Can someone, anyone, offer an example of a civilization that welcomed its enemy into its own tent? Has there ever been such self-immolation? Ever?
Trojan horse!
The Greeks.
The Persians.
The Aztecs.
The Inca.
And that is just to start.
Once you get comfortable and think that nothing can touch you, that is when you let the enemy in. They are generally let in to help you make advances against your rivals. And then you find them at your own throat.
You die crying, "I didn't mean for this to happen!"