AIs allying with enemies against the civ in the lead?

[Shadowlord]

If a single player is more powerful than anyone else (and is warmongering, at least), how often will the AIs ally with other civs (including ones that they normally aren't on the best of terms with) against the sole superpower?

I'm wondering if they are willing to temporarily ally with their enemies in order to deal with larger threats?

For example, the USA and USSR allying against Germany in WWII. Or, as a peacetime example, the system of alliances in Europe in the 1800s and early 1900s, which were (IIRC) intended to serve as a deterrant against war. Of course we all know how that turned out...

(I'd liken the alliances system prior to WWI to putting a box full of nitroglycerin in the middle of a town with a note on it reading "DO NOT OPEN, BUMP, OR OTHERWISE DISTURB - WILL BLOW UP IN YOUR FACE!" You just know sooner or later some crazy Kaiser Wilhelm is going to come along and try to bust open the box with a crowbar for [Censored!]s and giggles, heedless to any risk to himself or the rest of the town.)

[Solver]

As far as I observed, the AIs make no such alliances to stop a big threat. Not really. You can conquer one AI while trading with the others, then take out the next one and carry on like that.

They do make alliances, but they are based on them, say, being good like the Torians and Altarians. But seemingly no such thing as NATO-style alliances to counter a threat.

[Gufnork]

They do have a parameter that makes them work against a threat, but it's not very good. I've had a few calls from other civs claiming that this or that civ is a threat and that we should work against them. The civ they're talking about is never a threat though, so I have no idea why.

[Peets]

I have noticed that some will support those who are in war with a big threat. Providing ships, money etc. But that's it.

[Hansolo88]

It's definitely written into the game, though how well it works is a different matter entirely. Probably something that Brad and/or modders will continue to tweak and balance, it doesn't sound hard to edit.