timelets

The most persecuted European national minority in the second half of the 1930s was not the four hundred thousand or so German Jews (the number declining because of emigration) but the six hundred thousand or so Soviet Poles (the number declining because of executions).
Stalin was a pioneer of national mass murder, and the Poles were the preeminent victim among the Soviet nationalities.
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In addition to the traditional conveyer method and the standing method, many Soviet Poles were subjected to a form of collective torture called the “conference method.” Once a large number of Polish suspects had been gathered in a single place, such as the basement of a public building in a town or village of Soviet Ukraine or Soviet Belarus, a policeman would torture one of them in full view of the others. Once the victim had confessed, the others would be urged to spare themselves the same sufferings by confessing as well.

Soviet Poles were about forty times more likely to die during the Great Terror than Soviet citizens generally.

In the twenty-one months that followed the joint German-Soviet invasion of Poland, the Germans and the Soviets would kill Polish civilians in comparable numbers for similar reasons, as each ally mastered its half of occupied Poland. --- Snyder, T. Bloodlands. Ch 3. 2012.