"I am God's Punishment for your Sins"

The Loneley Planet of Cantral Asia (with contributions of Mongolia LP writer Michael Kohn) mentions Chinggis Khaan (or Jenghiz, as they have transcribed it) and his army invading the city of Bukhara.

It was this brilliant city, as soldiers raped and looted and horses trampled Islamic Holy books in the streets, that the unschooled Jenghiz assended to the pulpit in the chief Mosque and preached to the congregation. His message:"I am God's punishment for your sins"

LP continues to conlude that this 'shocking psychological warfare is perhaps unrivaled in history'

For more details, and some doubt, on this see John Man's Genghis Khan.