Once upon a time, there was a civilization that had a prophecy that it would continue to grow and prosper so long as it kept conquering its neighbors. There was a catch, the civilization could never lose a battle or the civilization would fall.

The civilization conquered, grew, and prospered until it lost a battle and then it simply collapsed. It's as if the citizens lost all hope in the face of their own fulfilled prophecy.

What civilization am I thinking of?

I've been trying to relearn the name of this civilization for years. Thanks.