Belief

 In 17th century Russia Old Believers

 unmoved in the tumult of doctrinal change

 intransigent in their long-held beliefs

 insisted on pronouncing Alleluia three times, not twice.

And, conversely, crossed themselves with two fingers, not three.

Made their processions round a church clockwise, not counterclockwise.

Accordingly, Czar Peter created an Office of Schism to hunt them down.

Which scattered them to Sierian taiga and foreign lands

- the better to maintain these essential beliefs