Stalin died in 1953, and on 20 March 1959, Kosygin was appointed to the position of chairman of the State Planning Committee (Gosplan), a post he would hold for little more than a year.

[4][5][6] In addition to managing the Soviet Union's economy, he assumed a preeminent role in its foreign policy by leading arms control talks with the US and overseeing relations with Western countries in general.

[7] However, the onset of the Prague Spring in 1968 sparked a severe backlash against his policies, enabling Leonid Brezhnev to decisively eclipse him as the dominant force within the Politburo.

[13] When asked why he worked in the co-operative sector of the economy, Kosygin replied, quoting a slogan of Vladimir Lenin: "Co-operation – the path to socialism!

"[14] Kosygin stayed there for six years until Robert Eikhe personally advised him to quit, shortly before the repressions hit the Soviet consumer co-operation movement.

Stalin shared information with Kosygin, such as how much money the families of Vyacheslav Molotov, Anastas Mikoyan, and Lazar Kaganovich possessed, spent and paid their staff.

In June 1957, he was again appointed a Deputy Chairman of the Council of Ministers (for the third time), and a candidate member of the Presidium Central Committee (the renamed Politburo).

[27] When Khrushchev was removed from power in October 1964,[28] Kosygin replaced him as Premier in a collective leadership that included Leonid Brezhnev as general secretary and Nikolai Podgorny who ultimately became Chairman of the Presidium.

Kosygin, Podgorny and Andrei Kirilenko were the most reformist members, Brezhnev and Arvīds Pelše belonged to the moderate faction while Mikhail Suslov retained his leadership of the party's Stalinist wing.

Examples include the handling of the Prague Spring and the later Soviet invasion of Czechoslovakia[30] (which Kosygin initially resisted),[12] the decline in agriculture production, the Sino–Soviet border conflict[30] (he advocated restraint),[12] the Vietnam War, and the Soviet–American talks on the limitation of strategic missiles.

By March 1971, it became apparent that Brezhnev was the leader of the country, with Kosygin as the spokesman of the five-year plan and Podgorny's position within the collective leadership strengthened.

[38] Relations between the two countries improved further when the 1970 Moscow Treaty was signed on 12 August 1970 by Kosygin and Gromyko and Willy Brandt and Walter Scheel who represented West Germany.

[39] In 1971, Kosygin gave an extensive interview to the American delegation that included David Rockefeller, presenting his views on US-Soviet relations, environmental protection, arms control and other issues.

[43] Kosygin protected János Kádár's economic reforms and his position as leader of the Hungarian People's Republic from intervention by the Soviet leadership.

[44] Polish leader Władysław Gomułka, who was removed from all of his posts in 1970, was succeeded by Edward Gierek who tried to revitalize the economy of the People's Republic of Poland by borrowing money from the First World.

The Soviet leadership approved both countries' respective economic experiments, since it was trying to reduce its large Eastern Bloc subsidy programme in the form of cheap oil and gas exports.

[48] The Sino–Soviet split chagrined Kosygin a great deal, and for a while he refused to accept its irrevocability; he briefly visited Beijing in 1969 due to increased tension between the USSR and Maoist China.

[30] At the 23rd Party Congress Kosygin promised that the Ninth Five-Year Plan would increase the supply of food, clothing and other household appliances up to 50 percent.

[53] The plan envisaged a massive increase in the Soviet standard of living, with Kosygin proclaiming a growth of 40 percent for the population's cash income in his speech to the congress.

Following this sudden decrease, housing construction increased sharply between 1965 and 1966, but dropped again, and then steadily grew (the average annual growth rate was 4.26 million square metres).

[64] Kosygin initiated another economic reform in 1973 with the intentions of weakening the central Ministries and giving more powers to the regional authorities in republican and local-levels.

According to historian Ilya Zemtsov, the author of Chernenko: The Last Bolshevik: The Soviet Union on the Eve of Perestroika, Kosygin "began to lose power" with the 24th Party Congress in 1971 which for the first time publicized the formula 'the Politburo led by Brezhnev'".

[68] Kosygin was hospitalized in October 1980; during his stay he wrote a brief letter of resignation; the following day he was deprived of all government protection, communication, and luxury goods he had earned during his political life.

At the end of his life, Kosygin feared the complete failure of the Eleventh Five-Year Plan (1981–1985), saying that the sitting leadership was reluctant to reform the stagnant Soviet economy.

[74] A state funeral was conducted and Kosygin was honoured by his peers; Brezhnev, Yuri Andropov, and Tikhonov laid an urn containing his ashes at the Kremlin Wall Necropolis.

[75] In a description given by an anonymous high-ranking GRU official, Kosygin is described as "a lonely and somewhat tragic figure" who "understood our faults and the shortcomings of our situation in general and those in our Middle East policy in particular, but, being a highly restrained man, he preferred to be cautious."

[71] Singapore Prime Minister Lee Kuan Yew remembered Kosygin as "very quiet-spoken, but very determined, mind of great ability and application".

While Leonid Brezhnev was content to maintain the centralized structure of the Soviet planned economy, Kosygin attempted to revitalize the ailing economic system by decentralising management.

Following Brezhnev's death in 1982, the reform movement was split between Yuri Andropov's path of discipline and control and Gorbachev's liberalization of all aspects of public life.

[84] During a state visit to Peru in the 1970s with Leonid Brezhnev and Andrei Gromyko, all three were awarded the Grand Cross of the Order of the Sun by President Francisco Morales Bermúdez.