The Old Believers or Raskolniki became separated after 1666 from the official Russian Orthodox Church as a protest against church reforms introduced by Patriarch Nikon between 1652 and 1666. Old Believers continue liturgical practices which the Russian Orthodox Church maintained before the implementation of these reforms. Mussorgsky’s Khovanshchina is about the Old Believers’ rebellion, with the help of the Streltsy, against Peter the Great.
In the eyes of these Raskolniks the Tsar Peter’s version of Orthodoxy was no Orthodoxy at all; and yet at the same time it was impossible to imagine the old ecclesiastical order triumphantly reasserting itself in the teeth of a secular government that was now omnipotent as well as Satanic. The Raskolniki were therefore driven to hope for something which had no precedent, and that was for the epiphany of a Tsar-Messiah who would be able as well as willing to undo the Tsar-Antichrist’s sacrilegious work and restore the Orthodox Faith in its pristine purity because he would combine absolute mundane power with perfect piety. The Raskolniki hugged this wild hope, because their only alternative was the bleak prospect of waiting grimly for the Last Judgement.
A Study of History, Vol VI, OUP, 1939