This report by the Combating Terrorism Center at West Point is simply outstanding:
From the report:
The key insight is that terrorist groups, and other covert organizations, face two fundamental trade-offs. The first is between operational security and financial efficiency. Here problems of trust and controlâ€”agency problemsâ€”create inefficiencies in resource allocation. Strategies to mitigate these problems all entail security costs. The second tradeoff is between operational security and tactical control. Here agency problems and other group dynamics lead to counterproductive violence. Strategies to mitigate these problems through greater control entail security costs for groups as a whole.
The report relies on previously-classified documents from the DOD’s Harmony database for the case study that supports these ideas. It’s definitely worth a read.