Insight Into Tribes
Please read this .pdf file written by US Major Jim Gant, an Army SF operative, on the tribes of Afghanistan.
For my two cents, I am nowhere near as interested in the scrap over in AfPak as I am in the coming brouhaha on these shores.
But I am very interested in what has made tribal arrangements over there tough enough to survive whatever empires over the past 2300 years have been able to project against them.
Some of the answers to that question are contained in the essay, along with a related series of videos here:
It's The Tribes, Stupid
The Citizen vs. The Tribesman
Tribes Are Different From You and Me
Fighting A Tribal Enemy
How To Win In Afghanistan