Neumark in the context of "Duchy of Pomerania"

The entirety of Germany was occupied and administered by the Allies of World War II, from the Berlin Declaration on 5 June 1945 to the establishment of West Germany on 23 May 1949. Unlike occupied Japan, Nazi Germany was stripped of its sovereignty and its government was entirely dissolved. After Germany formally surrendered on Tuesday, 8 May 1945, the four countries representing the Allies (the United States, United Kingdom, Soviet Union, and France) asserted joint authority and sovereignty through the Allied Control Council (ACC).

Germany after the war was a devastated country – roughly 80 percent of its infrastructure was in need of repair or reconstruction – which helped the idea that Germany was entering a new phase of history ("zero hour"). At first, Allied-occupied Germany was defined as all territories of Germany before the 1938 Nazi annexation of Austria. The Potsdam Agreement on 2 August 1945 defined the new eastern German border by giving Poland and the Soviet Union all regions of Germany east of the Oder–Neisse line (eastern parts of Pomerania, Neumark, Posen-West Prussia, East-Prussia and most of Silesia) and divided the remaining "Germany as a whole" into four occupation zones, each administered by one of the Allies.

The State of the Teutonic Order (German: Staat des Deutschen Ordens, pronounced [ˈʃtaːt dɛs ˌdɔʏtʃn̩ ˈʔɔʁdn̩s] ) was a theocratic state located along the southeastern shore of the Baltic Sea in northern Europe. It was formed by the knights of the Teutonic Order during the early 13th century Northern Crusades in the region of Prussia. In 1237, the Livonian Brothers of the Sword merged with the Teutonic Order of Prussia and became known as its branch – the Livonian Order (while their state, Terra Mariana, covering present-day Estonia, Latvia, and a small part of Russia, became part of the State of the Teutonic Order). At its greatest territorial extent during the early 15th century, the State encompassed Chełmno Land, Courland, Gotland, Livonia, Estonia, Neumark, Pomerelia (Gdańsk Pomerania), Prussia and Samogitia.

Following the battles of Grunwald in 1410 and Wilkomierz in 1435, the State fell into decline. After losing extensive territories in the imposed Peace of Thorn in 1466, the extant territory of its Prussian branch became known as Monastic Prussia (Polish: Prusy zakonne) or Teutonic Prussia (Polish: Prusy krzyżackie). It existed until 1525 as a fiefdom of the Polish Crown. The Livonian branch joined the Livonian Confederation and continued to exist as part of it until 1561.

During the later stages of World War II and the post-war period, Reichsdeutsche (German citizens) and Volksdeutsche (ethnic Germans living outside the Nazi state) fled and were expelled from various Eastern and Central European countries, including Czechoslovakia, and from the former German provinces of Lower and Upper Silesia, East Prussia, and the eastern parts of Brandenburg (Neumark) and Pomerania (Farther Pomerania), which were annexed by the Provisional Government of National Unity of Poland and by the Soviet Union.

The idea to expel the Germans from the annexed territories had been proposed by Winston Churchill, in conjunction with the Polish and Czechoslovak governments-in-exile in London since at least 1942. Tomasz Arciszewski, the Polish prime minister in-exile, supported the annexation of German territory but opposed the idea of expulsion, wanting instead to naturalize the Germans as Polish citizens and to assimilate them. Joseph Stalin, in concert with other Communist leaders, planned to expel all ethnic Germans from east of the Oder and from lands which from May 1945 fell inside the Soviet occupation zones. In 1941, his government had already transported Germans from Crimea to Central Asia.

The former eastern territories of Germany (German: ehemalige deutsche Ostgebiete) refer to those territories east of the current eastern border of Germany, i.e. the Oder–Neisse line, which historically had been considered German and which were annexed by Poland and the Soviet Union after World War II. In contrast to the lands awarded to the restored Polish state by the Treaty of Versailles after World War I, the German territories lost with the post-World War II Potsdam Agreement were either almost exclusively inhabited by Germans before 1945 (the bulk of East Prussia, Lower Silesia, Farther Pomerania, and parts of Western Pomerania, Lusatia, and Neumark), mixed German–Polish with a German majority (the Posen–West Prussia Border March, Lauenburg and Bütow Land, the southern and western rim of East Prussia, Ermland, Western Upper Silesia, and the part of Lower Silesia east of the Oder), or mixed German–Czech with a German majority (Glatz). Virtually the entire German population of the territories that did not flee voluntarily in the face of the Red Army advance of 1945, was violently expelled to Germany, with their possessions being forcibly expropriated.

The ceding of the east German lands to Poland was done in large part to compensate Poland for losing the Kresy lands east of the Curzon line, a region that was annexed by the Soviet Union after the German invasion of Poland in 1939. This territory had large populations of Ukrainians, Belarusians and Lithuanians – the main ethnic groups of three of the western republics of the Soviet Union – and many towns that were primarily inhabited by Poles and Jews. The Jewish communities in this region were mostly exterminated in the Holocaust and the Polish communities were mostly expelled to the restored Polish state after World War II, the communist-ruled Polish People's Republic. Poles from the northern part of Kresy were primarily resettled in Pomerania and Poles from Galicia were primarily resettled in Silesia, e.g. the Ossolineum and the Jan Kazimierz University in Lwów were both relocated to Wrocław, the former Breslau.