In Knowing the Enemy, George Packer cites David Kilcullen on global counterinsurgency:
One good example of Taliban information strategy is their use of “night letters.” They have been pushing local farmers in several provinces (Helmand, Uruzgan, Kandahar) to grow poppy instead of regular crops, and using night-time threats and intimidation to punish those who don’t and convince others to convert to poppy. This is not because they need more opium — God knows they already have enough — but because they’re trying to detach the local people from the legal economy and the legally approved governance system of the provinces and districts, to weaken the hold of central and provincial government. Get the people doing something illegal, and they’re less likely to feel able to support the government, and more willing to do other illegal things (e.g. join the insurgency) — this is a classic old Bolshevik tactic from the early cold war, by the way. They are specifically trying to send the message: “The government can neither help you nor hurt us. We can hurt you, or protect you — the choice is yours.” They also use object lessons, making an example of people who don’t cooperate—for example, dozens of provincial-level officials have been assassinated this year, again as an “armed propaganda” tool — not because they want one official less but because they want to send the message “We can reach out and touch you if you cross us.” Classic armed information operation.
(Hat tip to Erik.)