It has been suggested that this article be merged into Territorial changes of Poland immediately after World War II. (Discuss) Proposed since November 2021.
The Recovered Territories or Regained Lands (Polish: Ziemie Odzyskane), also known as Western Borderlands (Polish: Kresy Zachodnie), and previously as Western and Northern Territories (Polish: Ziemie Zachodnie i Północne), Postulated Territories (Polish: Ziemie Postulowane) and Returning Territories (Polish: Ziemie Powracające), are the former eastern territories of Germany and the Free City of Danzig that became part of Poland after World War II, at which time their former German inhabitants were forcibly deported. The rationale for the term "Recovered" was that these territories formed part of the Polish state, and were lost by Poland in different periods over the centuries. It also referred to the Piast Concept that these territories were part of the traditional Polish homeland under the Piast dynasty, after the establishment of the state in the Middle Ages. Over the centuries, however, they had become predominantly German-speaking through the processes of German eastward settlement (Ostsiedlung), political expansion (Drang nach Osten), as well as language shift due to assimilation (see also: Germanisation) of local Polish, Slavic and Baltic Prussian population. Therefore, aside from certain regions such as West Upper Silesia, Warmia and Masuria, as of 1945 most of these territories did not contain sizeable Polish-speaking communities.
While most regions had long periods of Polish rule, spanning hundreds of years, some were controlled by Polish dukes and kings for short periods of up to several decades at a time. Various regions, after losing power over them by Poland, were in different times under the authority of the Bohemian (Czech) Kingdom, Hungary, Austria, Sweden, Denmark, Brandenburg, Prussia, and all of these territories to 1920/1945 were part of Germany. Many areas were also part of various Polish-ruled duchies, created as a result of the fragmentation of Poland, which began in the 12th century. The fact that some regions were located within the borders of Poland for a short time is used by opponents of the term to suggest that the argument of traditional Polish homeland is based rather on nationalistic ideas than on historical facts, although all these areas were at some point under Polish rule, and many regions have a rich Polish history.
The great majority of the previous inhabitants either fled from the territories during the later stages of the war or were expelled by the Soviet and Polish communist authorities after the war ended, although a small German minority remains in some places. The territories were resettled with Poles who moved from central Poland, Polish repatriates forced to leave areas of former eastern Poland that had been annexed by the Soviet Union, Poles freed from forced labour in Nazi Germany, with Ukrainians, Rusyns forcibly resettled under "Operation Vistula", and other minorities, which settled in post-war Poland, including Greeks and Macedonians.
However, contrary to the official declaration that the former German inhabitants of the Recovered Territories had to be removed quickly to house Poles displaced by the Soviet annexation, the Recovered Territories initially faced a severe population shortage. The Soviet-appointed communist authorities that conducted the resettlement also made efforts to remove many traces of German culture, such as place names and historic inscriptions on buildings, from the newly Polish territories.
The post-war border between Germany and Poland (the Oder–Neisse line) was recognized by East Germany in 1950 and by West Germany in 1970, and was affirmed by the re-united Germany in the German–Polish Border Treaty of 1990.