Europe is a subregion of the European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural and socio-economic connotations. Its eastern boundary is marked by the Ural Mountains, and its western boundary is defined in various ways. Narrow definitions, in which Central and Southeast Europe are counted as separate regions, include Belarus, Russia and Ukraine. In contrast, broader definitions include Moldova and Romania, but also some or all of the Balkans, the Baltic states, the Caucasus, and the Visegrád group. In Eastern Europe, Russia is the largest and most populous country.

The region represents a significant part of European culture; the main socio-cultural characteristics of Eastern Europe have historically largely been defined by the traditions of the Slavs, as well as by the influence of Eastern Christianity as it developed through the Eastern Roman Empire and the Ottoman Empire. Another definition was created by the Cold War, as Europe was ideologically divided by the Iron Curtain, with "Eastern Europe" being synonymous with communist states constituting the Eastern Bloc under the influence of the Soviet Union.