In Civilization 6, are you allowed to make a declaration of war against someone that you have a formal friendship relationship with?

  • 2
    I suspect you could easily answer that question yourself. Just save the game, try and declare war against your friend, and if necessary load the previous save.
    – Nolonar
    Dec 30, 2016 at 22:13

3 Answers 3


Yes, you can declare war on friends. Of course this will be met with diplomatic penalties such as warmongering and denouncing, but nonetheless you can do it.

EDIT: As tubes pointed out, you cannot declare war on Allies.

  • 1
    This answer is partially incorrect. You can declare a surprise war on declared friends but NOT allies. I recently had to wait for an alliance to expire before I could capture the final remaining capital to win a Domination victory. Surprisingly I was even able to nuke the capital but the ally remained non-hostile and I was unable to attack it with units until I could declare war. civ6.gamepedia.com/Alliance
    – user131854
    May 16, 2017 at 17:36
  • My bad, I thought that was because it was a multiplayer game where we were on the same team. I don't think I've ever had an ally other than that.
    – Shelby115
    May 16, 2017 at 20:54

I don't think the accepted answer is true anymore. I want to attack a civilization (a declared friend, not an ally) which is attacking an allied city state, but I am unable to declare a surprise war:

Cannot declare surprise war

Could this have been changed in a later patch?

Whether or not it is possible to declare war using a causus belli I do not know.

  • i just got this as well
    – cryanbhu
    Mar 14, 2023 at 23:02
  • Allies (have Flags icon) - can’t cause war
  • Declared friend (have Cyan smiley icon) - can’t cause war
  • Friend (have Green smiley icon) - can cause war

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