Pannonian Plain in the context of "Bačka"

The First Bulgarian Empire (Church Slavonic: блъгарьско цѣсарьствиѥ, romanized: blŭgarĭsko tsěsarǐstvije; Bulgarian: Първо българско царство) was a medieval state that existed in Southeastern Europe between the 7th and 11th centuries AD. It was founded in 680–681 after part of the Bulgars, led by Asparuh, moved south to the northeastern Balkans. There they secured Byzantine recognition of their right to settle south of the Danube by defeating – possibly with the help of local South Slavic tribes – the Byzantine army led by Constantine IV. During the 9th and 10th century, Bulgaria at the height of its power spread from the Danube Bend to the Black Sea and from the Dnieper River to the Adriatic Sea and became an important power in the region competing with the Byzantine Empire.

As the state solidified its position in the Balkans, it entered into a centuries-long interaction, sometimes friendly and sometimes hostile, with the Byzantine Empire. Bulgaria emerged as Byzantium's chief antagonist to its north, resulting in several wars. The two powers also enjoyed periods of peace and alliance, most notably during the Second Arab Siege of Constantinople, where the Bulgarian army broke the siege and destroyed the Arab army, thus preventing an Arab invasion of Southeastern Europe. Byzantium had a strong cultural influence on Bulgaria, which also led to the eventual adoption of Christianity in 864. After the disintegration of the Avar Khaganate, the country expanded its territory northwest to the Pannonian Plain. Later the Bulgarians confronted the advance of the Pechenegs and Cumans, and achieved a decisive victory over the Magyars, forcing them to establish themselves permanently in Pannonia.

Baranya or Baranja (Croatian: Baranja, pronounced [bǎraɲa]; Hungarian: Baranya, pronounced [ˈbɒrɒɲɒ]) is a geographical and historical region between the Danube and the Drava rivers located in the Pannonian Plain. Its territory is divided between Hungary and Croatia. In Hungary, the region is included in Baranya county, while in Croatia, it is part of Osijek-Baranja county.

Novi Sad (Serbian: Нови Сад, pronounced [nôʋiː sâːd] ; see below for other names) is the second largest city in Serbia and the administrative center of the autonomous province of Vojvodina. It is located in the southern portion of the Pannonian Plain on the border of the Bačka and Syrmia geographical regions, lying on the banks of the Danube river, and facing the northern slopes of Fruška Gora. According to the 2022 census, the population of Novi Sad city proper stands at 260,438, its contiguous urban area has 325,511 inhabitants, and the population of its administrative area totals 368,967 people.It is the fifth largest city on the Danube river and the largest that is not a national capital.

Novi Sad was founded in 1694, when Serb merchants formed a colony across the Danube from the Petrovaradin Fortress, a strategic Habsburg military post. In subsequent centuries, it became an important trading, manufacturing and cultural centre, and has historically been dubbed the Serbian Athens. The city was heavily devastated in the 1848 Revolution, but was subsequently rebuilt and restored. Today, along with the Serbian capital city of Belgrade, Novi Sad is an industrial and financial center important to the Serbian economy.

Illyricum /ɪˈlɪrɪkəm/ was a Roman province created by Augustus in 27 BC to secure the northeastern Adriatic frontier. It combined Upper Illyricum (Dalmatia) and Lower Illyricum (Pannonia) under a governor resident at Salona, administering coastal and Danubian territories across what are now Albania, Bosnia and Herzegovina, Croatia, Hungary, Kosovo, Montenegro, Serbia, and Slovenia. The province incorporated the rugged Dinaric Alps, the eastern Adriatic islands, and the fertile Pannonian Plain, bringing Roman civil and military institutions to long-established Illyrian, Celtic, and Hellenized communities.

The term Illyrians was used to describe the inhabitants of the area as far back as the late 6th century BC by Hecataeus of Miletus.

Syrmia (Serbian: Срем, romanized: Srem; Croatian: Srijem; Pannonian Rusyn: Срим, romanized: Srim) is a region of the southern Pannonian Plain, which lies between the Danube and Sava rivers. It is divided between Serbia and Croatia. Most of the region is flat, with the exception of the low Fruška Gora mountain stretching along the Danube in its northern part.

The Great Hungarian Plain (also known as Alföld or Great Alföld, Hungarian: Alföld [ˈɒlføld] or Nagy Alföld) is a plain occupying the majority of the modern territory of Hungary. It is the largest part of the wider Pannonian Plain (however, the Great Hungarian Plain was not part of the ancient Roman province Pannonia). Its territory significantly shrank due to its eastern and southern boundaries being adjusted by the new political borders created after World War I when the Treaty of Trianon was signed in 1920.

Slavonia (/sləˈvoʊniə/; Croatian: Slavonija) is, with Dalmatia, Croatia proper, and Istria, one of the four historical regions of Croatia. Located in the Pannonian Plain and taking up the east of the country, it roughly corresponds with five Croatian counties: Brod-Posavina, Osijek-Baranja, Požega-Slavonia, Virovitica-Podravina, and Vukovar-Syrmia, although the territory of the counties includes Baranya, and the definition of the western extent of Slavonia as a region varies. The counties cover 12,556 square kilometres (4,848 square miles) or 22.2% of Croatia, inhabited by 806,192—18.8% of Croatia's population. The largest city in the region is Osijek, followed by Slavonski Brod and Vinkovci.

Slavonia is located in the Pannonian Basin, largely bordered by the Danube, Drava, and Sava rivers. In the west, the region consists of the Sava and Drava valleys and the mountains surrounding the Požega Valley, and plains in the east. Slavonia enjoys a moderate continental climate with relatively low precipitation.

The Vienna Basin (German: Wiener Becken, Czech: Vídeňská pánev, Slovak: Viedenská kotlina, Hungarian: Bécsi-medence) is a geologically young tectonic burial basin and sedimentary basin in the seam area between the Alps, the Carpathians and the Pannonian Plain. Although it topographically separates the Alps from the Western Carpathians, it connects them geologically via corresponding rocks underground.