The New Counterinsurgency Era: Transforming the U.S. Military for Modern Wars by David Ucko:http://www.amazon.com/gp/product/158901488X?ie=UTF8&tag=abumuqa-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=158901488X With a host of recommendations by the like of Steve Metz and 'Hal' McMaster.
You say the U.S. military is "learning" counterinsurgency. To what degree do you think it has thus far been successful doing so?