AdvanceChanged this version
Zasechnaya Cherta
In order to withstand the constant threat of Tatar raids, our ancestors have built a line of tightly positioned and well-defended forts. As our state grows larger, we should keep expanding this 'Abatis Line' to ensure our people are always protected from foreign attacks.
MuscovyCountrypotentialAdvance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Reformation tree itself.
Modifiers
Definitionin_game/common/advances/country_MOS.txt:48
49content_priority = 1000