The history of Poland from 1939 to 1945 encompasses primarily the period from the invasion of Poland by Nazi Germany and the Soviet Union to the end of World War II.
Following the German–Soviet non-aggression pact, Poland was invaded by Nazi Germany on 1 September 1939 and by the Soviet Union on 17 September. The campaigns ended in early October with Germany and the Soviet Union dividing and annexing the whole of Poland. After the Axis attack on the Soviet Union in the summer of 1941,
the entirety of Poland was occupied by Germany, which proceeded to advance its racial and genocidal policies across Poland.
Under the two occupations, Polish citizens suffered enormous human and material losses.
According to the Institute of National Remembrance estimates, about 5.6 million Polish citizens died as a result of the German occupation and about 150,000 died as a result of the Soviet occupation.
The Jews were singled out by the Germans for a quick and total annihilation and about 90 percent of Polish Jews (close to three million people) were murdered as part of the Holocaust.
Jews, Poles, Romani people and prisoners of many other ethnicities were killed masse at Nazi extermination camps, such as Auschwitz, Treblinka and Sobibór.
Ethnic Poles were subjected to both Nazi German and Soviet persecution. The Germans killed an estimated two million ethnic Poles.
They had future plans to turn the remaining majority of Poles into slave labor and annihilate those perceived as “undesirable” as part of the wider Generalplan Ost.
Ethnic cleansing and massacres of Poles and to a lesser extent Ukrainians were perpetrated in western Ukraine (prewar Polish Kresy) from 1943. The Poles were murdered by Ukrainian nationalists.
In September 1939, the Polish government officials sought refuge in Romania, but their subsequent internment there prevented the intended continuation abroad as the government of Poland.
General Władysław Sikorski, a former prime minister, arrived in France, where a replacement Polish Government-in-Exile was soon formed.
After the fall of France, the government was evacuated to Britain. The Polish armed forces had been reconstituted and fought alongside the Western Allies in France, Britain and elsewhere.
Resistance movement began organizing in Poland in 1939, soon after the invasions.
Its largest military component was a part of the Polish Underground State network of organizations and activities and became known as the Home Army.
The whole clandestine structure was formally directed by the Government-in-Exile through its delegation resident in Poland.
There were also peasant, right-wing, leftist, Jewish and Soviet partisan organizations.
Among the failed anti-German uprisings were the Warsaw Ghetto Uprising and the Warsaw Uprising.
The aim of the Warsaw Uprising was to prevent domination of Poland by the Soviet Union.
In order to cooperate with the Soviet Union, after Operation Barbarossa an important war ally of the West, Sikorski negotiated
in Moscow with Joseph Stalin and they agreed to form a Polish army in the Soviet Union, intended to fight on the Eastern Front alongside the Soviets.
The “Anders’ Army” was instead taken to the Middle East and then to Italy.
Further efforts to continue the Polish-Soviet cooperation had failed because of disagreements over the borders, the discovery of the Katyn massacre of Polish POWs perpetrated by the Soviets, and the death of General Sikorski.
Afterwards, in a process seen by many Poles as a Western betrayal, the Polish Government-in-Exile gradually ceased being a recognized partner in the Allied coalition.
Stalin pursued a strategy of facilitating the formation of a Polish government independent of (and in opposition to) the exile government in London by empowering the Polish communists.
Among Polish communist organizations established during the war were the Polish Workers’ Party in occupied Poland and the Union of Polish Patriots in Moscow.
A new Polish army was formed in the Soviet Union to fight together with the Soviets.
At the same time Stalin worked on co-opting the Western Allies (the United States led by President Franklin D. Roosevelt and the United Kingdom led by Prime Minister Winston Churchill), who, in terms of practical implementations, conformed to Stalin’s views on Poland’s borders and future government.
The fate of Poland had been determined in a series of negotiations that included the conferences in Tehran, Yalta, and Potsdam.
In 1944, the Polish Government-in-Exile approved and the underground in Poland undertook unilateral political and military actions aimed at establishing an independent Polish authority, but the efforts were thwarted by the Soviets.
The Polish communists founded the State National Council in 1943/44 in occupied Warsaw and the Polish Committee of National Liberation in July 1944 in Lublin, after the arrival of the Soviet army. The Soviet Union kept the eastern half of prewar Poland,
granting Poland instead the greater southern portion of the eliminated German East Prussia and shifting the country west to the Oder–Neisse line, at the expense of Germany.
