Assistance in war and diplo modifiers - how works?

[Brichals]

I have something that puzzles me and I think from reading comments from others it may be an(other) largely ambiguous part of diplomacy.

When a friend asks me for assistance in war I might join. Then I might take a city from the enemy within 5 turns say, and then they offer me a very good peace treaty deal. So I accept. But the person who proposed the war is still at war.

Does the AI get annoyed by this behaviour. I just jumped on his war to claim maybe a nice border city and take a good peace treaty deal and then left my ally to it. Is this why often your allys can turn around after a shared war and start to hate you?

My question is, when engaging in a joint war, do you have to keep war for a certain length of time (I think it may be 10 turns but not sure). Or should I only make peace when my ally does? Or does it not matter at all?

 

[Strategist83]

Your 'war ally' doesn't care at all if you contribute to the war or not. He also doesn't care whether you make peace at first opportunity, possibly without having ever even met with the enemy.

The only way to piss off your ally is if you do a real good job and 'destroy' the enemy civilization by claiming all their cities. You can take all their cities except one without problems, but the moment you 'destroy' a civ, all hell breaks lose and you can expect your 'ally' along with the rest of the known world to instantly denounce you, with following poor diplomatic relations for the entire remainder of the game.

Your ally thus didn't become upset because you didn't help in his war, but because you now have cities bordering his cities - those you and he conquered. Once he is thus angered with you, he may also start to think you are a warmonger - just to add to the hate - even though you fought on the same side and possibly on his request.

This may all sound really dumb, but it's just the way the AI works.

 

[Glassmage]

There is no more you are warmonger negative anymore if you have DoF with an AI. Instead you get positive "we fought common foe". Only when your friendship turn sour and AI is Guarded then that "they believe you are warmonger menace" thing will come up. Even then the positive "fought common foe" can still exist.

 

[Keejus]

^Friendly AI, even if they're not deceptive, will hide the non-global negative modifiers they do have against you. You won't ever see a friend saying they covet your lands or wonders, either.

According to the patch notes the more damage you do fighting a common foe, the greater that modifier will be. You still build warmonger hate, so someone like Gandhi might still hate you after a common war, but if you trash someone together with Genghis Khan or Harald Bluetooth, you might make a friend for life.

Two of the biggest warmonger modifiers, to my awareness, come from razing and wiping out civilizations. You can get away with some in the eyes of most leaders, but if you burn down everything in your path, not even your allies will trust you

 

[Strategist83]

What Glassmage says is unfortunately incorrect; waging wars - more specifically, 'destroying' civilizations (even if it's just a city-state, it still counts as a civ) will get even your best friends to denounce you in short order. You may get away with a single 'destruction' if you have a DoF with somebody but everybody else will insta-hate you and your friends will hate you as well when you destroy your 2nd civ. Civ destruction = guaranteed collapse of diplomatic relations. Which is why attacking city-states is so darn counter-productive - a very unfortunate mechanism.

Unlike Keejus, I don't believe there is any sort of penalty for razing cities.