In the Czech lands (included in Czechoslovakia until the end of 1992), rock music has evolved through three phases. In the first phase, lasting until 1968, rock musicians had no ambition to offer social or political commentaries. This began as the era of rock ‘n’ roll, which is to say music being performed for dancing. The second phase began after the Soviet bloc invasion of Czechoslovakia in August 1968, lasting until the end of the communist era in 1989. In this phase, rock musicians (no longer playing rock ‘n’ roll were closely monitored by the authorities and were expected to sing happy songs, submitting their song texts to the authorities for approval in advance of performing them. In spite of this control, some rock groups purposefully sang political texts in the 1970s and 1980s, mocking or criticizing the communists, albeit often cryptically. Finally, in the third phase — since 1989 — having lost their ideological foe, Czech rock groups have for the most part become politically disengaged.