How do I resolve an Alliance War?

[Fried Noodles]

Short of 100% eliminating all hostile factions, that is!

I am playing as Liu Chong in the Mandate of Heaven start. After stabilizing my economy after the rebellion ended, I've started focusing on boosting my own economy and trying to strengthen myself diplomatically by putting together a large network of factions through a coalition and vassals.

I've been fairly successful creating vassals and they haven't really caused me too much trouble until a little while back.

One of my vassals came under attack from Ma Teng and they requested my aid. I had a quick look -- Ma Teng is way on the west side, out of my hair. "Sure," I thought, "I'll declare to the rest of China that I'm helping you!"

I didn't pay close enough attention to who the aggressor was. Not just Ma Teng, but the Alliance of Ma Teng. Ma Teng, Yuan Shao, Yuan Yi (a minor faction that's growing pretty decently).

I'm not really having much trouble with them... I've beaten back a few stacks as they encroached on my territory... But constantly being at war with them is sort of restricting my plans. I have to maintain my armies and keep an eye on my borders.

And there's no option for me to try to make peace with any of the members of the aggressive alliance in the diplomacy window.

All three of them are now flagged as 'Negligible / Negligible' (Their strength / Their allied strength)... But they still seem pretty interested in maintaining the war.

Am I supposed to be able to do something about this? Or am I stuck until I eliminate them?

[Fried Noodles]

So I am in a coalition with Lu Zhi, Cao Cao, Liu Biao, and Sun Ce...

And I have four vassals: Liu Bei, Dong He, Xin Yuejie (not sure who this was originally!), and Shi Xie.

No one else in my coalition is in an alliance war with the enemy alliance. And the only one of my vassals who are currently in this same alliance war is Shi Xie (the one who asked me for help when Ma Teng declared an alliance war).

Talking to anyone in my coalition doesn't give me an option to make peace. Talking to Shi Xie has no such option.

And now (after several battles where I ransom their troops and release their generals), though both Ma Teng and Yuan Shao are trending to positive attitudes (Yuan Shao very loudly says "A JOY TO SEE YOU!" when I talk to him in the diplomacy window), my only diplomatic option for any of the three enemy alliance members is to call my vassals to arms against them.

Edit:
I'm kinda holding off on building up more prestige in my campaign because of this unfortunate alliance war. I very much doubt that Ma Teng or Yuan Shao will be one of the Three Kingdoms in the endgame. It'd be quite hectic trying to fight off armies from that many different factions all at once.

[RCMidas]

Kill off Yuan Yi. Send everything you have at him and wipe him out utterly. That ought to do it. The other two will be happy enough to make peace then.

[Fried Noodles]

I'm not sure why it happened... But I was continuing my war against Yuan Shao and Ma Teng (trying to remove/collect their satellite territory that was very close to my own borders). And I miscalculated how much Prestige I'd gain from capturing the Chang'an Jade Mine.... Been trying to keep my Prestige below 500 before I settled this war. But I hit 500 and triggered the endgame.

Actually worked out pretty well for me. The only other faction in my current game that's militarily equivalent to me, who I was worried might turn against me in the endgame, is Liu Bei. But he didn't declare himself Emperor, and is content to stay my vassal.

My coalition-mates Sun Ce and Cao Cao (both conveniently down south of me) are my contenders for the throne. Sun Ce dropped out of the coalition and Cao Cao left while taking Liu Biao and Lu Zhi with him.

Left me with no coalition whatsoever.

Now that I am alone, and not the sole member of a coalition that's involved in an alliance war with an enemy alliance, I was able to propose peace with Yuan Shao's military alliance.

Weirdness.

[The Standing Tortoise]

Fight it like a World War. You are Poland. Do what you think is necessary until the enemy is pacified.