What to do when two competing civs grow too much and ally together?
i recently played a game where two civs (Montezuma and Augustus i think) expanded so much that they were so far ahead of the rest of us that it became apparent we will lose. When i first noticed this i started to look for allies against them, forming pacts of secrecy etc. However this didn't help at all and when i tried to ally with one of them against the other i learned they are actually already allies. In a few turns i had their armies at my borders and it was pretty much game over. This was on Warrior difficulty, if it matters.
My question is: how can this be stopped? There were a few other civs who tried to get me into a war with one (or the other) of them early on in the game, but at that time it was not apparent they are so strong and i didn't want to get into a conflict early since i was aiming for a cultural victory. Was this the mistake?
Note: looking for an ally was probably impossible. The Chinese were very weak (useless), Americans got wiped out by Augustus very early and the last guy was a pacifist (i cant remember the name of the civ, but probably the leader was Ghandi? That old man...).
Sounds like you were unfortunate to not spot the issue earlier; probably the best thing you could have done at that stage would be to fortify your borders, hope to deflect the first wave (when it eventually comes) and then counterattack, charge in and capture and hold a few of their cities (thus making them weaker). Although if you were aiming for a cultural victory you would need to avoid annexing any, otherwise this will make your social policies cost more.
In my experience Montezuma and Augustus are, by default, quite aggressive when played by the AI; if you find an AI playing either near to you, I feel it is best to plan ahead to stop them expanding too much and have sufficient defence on that border - or instead try to make sure you get friendly with them so they're on your side instead.
Also, I believe entering in to a pact of Secrecy with other Civ's against a threatening Civ earlier in the game would have helped prevent the other Civ's becoming allies with the threat later on, by ensuring they have a "bad" relationship with the threat. But I don't have hard evidence for this.