Sometimes I wish that every time someone with a Ph.D. or a Star said the word "Ideology" that a stun gun would go off in their shorts. A kind of IAIED (ignorance activated improvised electrical devise).
Why has the insurgency in Afghanistan lasted so long...why do insurgents fight. Because they have all been indoctrinated at "Taliban University"? We need to give these people some credit. They are no more brainwashed auto matrons than we are.
At the lower level, the rank and file, they appear to me based on what I see here today, the people I talk to, and what I have read about the past couple of thousand years of history of these people in this land is that they fight because they belong here and we don't, and we are here, and they also get paid an honest wage to fight us. This is not rocket science. (Ok, everyone out there who just thought "oh yeah, what about the Islamism ideology", please imagine a stun gun going off in your shorts.)
At the higher end, there are those who are on the "ins" in this country, and those who are on the "outs." If you are in the “ins”, you get to place people in the high positions that control influence, power and money. If you are on the” outs”, you get the scraps. Your family gets the scraps; your tribe gets the scraps. So there will always be those on the “outs” who are looking for their opportunity to get on the “ins”. This may happen when an invading Army rolls into town, and you hitch yourself to that army. It has happened over and over again. Or, if you were on the “ins”, and were put on the “outs” by the invading army you look for cracks to chip away at. A great crack to chip away at is if the new government does not possess a legitimacy recognized by the portion of the populace on the outs. Now, they all want on the “ins”, so you don't have to sell this too hard. Besides, there is an invader in your country and he doesn't belong here and you do.
So, what do you do about this?
First, recognize that there are those on the “ins” and those on the “outs” and they are all looking to either cling to being on the “ins” team, or are looking to get off of the “outs” team. And they will tell you whatever you want to hear to make that happen.
Second, look for chinks and fix them. First and foremost is the legitimacy of the “ins” government. Just because it is 'official' is not good enough. Just because you held elections is not good enough. You have to honestly ask " is it legitimate on terms that mean something to THIS populace?" (Hint, the current government is not perceived as legitimate by anyone, yet alone the "outs" team). Find what means something to this populace and employ it. It may mean that the teams adjust. That's ok, they adjust all the time. Just swallow your pride and work with whoever the new, legitimate "ins" team is.
Third. Reduce your presence. Don't surge, don’t retreat, just go home. Not everyone, but enough so that it is clear that you are not here to occupy or manipulate the place.
Three steps to address "why they fight."
Ideology is like COG theory. Its great fun to think and argue about, but in the end it isn't so important what it is, just that you have thought about it and have one that works.
(Note: No Ph.D.s or Flag officers were harmed in the writing of this post.)