The inability of the United States government to anticipate the ISIS offensive that has succeeded in taking control of a large part of Iraq is already being referred to as an "intelligence failure." To be sure, Washington has unparalleled technical capabilities to track money movements and to obtain information from the airwaves. It is adept at employing surveillance drones and other highly classified intrusive electronic methods, but there is an inherent problem with that kind of information collection: knowing how the process works in even the most general way can make it relatively easy to counter by an opponent who can go low tech.

Terrorists now know that using cell phones is dangerous, that transferring money using commercial accounts can be detected, that moving around when a drone is overhead can be fatal, and that communicating by computer is likely to be intercepted and exposed even when encrypted.