The numerical and technical inferiority, as well as the intervention of the Red Army on September 17, caused the swift surrender of the Polish armed forces. A border and friendship treaty established the German-Soviet demarcation line along the Bug on September 28th. Among the around 13 million residents in those annexed by the USSR and on 1/2. 11. In 1939 the Eastern Polish territories incorporated into the Byelorussian and Ukrainian Soviet Republics were 5.275 million people with Polish as their mother tongue who were immediately subjected to denationalization measures. The deportations carried out in five waves from April 1940 to June 1941 recorded v. a. the state, religious and cultural representatives of Poland; of the roughly 300,000 prisoners of war, only 82,000 survived.
The western voivodeships of Poland with the most important industrial centers, around 90,000 km2 with 10 million residents, were directly attached to the German Reich on October 8, 1939, and the 98,000 km2 area with 10.6 million predominantly Polish residents was included in a general government under Reich Minister H. Frank. This “outlying country of the empire” was ruthlessly exploited and its population oppressed while persecuting its intellectual class. In the “integrated eastern regions” too, the German occupying power suppressed every national movement through expropriation, deportation and targeted extermination and pursued a brutal policy of Germanization. Almost 3 million Polish Jews were murdered in the German concentration camps.
Under Władysław Raczkiewicz (* 1885, † 1947; as President) and W. Sikorski (as Prime Minister), a government in exile was formed in 1939/40 – first in Paris, then in London. After the German attack on the USSR presented General W. Anders based on a Soviet-Polish agreement (30. 7. 1941) of Polish prisoners of war in the USSR an exile army, which the government in exile but in 1942 increased in the wake tensions with Stalin in moved to Iran.
The persistent Polish demand for an explanation for the Katyn corpses discovered on April 13, 1943 prompted Stalin on April 25 to break off diplomatic relations with the government in exile and to unilaterally support the communist-left socialist forces.
In addition, the government-in-exile under Prime Minister Stanisław Mikołajczyk (* 1901, † 1966; 1943–44) and Tomasz Arciszewski (* 1877, † 1955; 1944–47) refused to agree to the loss of the areas east of the Bug and a westward shift in Poland.
The brutal German occupation policy triggered a willingness to resist in the underground struggle, which was spreading across the population. On the one hand, the Armia Krajowa (AK), which operated in conjunction with the government-in-exile and had around 300,000 men at its disposal at the end of 1943, was formed; on the other hand, the Communist People’s Guard (Gwardia Ludowa), based on the Polish Workers’ Party (PPR, re-established in 1942), was formed. whose military importance remained relatively insignificant even after its transformation into Armia Ludowa (AL) in early 1944. In April / May 1943, the German occupying power brutally suppressed the uprising in the Warsaw ghetto, which was supposed to stop the transport of the last 60,000 Jews remaining there to the extermination camps (Warsaw Uprising 1). When the Red Army crossed the Bug in July 1944 and the Lublin Committee (Polish Committee for National Liberation), formed by forces loyal to Moscow, set up a communist-oriented administration, the AK triggered an uprising on August 1, 1944, which the German armed forces, however, up to suppressed on October 2, 1944 (Warsaw Uprising 2). As part of the Soviet winter offensive launched on January 12, 1945, the German armed forces were pushed back. According to ethnicityology, after the liberation of Poland, the Lublin Committee, renamed the Provisional Government on January 1, 1945, took over rule in Poland, and at the same time as the advance of the Red Army took over administration in southern East Prussia, Danzig, Pomerania, Silesia and eastern Brandenburg. The cession of eastern Poland and compensation by German eastern territories, which had already been discussed at the Tehran Conference (November / December 1943), sparked tensions between the government in exile and the Western Allies; Nevertheless, at the Yalta Conference (February 1945) the slightly modified Curzon Line was established as the Polish eastern border and Poland was given the prospect of “a considerable increase in territory in the west and north”. The refusal of the Provisional Government to accept politicians in exile and representatives of the bourgeois-democratic camp in adequate numbers delayed the formation of a “government of national unity” until June 28, 1945. Thereupon the Potsdam Conference (17. 7. – 2. 8. 1945) placed the former East German areas up to the Oder and Lusatian Neisse as well as southern East Prussia and Danzig (103,000 km2) under Polish administration. In return, Poland had around 180,000 km east of the Curzon Line2 with 12 million residents in favor of the USSR. With the expulsion of most of the Germans and the forced resettlement of the Poles from the Polish eastern areas, a huge population shift took place. Poland only covered 312 730 km 2 with just under 24 million residents.