The presence of German-speaking populations in Central and Eastern Europe is rooted in centuries of history, with the settling in northeastern Europe of Germanic peoples predating even the founding of the Roman Empire. The presence of independent German states in the region (particularly Prussia), and later the German Empire as well as other multi-ethnic countries with German-speaking minorities, such as Hungary, Poland, Imperial Russia, etc., demonstrates the extent and duration of German-speaking settlements. The number of ethnic Germans in Central and Eastern Europe dropped dramatically as the result of the post-1944 German flight and expulsion from Central and Eastern Europe. There are still substantial numbers of ethnic Germans in the countries that are now Germany and Austria's neighbors to the east—Poland, Czechia, Slovakia, and Hungary. Finland, the Baltics (Estonia, Latvia, Lithuania), the Balkans (Slovenia, Croatia, Bosnia, Serbia, Romania, Bulgaria, Turkey) and the former Soviet Union (Moldova, Ukraine, Russia, Georgia, Armenia, Azerbaijan) also have smaller but still significant numbers of citizens of German descent. Early Middle Ages settlement area During the 4th and 5th centuries, in what is known as the Migration Period, Germanic peoples (ancient Germans) seized control of the decaying Western Roman Empire in the South and established new kingdoms within it. Meanwhile, formerly Germanic areas in Eastern Europe and present-day Eastern Germany, were settled by Slavs. In the early Middle Ages, Charlemagne had subdued a variety of Germanic peoples in Central Europe dwelling in an area roughly bordered by the Alps in the South, the Vosges Mountains in the West, the North Sea and Elbe River in the North and the Saale River in the East. These inhomogeneous Germanic peoples comprised several tribes and groups who either formed, stayed or migrated into this area during the Migration Period. After the Carolingian Empire was divided, these people found themselves in the eastern part, known as East Francia or Regnum Teutonicum, and over time became known as Germans. The area was divided into the stem duchies of Swabia (Alamannia), Franconia, Saxony, and Bavaria (including Carinthia). Later, the Holy Roman Empire would be constituted largely, but not exclusively of these regions. Medieval settlements (Ostsiedlung) The medieval German Ostsiedlung (literally Settling eastwards), also known as the German eastward expansion or East colonization refers to the expansion of German culture, language, states, and settlements to vast regions of Northeastern, Central and Eastern Europe, previously inhabited since the Great Migrations by Balts, Romanians, Hungarians