Polish prisoners-of-war in the Soviet Union after 1939

As a result of the Soviet invasion of Poland in 1939, hundreds of thousands of Polish soldiers became prisoners of war in the Soviet Union. Many of them were executed; over 20,000 Polish military personnel and civilians perished in the Katyn massacre.

On September 17, 1939, the Red Army invaded the territory of Poland from the east. The invasion took place while Poland was already sustaining serious defeats in the wake of the German attack on the country that started on September 1, 1939. The Soviets moved to safeguard their claims in accordance with the Molotov-Ribbentrop Pact.

During the Red Army's rapid advance, about 6,000–7,000 Polish soldiers died in the fighting, 230,000–450,000 were taken prisoner—230,000 immediately after the campaign and 70,000 more when the Soviets annexed the Baltic States and assumed custody of Polish troops interned there.

The Soviets often failed to honour the terms of surrender. In some cases, they promised Polish soldiers freedom after capitulation and then arrested them when they laid down their arms. Some Polish soldiers were murdered shortly after capture, like General Józef Olszyna-Wilczyński, who was taken prisoner, interrogated and shot on September 22, during the invasion itself. On September 24, the Soviets murdered forty-two staff and patients at a Polish military hospital in the village of Grabowiec near Zamość. After a tactical Polish victory at the battle of Szack on September 28, where the combined Korpus Ochrony Pogranicza (KOP) or Border Protection Corps forces, under General Wilhelm Orlik-Rueckemann, routed the Soviet 52nd Rifle Division, the Soviets executed all the Polish officers they captured. The Soviets also executed hundreds of defenders at Grodno, the exact number of those killed has not been established.

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