Mass operations of the NKVD
Mass operations of the People's Comissariate of Internal Affairs (NKVD) were carried out during the Great Purge and targeted specific categories of people. As a rule, they were carried out according to the corresponding order of the People's Commissar of Internal Affairs Nikolai Yezhov.
Source: Wikipedia — Mass operations of the NKVD (CC BY-SA 4.0)