In the early 1930s, there were growing concerns about the effect of Stalins economic policies as many believed that collectivisation had been introduced too quickly and too brutally and that industrialisation had been done without enough concern for its effects on the lives of the people. Several members within the communist party were beginning to question Stalins leadership and some were even considering the possibility of replacing Stalin as the General Secretary. On top of this Stalin was facing an increasing external threat in the form of Nazi Germany with the knowledge that Hitler hated communism and he often spoke of the inevitability of a war with the USSR.
Ryutin challenged Stalins authority and undermined him during the Ryutin affair in 1932. Ryutin called for a fresh start and wrote that Stalin was a grave-digger of the revolution. Following this, Stalin demanded his immediate arrest and execution, however his party colleagues argued against the execution and eventually saved him. Ryutin was sentenced to 10 years imprisonment, though he was eventually executed in 1937. Importantly though, the affair had highlighted how Stalin still didn't have complete control over the party, which may in part explain why his early purges focused in on the party itself.
Sergei Kirov was the Chairman of the Leningrad soviet and a leading figure in the Communist Party. In 1934, he threatened Stalins dominance. He was handsome, charismatic and popular within the party and unlike Stalin, he was actually Russian which further enhanced his appeal. As a hard line communist he was linked to moderates in the party who were unhappy with the shortcomings of the first five-year plan and had argued for a better standard of living for the industrial workers. On top of this, he had been one of the members of the party to have argued against the execution of Ryutin. After Stalins death in 1953, it had emerged that at the 1934 Party Congress of Victors, Stalin had received over a hundred votes against his re-election into the Central Committee as well as Kirov receiving 300 more votes that Stalin to top the poll, thus emphasising the extent of the resistance that had grown up against Stalin, contrasted to the ever increasing popularity of Kirov. However, on the first of December 1934, Kirov was murdered in his office in Leningrad by Leonid Nikolayev. It's still unclear whether or not Stalin actually ordered Kirov's murder, but he did use the incident as a stepping stone for the unleashing of his purges against his opposition.
Stalin claimed that the assassination of Kirov was not the act of a lone gunman, but was part of a widespread conspiracy against the government, and as a result Stalin used this to arrest and executed his enemies within the party. The murderer, Nikolayev, was personally interrogated by Stalin and confessed that Trotsky, Zinoviev and over 100 political figures had asked him to carry out the murder. The Leningrad party was one of the first targets of Stalins purges as…