Accepting capitulation is a guarantee that you will spare them in exchange for their service. If you can just arbitrarily cancel at any time, there's no reason they'd ever accept it from a gameplay point of view. It is the same logic as peace treaties. There's no logic to accepting a peace treaty if you can just break it again even though there's no real reason why you can't tear up that piece of paper.
The first thing that comes to mind is, you take a vassal in capitulation. Then find out you never wanted that vassal so you cancel the deal...
Now, there are two ways this could go:
- You are the one cancelling the vassal.
- You suffer a +2
penalty in all your cities for X number of years. "The lack of political stability makes us angry!"
- You suffer a -4 to diplomatic relations with your previous vassal. "We are upset that you broke the terms of surrender with us!"
- You suffer a -1 to diplomatic relations with all civs that have positive relations with the previous vassal. "You abused a capitulation vassal agreement."
- If you then declare war on your previous vassal within X years you suffer another:
- +1
penalty in all cities for X number of years. "You are seen as a villain by the world!"
- -2 to all diplomatic relations. "Your war on a capitulated nation have proven your bad nature to us!"
- They are the ones cancelling the vassal.
- They suffer a +2
in all their cities for X number of years. "We think you lost your mind."
- They suffer a -3 to all diplomatic relations. "You broke a capitulation agreement"
- You are now allowed to (free of any repercussions) engage in war with that civ again should you decide to do so.
Why a capitulated vassal would break the agreement is beyond me but perhaps he "just doesn't like you enough" (<= -10 diplomatic relations?) and they'd rather fall to oblivion than be slaves to your nation.
Though there is one method to "absorb" a vassal. And that is via culture and espionage. Under the table and "pressure" the poor guy into oblivion. There's many real life examples of this where a conquered people become assimilated into the conqueror's culture and cease to be recognized as a nation.
Yeah, lets culture him to death after having had him as a vassal for the rest of the game... His last city was a colony on the other side of the continent with lots of tundras and no good resources to get a culture city started. I might as well plant cities and give them to him. Not that it would matter since within 5 tiles where the other power blocks cities and that would just spark "close borders cause tensions" and then they would declare war on me/him because of that.
And even from the point of realism, that bonus war is not really an issue. Why shouldn't they seek the protection of another power, especially one that sees that it may be a good idea of attacking you?
The same reason i wouldn't take a vassal that would do more harm than good.
I admit i never read the full terms of surrender in the first place, had i known he would become an unbreakable vassal to me i would have opted to keep the war going until i could conquer a coastal city and then sent one galley to finish him off.
The reason i killed him off to begin with was that he kept declaring wars on me despite him having a 1:2 power ratio with me and always lost his attacking force within 4 turns of the war declaration. I was simply fed up with him so i razed all cities in sight.
This is instituted in the game as defensive pacts. You pledge to take military actions only if someone else instigates it. However, my statement is that if your "friends" are clearly aligning themselves with a hostile empire that intends to encroach on you, it may be time to find better friends.
Like i said, i wanted to play a game where i never had to fight someone else's wars but could use my power to ensure my friends never fall. Hence why i had such good relations with them to begin with as i had provided them with strategic resources and units every time they where in war time. It's just one more aspect of the game missing which just makes other aspects of the game incomplete IMHO.
If you have a +16 in diplomatic relations i don't see how that doesn't constitute a "friend". A civ should consider the negative impacts from becoming vassals to your friends enemies.
"I will not become a vassal to my friends worst enemies"
Is there any other way of befriending a civ than having >10+ diplo relations with them? I don't see how some civ that has a -10 diplo relation to me would ever consider me as their friend unless i lick their a** until they get a +diplo relations with me.
Find other friends... Right, so they can vassal to my enemies too after having spent thousands in coin and fed them with resources for ages.
And it's only natural that if the game's settings do not reflect your vision of the game that you should turn it off. But that doesn't make it necessarily broken because it doesn't suit your needs.
Yes, the reason it is broken is because it is a locked situation. First off there should be a big bold red warning text stating "This deal cannot be canceled!" and then a link to a civpedia article that explains what it is. (Because it's an abnormal game design, all other deals can be canceled in X number of turns)
Further more, a piece of paper or handshake has never stopped a civilization from breaking said agreement. The only thing keeping the world in relative peace is the fear of repercussions from other civs against their actions.
There are plenty of nations that would love to murder each other. Neither are in defensive pacts but if they start something then the world will think of them as the villains and bombs will start flying. (Libya?)
My initial point was that your annoyance was spurred from taking a vassal without understanding the very ground level basics of the vassal system (IE that it cannot be canceled by the player). Why not take peace? Or even a Cease Fire since a 1 city civ generally doesn't have anything to offer in

and will never give up any techs they have over you. Just cease fire or take whatever you can from peace. Then, send a small contingent towards his last city and finish him off once and for all. Or don't. If the AI takes a 1 city civ as a vassal during peacetime, it's his own mistake.
No matter how had i think about it, i have never seen any other deal which simply cannot be canceled. I went on the assumption that i could cancel the deal later on. (much later on in fact)
I also never knew that i could demand offerings from a vassal until i realized i couldn't break the capitulation agreement. (EVER)
Where all other deals can be canceled at one time or another, the vassal system sticks out like a sore thumb. It just doesn't fit with all other game mechanics, it's broken!
You can utilize vassals in any type of victory condition. Often, they can be used as a buffer between yourself and another civ that could be a bit more aggressive. Your particular gripe is about vassals with respect to war, so saying not all players play only for conquest is kinda moot.
This is a domination game but the AI plays it as if it was conquest. They declare wars left and right even though they still have plenty of land to grab.
There's at least 20 tiles between each civ except for the 2 civs that are close to me that i have befriended.
The reason i wanted to keep them around was a role playing aspect, they are civilizations i like IRL.
I could just as well not have bothered with them and let them fall to ruin.
And i never employ the slavery civic for the simple reason, i don't like slavery IRL. Even though slavery is a powerful civic to have!
Where most other game mechanics in Civ 4 let you shape your experience to some extent. The vassal system invalidates all efforts you make with diplomacy by merging nations that hate each other indiscriminately.
Add to that, i can never become a vassal to an AI player... I have to fight or die.
As previously stated, Defensive Pacts are better suited to your ideas regarding protection of weaker civs. They will often come to you with such requests (particularly when you are much more powerful than they are). Turn off the vassals is a simple solution for you. Or, you can always learn the ins and outs of said systems and use them to your advantage.
The ins and outs of the system as far as i can tell is that it is broken. Why should i be interested in a mechanic i deem to be broken?