Kinda reminds me how the Greek Leagues kept allying with the Romans in order to defeat the Macedon kingdoms, which caused Rome to estabilish larger and larger presence in Greece, while the Greek leagues and kingdoms weakened, until they inevitably annexed them.

Come to think about it, the Aztecs themselves were partly defeated because they were so hated, every other tribe in the vicinity helped the Conquistadors, which ultimately was catastrophic for everyone but Spain.

Better the monster you know...