Perestroika is an ambiguous concept. The term was chosen by Mikhail Gorbachev partly because the word "reform" had been taboo in Soviet ruling circles ever since the "Prague Spring" of 1968, the unfolding of which also put paid to Aleksei Kosygin's modest attempt to reform the Soviet economy. Gorbachev had used the word perestroika in speeches and writings on a number of occasions even before he became General Secretary of the Central Committee of the Communist Party of the Soviet Union (CPSU) in March 1985. What he meant by it, however, changed over time, especially during the period of less than seven years in which he was Soviet leader. In 1985 he believed that the Soviet system was reformable and "perestroika" was for him essentially a synonym for reform. The imprecision of the word had the initial advantage that almost everyone could be in favour of perestroika because they meant so many different things by it. In retrospect, conservative Communists felt they had been hoodwinked. Given their political outlook, they should have opposed the reforms of the perestroika era more vigorously and earlier than they did. They were kept on board not only by the hierarchical nature of Soviet politics and the power and authority which accrued to the general secretaryship. What also wrongfooted them was Gorbachev's success in establishing the dividing line in Soviet politics as lying between a pro-perestroika progressive majority and a reactionary anti-perestroika minority.