Why did stalin carry out the purges?
Stain's position as leader was under threat in 1934. There had been many calls for his removal, and many Communists wanted to build better relations with people. Stalin, for his part, was convinced that he was the only person who could transform the Soviet Union into a modern, industrialised country, and that it had to be done quickly. He was obsessed by the idea that Hitler would attack the USSR and that it would lose the war if it could not produce enough armaments. To interfere in the pace of industrialisation, would be a betrayal of the Soviet Union.
Stalin thought it would be important to remain leader for many reasons.
First of all, he believed that he was the only one that could pull Russia through collectivization in the 1930s, and industrialise it successfully. His self-confidence reflected itself in success, which showed its real significance when the USSR fought in the Second World War in 1941.
Stalin's ruthless is what stands out when people compare him to other potential leaders (e.g. Trotsky, Lenin (if not dead). Many would say that Lenin would be able to pull Russia through this devastating process, and that he was ruthless enough, because it was him that introduced the labour and prison camps in the 1920s. The biggest argument to show that Lenin was not capable of achieving what Stalin has, is Lenin's own testimony, written before he died in 1924. In this testimony Lenin comments on Stalin's ruthlessness, and states that Stalin should be removed from his job as general secretary. This shows us that by commenting on the excess of Stalin's ruthlessness, Lenin suggests that it is too much, and that Stalin's ruthlessness and brutality are on a much higher level than Lenin's.