During the century and a half since 1850 Russia experienced a wider range of political change than any other European state. Until 1906 the political system was based on autocracy, which survived, in theory if not in practice, until March 1917. Between October 1917 and the end of 1991 the official ideology was Marxism-Leninism, usually referred to as Communism. For a brief period, between March and October 1917, Russia experienced less extreme alternatives in the form of moderate socialism and liberal democracy. Both of these had opposed autocracy but, through their failure to achieve a permanent cooperation after its downfall, let in a system that was to dominate the twentieth century.