The Political Bureau of the Central Committee of the Communist Party of the Soviet Union,[a] abbreviated Politbureau CC CPSS[b] or simply Politbureau,[c] was the highest political body of the Central Committee of the Communist Party of the Soviet Union and de facto a collective presidency of the USSR.

However, due to practical reasons, usually fewer than half of the members attended the regular Central Committee meetings during this time, even though they decided all key questions.

The 8th Party Congress in 1919 formalized this reality and re-established what would later on become the true center of political power in the Soviet Union.

[6] In these, Lenin wrote of his plan to turn the combined meetings of the Central Committee and the Control Commission into the party's "parliament".

[6] Admitting that organizational barriers may be inadequate to safeguard the party from one-man dictatorship, Lenin recognized the importance of individuals.

[5] Lenin, a noted factionalist before the Bolshevik seizure of power, supported the promotion of people he had previously clashed with on important issues to the Politburo; Trotsky and Lenin had had several years of violent polemics between them, while Grigori Zinoviev and Lev Kamenev both opposed the Central Committee resolution that initiated the October Revolution.

[9] The nature of democratic centralism had changed by 1929, and freedom of expression, which had been previously tolerated within the party, was replaced with monolithic unity.

[4] Stalin defeated the Left Opposition led by Trotsky by allying himself with the rightists within the Politburo; Nikolai Bukharin, Aleksey Rykov, and Mikhail Tomsky.

[11] Throughout the late-1920s, Politburo member Lazar Kaganovich (a Stalin ally), wrote and campaigned for a party organisational by-law which reduced intra-party democracy in favour of hierarchy and centralism.

"[11] The Secretariat and Orgburo were responsible for personnel appointments in the whole party, and so were used as a machine by Stalin and his allies to promote like-minded individuals.

[15] On 1 December 1934, Kirov was shot dead – whether he was the victim of a lone assailant or killed on Stalin's orders remains unknown.

[15] Not long after, on 21 January 1935, Valerian Kuybyshev died of natural causes, and a month later, Anastas Mikoyan and Vlas Chubar were elected Politburo full members.

[16] At the Central Committee plenum in February 1937, Stalin, Molotov, Zhdanov and Nikolai Yezhov began accusing leading officials of anti-socialist behavior, but they met opposition.

[16] Molotov and Kliment Voroshilov, supported a compromise brokered by Stalin, which handed over Bukharin and Rykov to the NKVD.

[17] In 1938, four other Politburo members were purged; Chubar, who personally telephoned Stalin crying trying to assure his innocence, Kosior, who confessed for anti-socialist crimes after his daughter was raped in front of him, Postyshev and Eikhe.

[17] The purging of Rudzutaks, Eikhe, and Kosior testified to Stalin's growing power; the Politburo were not even notified of the decision.

[19] The General Secretary, the party leader, served as ex officio chairman of the Politburo (however, no formal rule stipulated such activity).

[18] While nominally subordinate to the Central Committee and the Party Congress, in practice the Politburo was the true center of power in the CPSU, and its decisions de facto had the force of law.

"[20] Shevchenko's memoir makes it clear that the tense political struggle that could often occur among Politburo members usually did not take place openly during its meetings, but rather behind the backs of one's rivals.

Shevchenko said,[20] "While the Politburo considered the item for which I was responsible, I sat with Kuznetsov, Kornienko, and [Vasily] Makarov, behind Gromyko at the long table in the Kremlin.

'"[20] Nevertheless, there were times where the General Secretary would override all the other members by making his opinion clear and implying that dissent would not be tolerated.

When he returned from vacation, before the first meeting of the Politburo he said: "Some idiot here invented a plan to close GUM and open some kind of cabinet of curiosities there."

[22] Instead of stepping down, Khrushchev made a rule which stated that members "who enjoyed great authority and possessed exceptional ability" could serve more than three terms, if they received more than 75 percent approval votes from the Central Committee, upon elections.

[24] Article 25 of the Charter remained unchanged under the successive leadership of Yuri Andropov, Konstantin Chernenko and Mikhail Gorbachev.

[30] From 1953 until 1973, no officials representing the security sector served in the Politburo as full members; the last two being Lavrentiy Beria and Nikolay Ignatov.

[30] This tradition was put to an end with the elevation of Yuri Andropov, the KGB Chairman, to full membership (having served as a candidate member since 1967).

[30] Defense ministers who had served in the Politburo are Leon Trotsky, Mikhail Frunze, Kliment Voroshilov, Nikolai Bulganin, Georgy Zhukov and Dmitry Ustinov among others.

[32] For comparison, according to the population censuses, during these years the Soviet Union had a composition of between 51% (in 1989) and 58% (in 1939) Russian, between 15% (in 1989) and 21% (in 1926) Ukrainian, between 1.2% (in 1926) and 1.4% (in 1989) Georgian, and between 0.5% (in 1989) and 1.8% (in 1926) Jewish.

[36] Only four women ever served in the Politburo; Elena Stasova, Yekaterina Furtseva, Alexandra Biryukova and Galina Semenova.

[37] Furtseva, Biryukova and Semenova reached the Politburo under the leadership of reformist party leaders; Nikita Khrushchev and Mikhail Gorbachev.