The complete subjugation of the party to Stalin, its leader, paralleled the subordination of industry and agriculture to the state. Stalin had assured his preeminent position by squelching Bukharin and the "right-wing deviationists" in 1929 and 1930. To secure his absolute control over the party, however, Stalin began to purge leaders and rank-and-file members whose loyalty he doubted.
Stalin's purges began in December 1934, when Sergey Kirov, a popular Leningrad party chief who advocated a moderate policy toward the peasants, was assassinated. Although details remain murky, many Western historians believe that Stalin instigated the murder to rid himself of a potential opponent. In any event, in the resultant mass purge of the local Leningrad party, thousands were deported to camps in Siberia. Zinov'yev and Kamenev, Stalin's former political partners, received prison sentences for their alleged role in Kirov's murder. At the same time, the People's Commissariat for Internal Affairs (Narodnyy komissariat vnutrennikh del--NKVD), the secret police agency that was heir to the Cheka of the early 1920s, stepped up surveillance through its agents and informers and claimed to uncover anti-Soviet conspiracies among prominent long-term party members. At three publicized show trials held in Moscow between 1936 and 1938, dozens of these Old Bolsheviks, including Zinov'yev, Kamenev, and Bukharin, confessed to improbable crimes against the Soviet state. Their confessions were quickly followed by execution. (The last of Stalin's old enemies, Trotsky, who supposedly had masterminded the conspiracies against Stalin from abroad, was murdered in Mexico in 1940, presumably by the NKVD.) Coincident with the show trials of the original leadership of the party, unpublicized purges swept through the ranks of younger leaders in party, government, industrial management, and cultural affairs. Party purges in the non-Russian republics were particularly severe. The Yezhovshchina ("era of Yezhov," named for NKVD chief Nikolay Yezhov) ravaged the military as well, leading to the execution or incarceration of about half the officer corps. The secret police also terrorized the general populace, with untold numbers of common people punished after spurious accusations. By the time the purges subsided in 1938, millions of Soviet leaders, officials, and other citizens had been executed, imprisoned, or exiled.
The reasons for the period of widespread purges, which became known as the Great Terror, remain unclear. Western historians variously hypothesize that Stalin created the terror out of a desire to goad the population to carry out his intensive modernization program, or to atomize society to preclude dissent, or simply out of brutal paranoia. Whatever the causes, the purges must be viewed as having weakened the Soviet state.
In 1936, just as the Great Terror was intensifying, Stalin approved a new Soviet constitution to replace that of 1924. Hailed as "the most democratic constitution in the world," the 1936 document stipulated free and secret elections based on universal suffrage and guaranteed the citizenry a range of civil and economic rights. But in practice the freedoms implied by these rights were denied by provisions elsewhere in the constitution that indicated that the basic structure of Soviet society could not be changed and that the party retained all political power.
The power of the party, in turn, now was concentrated in the persons of Stalin and the members of his handpicked Politburo. As if to symbolize the lack of influence of the party rank and file, party congresses were convened less and less frequently. State power, far from "withering away" after the revolution as Karl Marx had prescribed, instead grew. With Stalin consciously building what critics would later describe as a cult of personality, the reverence accorded him in Soviet society gradually eclipsed that given to Lenin.