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Alliance and non-aggression pacts are the two most common forms of pacts between rulers. A non-aggression pact is an agreement between two rulers simply to not declare war on the other. An alliance is an improved pact based on an existing non-aggression pact and is more powerful allowing rulers to be called to war.

Non-aggression pacts[edit]

A non-aggression pact is an agreement between two rulers not to attack each other. Most non-aggression pacts are created by a marriage or betrothal:

  • Characters always have a non-aggression pact with their spouse.
  • When two rulers negotiate a betrothal or marriage involving close relatives, they automatically form a non-aggression pact.
  • Two rulers can negotiate a non-aggression pact based on a existing marriage involving their close relatives.

A non-aggression pact between a vassal and a liege prevents the liege from revoking the vassal's titles, and prevents the vassal from joining or creating a faction. Also a ruler with a non-aggression pact with another ruler, cannot be called to arms by an ally in an offensive war against that ruler.


Alliances are additional agreements to call each other into most wars.

Form alliance[edit]

  • Must be a close relative OR have a non-aggression pact
  • Cannot form alliances with your vassals or your lieges
Factors Tooltip Description
Opinion +10 to -10?
Same Dynasty +2
Same Interests +2
Common Enemies +2
Political Concerns -1 or more? Often means they have a CB against you. Oddly, this malus applies even when negotiating an alliance atop a non-aggression pact.
Base Reluctance -3 -25 (if this is the only factor other than opinion, need 26 opinion for Yes)

Call to arms[edit]

See also: Diplomatic_actions#Call_to_arms

Alert alliance.png Rulers are expected to accept calls to arms with any rulers they have an alliance with. Rulers may also receive call to arms from fellow rulers who have the same culture who are defending themselves from another culture. Nomadic and tribal vassals can also receive call to arms from their liege, as can tributaries and suzerains.


  • Faction rebellion leaders cannot call in allies, except for claimant rebellions.
  • When fighting a fellow vassal, can only call in other rulers with the same liege. (Exception: if the "fellow vassal" is a faction rebellion against you, can call allies from other realms!)
  • Cannot call vassals of your enemy, except in "revolt against tyranny" wars
  • Cannot call allies into an offensive war in which a ruler has a non-aggression pact with the defender.
  • Can call both a liege and their vassal, if you're allied with both, but it only works properly if you call the liege first.

Accepting or declining[edit]

Declining a call to arms in an alliance costs a large amount of prestige and marks you as an Alliance Breaker.

Declining other calls to arms has a minor prestige cost:

  • -25 prestige for a offensive war.
  • -100 prestige for a defensive war.
  • 0 if the belligerents are allies.
  • 0 for a suzerain declining a tributary's call to arms.

See also[edit]

  • Defensive pact - Special pacts created to combat threatening characters.
  • Tributary - a relationship created through use of the use of the tributary casus belli.
  • Rules of Engagement - Dev diary discussing major changes alliances and the introduction of non-aggression pacts.
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