Many of you know Steven Pressfield from reading his book Gates of Fire - a riveting account of the battle between the Persians and the Spartans at the "hot gates" of Thermopylae. As an aside, that novel is required reading at Westpoint. According to Wikipedia, the book has achieved "cult status" among US Marines.
Steven Pressfield is a student of history - and an astute student indeed. His bibliography is impressive. In addition to Gates of Fire, he's written Tides of War (Peloponnesian War), Virtues of War (Alexander's campaigns), Last of the Amazons (Theseus and his band of female warriors), The Afghan Campaign (the son of Alexander and his campaign in Afghanistan), and Killing Rommel (WW2 and the Long Range Desert Group).
If you want to get inside the mind of the warrior culture, this is your author. He's got 5 web-episodes (5 minutes each) at his website - Steven Pressfield. In them he delves into the military aspects of tribes, and compares Western Citizen versus The Tribesman.
Here's episode 1 - "It's the Tribes, stupid"
The interesting parallels that he makes is that the Tribal mindset what gives the Tribe its power. You can think of Tribes not just relating to American Indians or jihadists, but also US Marines and Gang members. It all makes sense. He points out the folly of entering a region of tribesmen with the intent at "establishing democracy" because the tribes don't really have the same values as we do.
The most poignant commentary is how we are doing the same thing right now in Afghanistan that Alexander did back in 300BC. The arc is almost exactly the same.
Check it out.