A reason to fight
War without a casus belli brands you an aggressor and bleeds your legitimacy — so before you march, get a pretext.
How it works
casusBelli() checks a priority ladder for any valid reason to fight: an active rivalry, deep hostility (relations at or below −50), recent espionage against you (wronged), a fabricated pretext, an ally already at war, reconquest of breakaway or lost land, an irredentist historical claim, or consolidation of an isolated newly-freed neighbor. The first match becomes your CB.
If none of these apply, declareWar() fires the aggressor penalty: approval −8, stability −6, reputation −12, leader legitimacy −10, and every neighbor in your subregion cools by −8. A 'consolidation' CB is far milder — just −2 with each neighbor and no home backlash.
You can manufacture a reason. The 'Fabricate pretext' spy op (needs infiltration 60) plants a fabricated CB that stays valid for 48 ticks (1 year). For the AI this is decisive — a standing fabricated pretext multiplies its war-declaration probability by 5×, so a fabricated CB is a genuine early warning that an attack is imminent.
Formulas
relations ≤ −50 → 'hostile'valid while (tick − pretextTick) < 48 (1 year)chance × (pretext ? 5 : 1)Key numbers
How to play
- ▸Sink relations to −50 or below (sanctions, rival-marking) to earn a free 'hostile' CB before declaring.
- ▸Reconquest and irredentist claims carry almost no penalty — reclaiming breakaway or historically-held land is the cleanest war goal.
- ▸If a rival fabricates a pretext on you, treat it as a countdown: their attack odds just jumped 5×, so mobilize or seek allies now.
- ▸Watch for isolated states freed within the last 8 years with no allies — they qualify for a low-notoriety 'consolidation' CB.