Katyn Massacre
In 1940, the Soviet NKVD took over 20,000 Polish military officials intellectuals prisoner. One-by-one, the prisoners had been taken to mass graves in Katyn woodland and chance into the head. These were killed, buried, then the criminal activity against humanity ended up being blamed in the invading German Nazis. The planet thought this to be real until 1990 when Russia eventually admitted it was accountable.
