Towards the Great Terror
On 1 December 1934 Kirov was murdered in his offices in the Smolny Institute by a disgruntled Party member known to be a danger but unstopped by the NKVD. Stalin's complicity in the assassination cannot be proved. But there is no doubt that he used it to eliminate his political enemies.
Within hours of the murder, Stalin took control of the investigation and passed an emergency decree (approved by the Politburo only two days later) ordering summary trials and executions of suspected 'terrorists' (6,500 people were arrested under the new law in December alone).
Stalin announced that the 'Zinovievites' were responsible for the murder of Kirov (Zinoviev was a former Party boss of Leningrad) and demanded their arrest as 'German Fascist White-Guard spies' (843 former associates of Zinoviev were arrested in January-February 1935). The campaign of repression quickly spread through Leningrad: 11,000 'former people' were arrested and sent to camps or places of exile.
A purge of the Party expelled 250,000 members - most of them suspected as oppositionists by the NKVD - during 1935. The NKVD's close involvement in a Party purge was something new. It set the pattern for the Great Terror.