Monument in Kalisz

The Katyn massacre was a series of mass executions of nearly 22,000 Polish military officers and intelligentsia carried out by the Soviet Union, specifically the NKVD - the Soviet secret police in April and May 1940. Though the killings also occurred in the Kalinin and Kharkiv prisons and elsewhere, the massacre is named after the Katyn Forest, where some of the mass graves were first discovered. source: Wikipedia

The Polish soldiers and inteligentia's places of executions

The Polish soldiers' photos murdered in Katyn, Ostaszkow, Starobielsk by NKVD.