The founding and development of the agency was intertwined with the career of its founder, Yuri Levada — the first professor to teach sociology at Moscow State University. During the political thaw initiated by Nikita Khrushchev, Levada was allowed to carry out limited surveys of public opinion. In one lecture, Levada asserted that tanks could not change ideologies, a reference to the Soviet invasion of Czechoslovakia in 1968. However, his first conflict with those in power came from a survey asserting that few actually read "Pravda"s notoriously longwinded editorials; and "Pravda" quickly and bitterly denounced the sociologist. In 1972, his institute was closed down during a Brezhnev-era purge of some 200 sociologists from research institutes and universities.