In my current game, Frederick was attacked by Hannibal who eventually took one of the German cities. However they made peace not long after that. In a few turns, Frederick, who was Pleased with me, came and suggested that Germany becomes my vassal.

Here goes the question: what are the pros and cons? I understand that it might be quite "convenient" to get a vassal in a war: you don't need to spill more blood while you still get some outcome of your success. However, a "peaceful" vassal can simply quit from under your control after 10 turns and that's all.

In this particular case I accepted the proposal, as I was planning to attack Hannibal anyway. However I would appreciate others' opinions on this matter. Why would one need a "peaceful" vassal?

Half of the vassal's land area counts toward your domination victory.
Vassals always vote for you in diplomatic matters, which helps toward diplomatic victory.

Cons... the implementation of vassalge is a little flaky. For example, Brennus asks to become my vassal. I accept and immediately get a message that I have declared war on Russia. Brennus had been at peace with Russia the turn before and he shouldn't have been able to declare war as a vassal. Did he declare war and I just wasn't informed about it? Perhaps.... so I reloaded. When Brennus asks to be my vassal, I turn him down. When my turn comes up, I check diplomatic relations and Brennus and Stalin are at peace! Something is fishy with the way vassalage was coded.

Yes, the vassalage system is not yet perfect now. For two things: when a civ attacks a vassal state it doesn't regard the question whether it wants to be at war with the master. And second: when a civ makes a request (that arrives in your turn) it may be obsolete because of some other event that happened in the same turn.

Both things are said to be solved in the long awaited patch.

For now I don't accept any vassalage request.

Half of the vassal's land area counts toward your domination victory. Vassals always vote for you in diplomatic matters, which helps toward diplomatic victory.

Yes, I know that. However I am far away from the domination victory yet. Neither the diplomatic victory is possible, as I usually disable it.

Cons... the implementation of vassalge is a little flaky. For example, Brennus asks to become my vassal. I accept and immediately get a message that I have declared war on Russia. Brennus had been at peace with Russia the turn before and he shouldn't have been able to declare war as a vassal. Did he declare war and I just wasn't informed about it? Perhaps.... so I reloaded. When Brennus asks to be my vassal, I turn him down. When my turn comes up, I check diplomatic relations and Brennus and Stalin are at peace! Something is fishy with the way vassalage was coded.

I see. Fortunately, nothing really bad happened to me after I accepted Frederick to become my vassal. Nothing really good happened either though.

Thanks for your comments.

...Cons... the implementation of vassalge is a little flaky. For example, Brennus asks to become my vassal. I accept and immediately get a message that I have declared war on Russia. Brennus had been at peace with Russia the turn before and he shouldn't have been able to declare war as a vassal. Did he declare war and I just wasn't informed about it? Perhaps.... so I reloaded. When Brennus asks to be my vassal, I turn him down. When my turn comes up, I check diplomatic relations and Brennus and Stalin are at peace! Something is fishy with the way vassalage was coded.
I agree that this sounds fishy, but I wouldn't put it to the coding. It seems like a glitch. I imagine you reloaded and accepted him as a vassal again to see if it happened a second time. I gotta say that I've accepted many a vassal and I've never had an unexpected declaration of war. I rather like the vassal system, but agree that it needs to be tweaked.

The diplomatic consequences can be huge. In a game a couple of weeks ago I accepted Alexander as my Vassal. I soon realized that everybody, and I mean everybody, disliked him. The consequence was that all my former friends now started to dislike me. :( Therefore, my advice is to carefully check the leaders status because Vassalage can easily ruin years of diplomatic efforts.

I too have learned the lesson above. My new rule of thumb is to ask why does this guy want to be my vassal? If he's just a victum and getting beat by a guy who doesn't like you anyway then it may be worth accepting just to get the good excuse to go skullthumping. If he's a dang jerk and has honked off everybody then throw him under the bus and declare war on him with everyone else so you can try to get the mutual armed struggle diplo bonus rather than the vassalized rivals penalty.

~C

I useally dont do it do to the cost for vassal state

You forgot a Pro. You can direct the research direction of your vassal and-if it was a 'peaceful' vassalage, then its pretty long-odds that he will give you the fruits of his labour at 'mates rates' ;). Oh, and if you don't abuse them too much, a peaceful vassal will stay with you a VERY long time!
Oh, and in MP games, Vassalage ROCKS, no matter what end of it you are on ;).

Aussie_Lurker.

Oh, and in MP games, Vassalage ROCKS, no matter what end of it you are on ;).

Aussie_Lurker.

How so?

I only needed 10 but here's a few more.

Oh, its a fairly long story, but the short version is that in our most recent game, one of the more powerful players in the game decided to come after me (true, I provoked him by taking one of his border cities but-hey-he ought to have defended it better ;) ). Anyways, backed into a corner, both myself and another tadpole ;) went to this guy Frank and begged him to Vassalise us, which he did. This has now put him in a state of war with our enemy, which takes the pressure off us, whilst at the same time allowing us to force this other guy to split his forces. Good for ALL sides.

Aussie_Lurker.

Cool, I wasn't sure if you could vassal online. This isn't a mod right? Do the same penatlies apply to the human as it does to the AI in the game? Or do the vassalage penalties fluxuate with the game difficulty?

No mod, just a regular Multiplayer game. Not sure about the penalties, as I am the slave-not the master ;) :p.
Either way, with his 60gpt, I get the feeling he could afford to take us two tadpoles on board!

Aussie_Lurker.