In April 1940, on orders signed by Joseph Stalin, the Soviet NKVD launched a secret execution operation that killed more than 22,000 Polish citizens.

Among them were approximately 8,000 Polish Army officers, around 6,000 police officers and members of other uniformed services, and nearly 8,000 civilians, including professors, priests, judges, and state officials — the intellectual and military elite of Poland.

Captured after the Soviet invasion of eastern Poland in September 1939, the prisoners were taken from camps such as Kozelsk, Starobelsk, and Ostashkov and executed in NKVD prisons and forest sites near Katyń, Kalinin, and Kharkiv. Shot one by one in the back of the head, they were buried in mass graves.

For decades, the Soviet Union denied responsibility. The truth was officially admitted only in 1990.

The Katyń massacre remains one of the most systematic and politically explosive crimes of World War II.