Polish students learn about the Katyn massacre on Grodzka street, on 23rd September 2019, in Krakow, Malopolska, Poland. The Katyn massacre was a series of mass executions of Polish military officers and intelligentsia carried out by Soviet secret police in April and May 1940. Though the killings occurred in several locations, the massacre is named after the Katyn Forest, where some of the mass graves were first discovered.