 He was one of the main collaborators of Nikolai Yezhov, head of the NKVD in the years 1936–1938, and collaborator of other organizers of the Great Terror in the USSR.On August 16, 1937, he became the head of the board of the communist concentration camps GULAG NKVD five days after the beginning of Polish Operation of the NKVD.According to NKVD documents, 139,835 Poles who were citizens of the USSR were convicted in 1937.