The "Polish operation" by the Soviet NKVD was a criminal operation conducted in the Soviet Union between 1937 and 1938, which resulted in the sentencing of at least 139,835 people - mostly Poles. The vast majority of them - no less than 111,091 people - were shot in the back of the head. The crime was committed under the fictitious charge of conducting espionage and subversive activities for Poland. The Institute of National Remembrance has undertaken numerous activities to reveal this unprecedented, but well-known only to specialists, crime, and to bring it to its full explanation. For this purpose the IPN initiated an investigation into the case of the Polish operation (qualifying it as a communist crime being a crime against humanity). In addition, it organized, in cooperation with the Office of the President of the Republic of Poland and the Center for Polish-Russian Dialogue and Understanding, an international scientific conference "Polish Operation by the NKVD 1937- 1938. Restoring remembrance of the crime”. Among such initiatives one should also mention the issuing by the Polish Post of a stamp dedicated to the crime committed on Poles.