AIs declare "Formal War" with no CB

[CD7]

My basic understanding was without a CB, a player has to denounce you first, wait 5 turns and declare Formal War? However this is not happening.
I don't know if its a bug in the mechanics, or just a labelling issue? (eg says "Formal War" when it should say "Surprise"?)

 

[Gyrofalcon]

A Surprise War is no Formal War, and no need for CB. And the AI have the same CB rules to follow.
In late game, the AI can declare colonial or religious war, etc

 

[CD7]

A Surprise War is no Formal War, and no need for CB. And the AI have the same CB rules to follow.
In late game, the AI can declare colonial or religious war, etc

???

 

[Leyrann]

What I have seen happening in my games, is that if the AI declares a joint war (even if they have no casus belli) it counts as a formal war, which is probably what OP is talking about too. And it's not what's supposed to happen; just because you're declaring war with two civs together doesn't mean it's not a surprise war anymore.

 

[erikvv]

Can confirm this still takes place in 1.0.0.129. When 2 AI's declare on you at the same time it is announced as a formal war, and no denouncement had taken place.

 

[Rosty K]

Joint War counts as Formal War, CB or not.

 

[Piruparka]

Yes, it kind of is a CB. To be honest though, I don't like this. To me, this happens in almost every game that very early on, the first to civs I meet will declare a joint war on me soon.