Look at what Aleksandr Solzhenitsyn wrote about how Soviets used terror to control their prisoners on the Solovetsky Islands:
And in 1926 the inveterate habitual-criminal elements of all sorts began to flood in. And how were they all to be kept in check, kept from rebelling?
Only by terror! Only with Sekirnaya Hill! With poles! With mosquitoes! By being dragged through stumps! By daytime executions!
The Gulag Archipelago, Volume 2, p 43