Casus Belli (CB) #

A Casus Belli (“justification for war”) enables you to Declare War without receiving a -2s penalty. The following CBs can be obtained.

Conquest (Claim) #

Having a Claim (G) on an Area provides a CB against all other Realms that currently Own Provinces in that Area.

Call to Arms #

A CtA (see p. 32) in itself constitutes a CB on your Ally’s new Enemy. This CB is lost immediately if the CtA is refused.

A Defensive CtA lets you ignore all DoW restrictions (like Truces, conflicting Alliances, etc.) when accepting the Call.

General CB (CB token) #

Some situations will provide you with a temporary CB, indicated with a CB token on the target’s Capital.

You get a CB against any Ally that refuses to honor your CtA. You may also get such a CB from an Event.

CB tokens are removed from the board in Phase 3, Step A (see p. 9).

Event #

An Event that lets you Declare War on another Realm is always a CB in itself.

This CB also negates the -1s penalty for a DoW on a Marriage partner.

Disputed Succession #

A M which is displaying its “Disputed Succession” (L) side provides a CB for all PRs against the Realm on which the token is placed.

This CB also negates the -1s penalty for Declaring War on a Marriage partner. Furthermore, if you have a Marriage with the target, this CB lets you Declare War even during an Interregnum or if the target is your Ally (or both). If used to Declare War on an Ally, the Alliance ends.

Additionally, a L provides a CB on all PRs at War with the target Realm.

Excommunication #

If your Realm is Catholic, and the Curia controller has Excommunicated the Ruler of another Realm, you have a CB against that Realm for as long as the Excommunicated token is in play (see p. 46). This token is removed during Phase 4, Step E.

Holy War (Crusade) #

With the “Deus Vult” Idea, you have this CB against all adjacent Realms with a different State Religion than yours, including any Distant Realm, with the notable exception that PRs with a Christian State Religion cannot use it against other Christian Realms.

If your Realm is Catholic, you get this CB against Realms that are currently the target of a Crusade (see p. 46). When using this CB to Declare War on a Crusade target, place one of your Tag chits on the Committed to Crusade slot on the Status Mat. The Crusade token is removed in Phase 4, Step E.

Imperial Liberation (HRE only) #

The Emperor has a permanent CB against any Realm with their Capital located outside the HRE that Controls Provinces or has Vassals located inside the HRE.