After the start of the German invasion of the Soviet Union on June 22, 1941, NKVD troops were supposed to evacuate political prisoners to the interior of the Soviet Union, but the hasty retreat of the Red Army, a lack of transportation and other supplies, and general disregard for legal procedures often led to prisoners being simply executed.

Estimates of the death toll vary by location; nearly 9,000 in the Ukrainian SSR,[1] 20,000–30,000 in eastern Poland (now part of Western Ukraine),[2] with the total number reaching approximately 100,000 extrajudicial executions in the span of a few weeks.

[4] "It was not only the numbers of the executed", wrote historian Yury Boshyk, who was quoted by Orest Subtelny, of the murders, "but also the manner in which they died that shocked the populace.

When the families of the arrested rushed to the prisons after the Soviet evacuation, they were aghast to find bodies so badly mutilated that many could not be identified.

[8] By 1941, much of the ethnically Polish population living under Soviet rule in the eastern half of Poland had already been deported to remote areas of the USSR.

[22] In Soviet-occupied western Ukraine, under the threat of German invasion NKVD committed various mass murders of prison inmates, including: "From the courtyard, doors led to a large space, filled from top to bottom with corpses...Among them were many women.