Alexander Yakovlev, who has died aged 81, was one of the main proponents of perestroika, the restructuring of the Soviet Union which took place so spectacularly during the 1980s.
Yakovlev was in charge of ideology in the Politburo in the 1980s
With his bushy eyebrows and large jowls, Alexander Yakovlev was often to be seen behind Mikhail Gorbachev, most notably at the Soviet leader's five ground-breaking summit meetings with Ronald Reagan.
As well as advising Gorbachev on foreign affairs, Yakovlev was the prime mover behind glasnost - or openness - and perestroika - restructuring - which transformed the Soviet Union.
Alexander Nikolayevich Yakovlev was born in the village of Korolyovo, in the Volga River Yaroslavl region, in 1923.
After serving in the Red Army in World War Two, and being badly wounded in 1943, he graduated from the history faculty of Yaroslavl University and became a Communist Party apparatchik.
Yakovlev's rise was heavily influenced by the liberalisation of Russia by Nikita Khrushchev in the late 1950s which ended the Soviet Union's isolation from the outside world.
Political soulmate: Mikhail Gorbachev
And he was among a handful of Soviet pioneers who were allowed to spend a year studying foreign relations in the United States in 1958-59.
Proof of his trustworthiness came when he was appointed Soviet ambassador to Canada in 1973.
It was during his decade in Ottawa that he first met Mikhail Gorbachev, when the latter was a visiting member of the Politburo during the early 1980s. It was to be the start of an extraordinary and vastly important political partnership.
"We discussed everything," Yakovlev later recalled. "We interrupted each other and said 'That thing must be changed and that one's intolerable... everything's intolerable'."
After Gorbachev became Soviet leader in 1985, he quickly placed Yakovlev in a number of influential posts.
In 1987, Yakovlev became a full member of the Politburo, overseeing ideology and propaganda.
And he played a key role in Gorbachev's efforts to encourage media freedom.
All the while, Yakovlev fought against the diehard wing of the Communist Party.
Much to its fury, he succeeded in revealing the secret annex to the 1939 Molotov-Ribbentrop pact, the treaty between the Soviet Union and Nazi Germany which led to the Soviet annexation of the Baltic nations and the division of Poland.
He also actively contributed to Gorbachev's efforts to reform the Soviet Union, reducing the Communist Party's role and encouraging the development of
a multi-party system.
After the fall of the Soviet Union, Yakovlev became head of the commission for rehabilitation of victims of Soviet political repression, revealing for the first time the full extent of the horrors of the Stalin era.
In 2000, Yakovlev attracted world attention by contending that the Swedish diplomat, Raoul Wallenberg, had been shot by the Soviet secret police in 1947.
Wallenberg helped to save thousands of Jews in Hungary in the waning months of World War II, but disappeared after Hungary was occupied by the Red Army.
Yakovlev later established the International Democracy Foundation, which he chaired until his death.