Answer by taking a quote from the following article:

Andrei Dmitrievich Sakharov (Russian: Andrei Dmitrievich Sakharov; 21 May 1921 - 14 December 1989) was a Russian nuclear physicist, dissident, and activist for disarmament, peace and human rights. He became renowned as the designer of the Soviet Union's RDS-37, a codename for Soviet development of thermonuclear weapons. Sakharov later became an advocate of civil liberties and civil reforms in the Soviet Union, for which he faced state persecution; these efforts earned him the Nobel Peace Prize in 1975.

In 1972 Sakharov became the target of sustained pressure and intimidation, from his fellow scientists in the USSR Academy of Sciences, the Soviet press and direct threats of physical assault. Dissident activists, including the writer Aleksandr Solzhenitsyn, sprang to his defence.  In 1973 and 1974, the Soviet media campaign continued, targeting both Sakharov and Solzhenitsyn. While Sakharov disagreed with Solzhenitsyn's vision of Russian revival, he deeply respected him for his courage. Only a few individuals in the Soviet Union were willing to defend 'traitors' like Sakharov and Solzhenitsyn, and those who had dared were inevitably punished.  Sakharov later described that it took "years" for him to "understand how much substitution, deceit, and lack of correspondence with reality there was" in the Soviet ideals. "At first I thought, despite everything that I saw with my own eyes, that the Soviet State was a breakthrough into the future, a kind of prototype for all countries". Then he came, in his words, to "the theory of symmetry: all governments and regimes to a first approximation are bad, all peoples are oppressed, and all are threatened by common dangers."  After that he realized that there is not much "symmetry between a cancer cell and a normal one. Yet our state is similar to a cancer cell - with its messianism and expansionism, its totalitarian suppression of dissent, the authoritarian structure of power, with a total absence of public control in the most important decisions in domestic and foreign policy, a closed society that does not inform its citizens of anything substantial, closed to the outside world, without freedom of travel or the exchange of information." Sakharov's ideas on social development led him to put forward the principle of human rights as a new basis of all politics. In his works he declared that "the principle 'what is not prohibited is allowed' should be understood literally", defying the unwritten ideological rules imposed by the Communist ruling elite on the society in spite of the seemingly democratic (1936) USSR Constitution.  In no way did Sakharov consider himself a prophet or the like: "I am no volunteer priest of the idea, but simply a man with an unusual fate. I am against all kinds of self-immolation (for myself and for others, including the people closest to me)." In a letter written from exile, he cheered up a fellow physicist and human rights activist with the words: "Fortunately, the future is unpredictable and also - because of quantum effects - uncertain." For Sakharov the indeterminacy of the future supported his belief that he could, and should, take personal responsibility for it.

did you find anything interesting?
In 1973 and 1974, the Soviet media campaign continued, targeting both Sakharov and Solzhenitsyn.