Former eastern territories of Germany in the context of Wrocław

The Allied Control Council (ACC) or Allied Control Authority (German: Alliierter Kontrollrat), also referred to as the Four Powers (Vier Mächte), was the governing body of the Allied occupation zones in Germany (1945–1949/1991) and Austria (1945–1955) following the end of World War II in Europe. Following the defeat of the Nazis, Germany (less its former eastern territories) and Austria were occupied as two different areas, both by the same four Allies. Both were later divided into four zones by the 1 August 1945 Potsdam Agreement. Its members (Four-Power Authorities) were the Soviet Union, the United Kingdom, the United States, and France. The organisation was based in Schöneberg, Berlin.

The council was convened to determine several plans for postwar Europe, including how to change borders and transfer populations in Central Europe. As the four powers had joined themselves into a condominium asserting supreme power in Germany, the Allied Control Council was constituted the sole legal sovereign authority for Germany as a whole, replacing the civil government of Germany under the Nazi Party. In 1948, the Soviets withdrew from the ACC due to its conflict with the western Allies, who then established the Allied High Commission. In 1949, two German states (West and East Germany) were founded.

The Potsdam Agreement (German: Potsdamer Abkommen) was the agreement among three of the Allies of World War II: the United Kingdom, the United States, and the Soviet Union after the war ended in Europe that was signed on 1 August 1945 and published the following day. A product of the Potsdam Conference, it concerned the military occupation and reconstruction of Germany, its border, and the entire European Theatre of War territory. It also addressed Germany's demilitarisation, reparations, the prosecution of war criminals and the mass expulsion of ethnic Germans from various parts of Europe. France was not invited to the conference but formally remained one of the powers occupying Germany.

Executed as a communiqué, the agreement was not a peace treaty according to international law, although it created accomplished facts. It was superseded by the Treaty on the Final Settlement with Respect to Germany signed on 12 September 1990.

From 1945 to 1990, the divided Germany began with the Berlin Declaration, marking the abolition of the German Reich and Allied-occupied period in Germany on 5 June 1945, and ended with the German reunification on 3 October 1990.

Following the collapse of the Third Reich in 1945 and its defeat in World War II, Germany was stripped of its territorial gains. Beyond that, more than a quarter of its old pre-war territory was annexed by communist Poland and the Soviet Union. The German populations of these areas were expelled to the west. Saarland was a French protectorate from 1947 to 1956 without the recognition of the "Four Powers", because the Soviet Union opposed it, making it a disputed territory.

The influx of refugees in Schleswig-Holstein after the Second World War was one of the biggest difficulties faced in Germany in the early post-war period. Per capita, the Province of Schleswig-Holstein of Prussia, later the state of Schleswig-Holstein, took in the second-most refugees and displaced persons from the former eastern territories of Germany between 1944 and 1947, second only to Mecklenburg-Vorpommern. This led to an economic and humanitarian crisis in the state throughout the late 1940s. The situation was only resolved in the 1950s as the Wirtschaftswunder (economic miracle) enabled physical reconstruction, raised living standards, and aided in integrating the hundreds of thousands of new residents.

Operation Vistula (Polish: Akcja Wisła; Ukrainian: Опера́ція «Ві́сла») was the codename for the 1947 forced resettlement of close to 150,000 Ukrainians, Rusyns, Boykos, and Lemkos from the southeastern provinces of postwar Poland to the Recovered Territories in the west of the country.The action was carried out by the Soviet-installed Polish communist authorities to remove material support to the Ukrainian Insurgent Army. The Ukrainian Insurgent Army continued its guerrilla activities until 1947 in Subcarpathian and Lublin Voivodeships with no hope for any peaceful resolution; Operation Vistula brought an end to the hostilities.

In a period of three months beginning on 28 April 1947 and with Soviet approval and aid about 141,000 civilians residing around Bieszczady and Low Beskids were forcibly resettled to former German territories, ceded to Poland at the Yalta Conference at the end of World War II.

The Treaty on the Final Settlement with Respect to Germany (German: Vertrag über die abschließende Regelung in Bezug auf Deutschland),more commonly referred to as the Two Plus Four Agreement (Zwei-plus-Vier-Vertrag),is an international agreement that allowed the reunification of Germany in October 1990. It was negotiated in 1990 between the 'two', the Federal Republic of Germany and the German Democratic Republic, in addition to the Four Powers which had occupied Germany at the end of World War II in Europe: France, the Soviet Union, the United Kingdom, and the United States. The treaty supplanted the 1945 Potsdam Agreement: in it, the Four Powers renounced all rights they had held with regard to Germany, allowing for its reunification as a fully sovereign state the following year. Additionally, the two German states agreed to reconfirm the existing border with Poland in the German–Polish Border Treaty, accepting that German territory post-reunification would consist only of what was presently administered by West and East Germany—renouncing explicitly any possible claims to the former eastern territories of Germany including East Prussia, most of Silesia, and the eastern parts of Brandenburg and Pomerania.

Central Germany (German: Mitteldeutschland [ˈmɪtl̩ˌdɔʏtʃlant] ) is an economic and cultural region in Germany. Its exact borders depend on context, but it is often defined as being a region within the federal states of Saxony, Thuringia and Saxony-Anhalt, or a smaller part of this region, such as the metropolitan area of Leipzig and Halle plus the surrounding counties.

The name dates from the German Empire, when the region was approximately in the centre of the country. Since the German Empire's eastern territories became part of Poland and Russia in the aftermath of World War II, "Central Germany" has been located east of the centre of the country, but the name is still often used in business, media and by the Central German Metropolitan Region. Against this background, the term is not or no longer to be understood as a geographic term.

Central German or Middle German (German: mitteldeutsche Dialekte, mitteldeutsche Mundarten, Mitteldeutsch) is a group of High German languages spoken from the Rhineland in the west to the former eastern territories of Germany.

Central German divides into two subgroups, West Central German and East Central German.

Seventeen days after the German invasion of Poland in 1939, which marked the beginning of the Second World War, the Soviet Union entered the eastern regions of Poland (known as the Kresy) and annexed territories totalling 201,015 square kilometres (77,612 sq mi) with a population of 13,299,000. Inhabitants besides ethnic Poles included Belarusian and Ukrainian major population groups, and also Czechs, Lithuanians, Jews, and other minority groups.

These annexed territories were subsequently incorporated into the Lithuanian, Byelorussian, and Ukrainian Soviet Socialist Republics and remained within the Soviet Union in 1945 as a consequence of European-wide territorial rearrangements configured during the Tehran Conference of 1943 (see Western Betrayal). Poland was compensated for this territorial loss with the pre-War German eastern territories, at the expense of losing its eastern regions. The Polish People's Republic regime described the territories as the "Recovered Territories". The number of Poles in the Kresy in the year 1939 was around 5.274 million, but after ethnic cleansing in 1939-1945 by Nazi Germany, the Soviet Union and Ukrainian nationalist forces, Kresy consisted of approximately 1.8 million inhabitants. The post-World War II territory of Poland was slightly smaller than the pre-1939 land areas, shrinking by some 77,000 square kilometres (30,000 sq mi) (roughly equalling that of the territories of Belgium and the Netherlands combined).

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.