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...).