The policies of Stalin were aimed at suppressing dissent and marginalizing his political rivals. This was achieved by a variety of means. One was the establishment of a police state. Using the NKVD, a secret police organization that imprisoned people suspected of expressing ideas contrary to those of Stalin. Thousands were executed, imprisoned, sent to forced labor camps, or simply harassed by secret police. These efforts were particularly intense during the Purges of 1936, when the NKVD, under the control of Nikolai Yezhov, oversaw the murder of thousands of Stalin's political rivals (and those suspected of holding non-orthodox opinions.) Even Yezhov himself eventually vanished. So the effect of Stalin's policies on his opponents was generally nightmarish.