Analysis of information sources in references of the Wikipedia article "Police state" in English language version.
[Ivan IV] established a political security force to run the Oprichina[sic], whose task was to spy on his enemies and destroy them; hence Ivan may be regarded as the inventor of the police state.
Oprichnina was originally a band of faithful servants organized by Ivan IV into a police force; they were used by the tsar to crush not only all boyars (Russian nobility) under suspicion, but also the Russian princes [...]. Oprichnina enabled the tsars to build the first police state in modem history.