So, in the latest game play I am doing now, I got "drug" into a war because of an ally civilization.  And that is fine and all, but it definitely exposed a few weaknesses in the design.  First, if my ally is going to get the opportunity to file for a grievance because he jumped into war without even sending a note to say he was going to do it - then I should be able to file a grievance against them (my ally) for pulling me into their trouble.  
That's just the little thing though, the bigger issues are with how you can extract yourself from the war.

So... My Ally, decided to extract themselves from the war he was in with one civilization, so that they could engage in a war with a different civilization... Ok fine... I should be wondering if they are the right ally to have at this point. But by this time, I had already joined in to the fray and between the two of us, we had regained all the ground previously lost to their aggressor. (and had them on the ropes, ready to start taking their territory.) However, without even a by-your-leave, my ally decides to concede his first fight for territory near his capital for a fight 1/2 a continent away. And in doing so, gave away the territory they had just won back as a war penance, I assume.
Now, that would have been fine by me, I could have just let it go at that point, but... I couldn't.  You see, there was no way to actual end my declaration of war with the 1st combatant.  Unless, of course I just said: I-surrender.  The option for a 'white-peace' was not available.  I had filed two grievances against whom I assumed was the aggressor attacking my ally.  So, the white-peace option only is available if both of us had grievances against the other...  Really?  What?  
They were losing, mostly but not quite war weary - then my idiot ally decides to change their mind in the middle of a war - and now I can't even get out of it?  I mean, yes, I know AI's are stupid... but... well, shiester, but nothing I guess...
Really?  I have to actually pound them into the dirt before they will say it's ok to stop?
And then, to top it all off, my ally, who is now not at war with the first party, is now upset with me that I don't surrender like they did?  They are going to start backing out of the alliance and rescinding treaties?  While they have armies on my territory preparing to attack my districts?  Sorry - I am taking them out, period.

so, there really needs to be a few upgrades here: 
First, communication between allies needs some real improvement.  I would say that you make a 'war' screen for allies.  Status update on both allies, and perhaps a vote-to-end, or at least a notification that they intend to extract themselves.  (prior to, of course)

Second, the information should allow me to see who started the war.  Did my Ally?  And I could just take it out on them with the treaties we have?  Or were they (my ally) righteously the aggrieved party.  I should be able to see the grievances that are held between my ally and the other party.  Those grievances are actually very informative, why can I not see my allies status on those?

Third, if I got drug into a war because of my ally, I should be able to sue for a white-peace, regardless of if the other party has any grievances against me.  If they have any meaningful war-weariness at all, say less than 35% population support, they should accept that we can call it a draw.  No concessions needed.

Fourth: how in the world am I supposed to be able to 'forgive' a grievance?  I can't figure it out.  My ally forgave one of my grievances they had and I got a notice about it.  So, perhaps that is because they never actually claimed it against me.  Regardless, I don't see that option for me on my screen.  All I have is the option to ignore what is on the list for 10 turns, no option for dismal.  And while that is fine for most of them, when your in a war with someone, its not quite good enough.  I claimed two grievances before I joined the fray, thinking that I could influence any early end to the war between them.  (at that point, before I became a combatant.)  But I should be able to remove them in the war-resolution screen and give it a shot at ending the war without a full blown surrender.  There needs to be a better conflict resolution system in-place.

Fifth: Even if I cannot resolve the conflict with my Allies last enemy, they should not hold it against me that I am unwilling to just surrender and go join them in their next war.  The AI algorithm's should have some turn tolerance forgiveness in demoting treaties.  Say 10 to 15 turns.  It could be tied to the personality traits: traitorous, loyal, what-not.  And modified by the length we have been allies.  But really, 1 turn after they surrender, they expect me to?  While I am still under threat?  That is obscene.  

sixth: perhaps a 'war-progress' monitor could be added during times of war to help present and access the information would be useful.  graded on units lost, population support of the combatants, whom is engaged, etc..  Just a thought.

anyway...  I really do like the war mechanic you have introduced, but the whole ally & enemy engagement/information thing really needs to be addressed.  I do hope this helps solicit some thought and feedback.

PS:  Oh, and the calculations about whether or not an AI is willing to end one war to begin another, really need to be looked at again.  giving away a terriroty physically connected to the capital city is no where near as important as keeping a dispersed territory with minimal resources.

It's "dragged" not "drug".