What is the default Chance of Frankokratia game rule in CK3?

Balanced: The Splintered Crusade, diverting Catholics to attack Byzantium, is immediately possible from the 1178 start date. If using an earlier start, this can happen only after the first Catholic Crusade. (patch 1.20.1.2)

Does changing the Chance of Frankokratia rule disable achievements?

No: none of its 4 settings carries the flag blocks_achievements in patch 1.20.1.2.

Game rule · Historicity · Difficulty

Chance of Frankokratia

Balanced · default
None
Fourth Crusade
High

Chance of Frankokratia is a game rule in Crusader Kings III (Historicity and Difficulty) with 4 settings: Balanced (the default), None, Fourth Crusade and High. None of its settings disables achievements. Patch 1.20.1.2, from game/common/game_rules/00_game_rules.txt.

This section as JSON: /raw/game-rules.json

Quick answers (2)

What is the default Chance of Frankokratia game rule in CK3?: Balanced: The Splintered Crusade, diverting Catholics to attack Byzantium, is immediately possible from the 1178 start date. If using an earlier start, this can happen only after the first Catholic Crusade. (patch 1.20.1.2)
Does changing the Chance of Frankokratia rule disable achievements?: No: none of its 4 settings carries the flag blocks_achievements in patch 1.20.1.2.

4 settings

Balanced
Default
The Splintered Crusade, diverting Catholics to attack Byzantium, is immediately possible from the 1178 start date. If using an earlier start, this can happen only after the first Catholic Crusade.
The script checks it once, in 1 place
Scripted triggers 1
- ep3_frankokratia_ghw_trigger
Every has_game_rule = historicity_frankokratia_default in game/common and game/events, by the top-level object it sits in.
historicity_frankokratia_default
None
Catholic Crusaders will not be diverted to attack the Byzantine Empire.
The script checks it once, in 1 place
Scripted triggers 1
- ep3_frankokratia_ghw_trigger
Every has_game_rule = historicity_frankokratia_blocked in game/common and game/events, by the top-level object it sits in.
historicity_frankokratia_blocked
Fourth Crusade
From earlier start dates, at least 3 Catholic Crusades must happen before the Splintered Crusade. From 1178, Catholics may attack Byzantium only after 1 Crusade.
The script checks it once, in 1 place
Scripted triggers 1
- ep3_frankokratia_ghw_trigger
Every has_game_rule = historicity_frankokratia_fourth_crusade in game/common and game/events, by the top-level object it sits in.
historicity_frankokratia_fourth_crusade
High
Any Catholic Crusade can become a Splintered Crusade, breaking apart to launch a war against Byzantium.
historicity_frankokratia_high

Source: game/common/game_rules/00_game_rules.txt line 1544 (key historicity_frankokratia), modifiers from game/common/modifiers, names from the English localisation; Crusader Kings III 1.20.1.2.