The term 'Old Russian Autocrat' refers to a TSAR or CZAR, which were titles used by the monarchs of Russia from the 15th century until the Russian Revolution in 1917. A TSAR was the title used by the rulers of the Grand Duchy of Moscow and later the Tsardom of Russia and the Russian Empire. A CZAR was the title used by the rulers of the Tsardom of Bulgaria and the Tsardom of Serbia. Both titles were used interchangeably to refer to the same position of absolute power.