Question: What is the name of this series of mass executions during World War II, which, along with Sambor Ghetto, was anenexed to the Ukranian SSR?
Sentence (from "NKVD prisoner massacres"): The NKVD prisoner massacres were a series of mass executions carried out by the Soviet NKVD secret police during World War II against political prisoners across Eastern Europe, primarily Poland, Ukraine, the Baltic states, Bessarabia and other parts of the Soviet Union from which the Red Army was retreating following the Nazi German attack on the Soviet positions in occupied Poland, known as Operation Barbarossa.
Relevant evidence: Yes