[6] The post of general secretary lacked clear guidelines of succession, so after the death or removal of a Soviet leader the successor needed the support of the Political Bureau (Politburo), the Central Committee, or another government or party apparatus to both take and stay in power.
[9] After the failed coup in August 1991, the vice president was replaced by an elected member of the State Council of the Soviet Union.
Stalin continued to increase his influence in the party, and by the end of the 1920s, he became the sole dictator of the USSR, defeating all his political opponents.
[15] As leader of the Politburo, Stalin consolidated near-absolute power by 1938 after the Great Purge, a series of campaigns of political murder, repression and persecution.
[18] Stalin died in March 1953[19] and his death triggered a power struggle in which Nikita Khrushchev after several years emerged victorious against Georgy Malenkov.
[21] As Khrushchev grew older, his erratic behaviour became worse, usually making decisions without discussing or confirming them with the Politburo.
[27] Following Andropov's death fifteen months after his appointment, an even older leader, 72-year-old Konstantin Chernenko, was elected to the general secretariat.
[29] In May 1985, Gorbachev publicly admitted the slowing down of the economic development and inadequate living standards, being the first Soviet leader to do so while also beginning a series of fundamental reforms.
He also opened up the management of and decision-making within the Soviet Union and allowed greater public discussion and criticism, along with the warming of relationships with the West.
On four occasions the Soviet Union was governed by a council known as a troika (i.e."triumvirate"),[59] whereby policymaking depended on the consensus of three chief figures within the Politburo.