In The Taliban Strikes Back, Gary Brecher (The War Nerd) describes how insurgency works:
So overall, Afghanistan has rotten living conditions — not a promising market if you’re selling the new iPhone, but perfect conditions, lab-level perfect, for selling rebellion. In the early stages, successful rural insurgencies don’t even worry about combat much. They focus on quietly setting up a local government that replaces the occupiers’ puppet government. If you’ve read much about how the Viet Cong worked in South Vietnam, you’ll recognize the pattern: The puppet government runs around looking busy in the daytime, but when the sun goes down the guerrillas go into action, collecting taxes and settling local disputes, even holding court proceedings in caves, barns or somebody’s hut. The idea is to keep the locals from contacting the occupiers, denying them basic intelligence about what’s going on in the villages, and at the same time making your group indispensable by helping to handle the local feuds, even helping them in the fields. The Taliban has spent the last six years doing all that, to the point that most of Afghanistan now has Sharia-based Taliban courts settling criminal cases.
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To make up for the big gaping hole where our military intelligence should be, we’ve been using William Westmoreland’s failed formula: massive firepower. Donald Rumsfeld’s doctrine of doing counterinsurgency warfare on the cheap, with very few troops and lots of air strikes, means that the ISAF has very little local intelligence and has to depend on air power, which worked well enough in the initial defeat of the Taliban in 2002, but just plain doesn’t work in counterinsurgency warfare, because that kind of warfare is about not firing until you know exactly who you’re shooting at. To gain that sort of local knowledge, you need troops settling in to the villages, getting to know people. What you don’t need is F-18s orbiting at medium altitude looking for targets. Unfortunately, that’s what we’ve been using to suppress the Taliban.Those fighter jets can’t tell the difference between a wedding party carrying the bride to her husband’s village and a Taliban column moving to the attack. And when in doubt, they tend to assume all large groups on the move are Taliban. For six years, ISAF warplanes have been bombing Pashtun wedding parties and processions. It seems to happen over and over again. I’m not sure why. Maybe weddings are the only time that Pashtuns get together in big numbers, big enough to draw fighter pilots’ attention. Maybe it’s their habit of firing rifles to celebrate. But for whatever reason, we have bombed and strafed enough wedding parties to rouse centuries of hatred from the Pashtuns.