Ostsiedlung in the context of "Lower Silesia"

Prussia (/ˈprʌʃə/; German: Preußen [ˈpʁɔʏsn̩] ; Old Prussian: Prūsija) was a German state centred on the North European Plain that originated from the 1525 secularization act of the Prussian part of the State of the Teutonic Order. For centuries, the House of Hohenzollern ruled Prussia, expanding its size with the Prussian Army. Prussia, with its capital at Königsberg and then, when it became the Kingdom of Prussia in 1701, Berlin, decisively shaped the history of Germany. Prussia formed the German Empire when it united the German states in 1871. It was de facto dissolved by an emergency decree transferring powers of the Prussian government to German Chancellor Franz von Papen in 1932 and de jure by an Allied decree in 1947.

The name Prussia derives from the Old Prussians who were conquered by the Teutonic Knights – an organized Catholic medieval military order of German crusaders – in the 13th century. In 1308, the Teutonic Knights conquered the region of Pomerelia with Danzig. Their monastic state was mostly Germanised through immigration from central and western Germany, and, in the south, it was Polonised by settlers from Masovia. The imposed Second Peace of Thorn (1466) split Prussia into the western Royal Prussia, a province of Poland, and the eastern Duchy of Prussia, a feudal fief of the Crown of Poland until 1657. After 1525, the Teutonic Order relocated their headquarters to Mergentheim, but managed to keep land in Livonia until 1561. The union of Brandenburg and the Duchy of Prussia in 1618 led to the proclamation of the Kingdom of Prussia in 1701.

East Prussia (German: Ostpreußen [ˈɔstˌpʁɔɪ̯sn̩] ) was a province of the Kingdom of Prussia from 1772 to 1829 and again from 1878 (with the Kingdom itself being part of the German Empire from 1871); following World War I it formed part of the Weimar Republic's Free State of Prussia, until 1945. Its capital city was Königsberg (present-day Kaliningrad). East Prussia was the main part of the region of Prussia along the southeastern Baltic Coast.

The bulk of the ancestral lands of the Baltic Old Prussians were enclosed within the later province of East Prussia. During the 13th century, the native Prussians were conquered by the crusading Teutonic Knights. After the conquest they were gradually converted to Christianity. As a result of the medieval Ostsiedlung, Germans became the dominant ethnic group, while Poles and Lithuanians formed sizeable minorities. From the 13th century, the region of Prussia was part of the monastic state of the Teutonic Knights. After the Second Peace of Thorn in 1466 it became a part of the Kingdom of Poland, either directly (Warmia) or as a fief (remainder). In 1525, with the Prussian Homage, the territory became the Duchy of Prussia, a vassal duchy of Poland. It gained full sovereignty in 1657, when Poland renounced its feudal rights in the Treaty of Bromberg.

German Bohemians (German: Deutschböhmen und Deutschmährer [ˈdɔʏtʃˌbøːmən] ; Czech: čeští Němci a moravští Němci, lit. 'German Bohemians and German Moravians'), later known as Sudeten Germans (German: Sudetendeutsche [zuˈdeːtn̩ˌdɔʏtʃə] ; Czech: sudetští Němci), were ethnic Germans living in the Czech lands of the Bohemian Crown, which later became an integral part of Czechoslovakia. Before 1945, over three million German Bohemians constituted about 23% of the population of the whole country and about 29.5% of the population of Bohemia and Moravia. Ethnic Germans migrated into the Kingdom of Bohemia, an electoral territory of the Holy Roman Empire, from the 11th century, mostly in the border regions of what was later called the "Sudetenland", which was named after the Sudeten Mountains.

The process of German expansion was known as Ostsiedlung ("Settling of the East"). The name "Sudeten Germans" was adopted during rising nationalism after the fall of Austria-Hungary in the aftermath of First World War. After the Munich Agreement (1938), the so-called Sudetenland became part of Germany.

The Junkers (/ˈjʊŋkər/ YUUNG-kər; German: [ˈjʊŋkɐ]) were members of the landed nobility in Prussia. They owned great estates that were maintained and worked by peasants with few rights.‍ These estates often lay in the countryside outside of major cities or towns. They were an important factor in Prussian and, after 1871, German military, political and diplomatic leadership. One of the most famous Junkers was Chancellor Otto von Bismarck.‍ Bismarck held power in Germany from 1871 to 1890 as Chancellor of the German Empire; he was dismissed by Kaiser Wilhelm II.‍

Many Junkers lived in the eastern provinces that were annexed by either Poland or the Soviet Union after World War II. Junkers fled or were expelled alongside other German-speaking populations by the incoming Polish and Soviet administrations, and their lands were confiscated. In western and southern Germany, the land was often owned by small independent farmers or a mixture of small farmers and estate owners, and this system was often contrasted with the dominance of the large estate owners of the east. Before World War II, the dividing line was often drawn at the river Elbe, which was also roughly the western boundary of Slavic settlement by the Wends in the so-called Germania Slavica prior to Ostsiedlung. The term for the Junker-dominated East was thus Ostelbien, or 'East Elbia'. They played a prominent role in repressing the liberal movement in Germany, and were often described as reactionary.