Beria was the longest-lived and most influential of Stalin 's secret police chiefs , wielding his most substantial influence during and after World War II . Following the Soviet invasion of Poland in 1939 he was responsible for organizing the Katyn massacre . He simultaneously administered vast sections of the Soviet state and acted as the '' de facto '' Marshal of the Soviet Union in command of NKVD field units responsible for barrier troops and Soviet partisan intelligence and sabotage operations on the Eastern Front during World War II . Beria administered the vast expansion of the Gulag labor camps and was primarily responsible for overseeing the secret detention facilities for scientists and engineers known as '' sharashkas ''
Katyn massacre
Katyn massacre
Lavrentiy Beria