. >> lehrer: those concerns were borne out recently in reporting by james foley of "global post." he talked to soldiers in the volatile kunar province hard by the pakistani border. >> we're infantry guys and we're trained to count our victories with the number of bodies that we clean up afterwards. it's kind of a vulgar way to put it, but it's the truth of it. and we're kind of out of our element. >> lehrer: the core of these fighting units are the sergeants who run their squads and who routinely update their soldiers on the rules of engagement. >> feel like you life is in danger or the life of your buddies is in danger-- engage. you know what i'm saying? you got to use your escalation of force. >> lehrer: the nature of counterinsurgency, called "coin" in shorthand, is trying to separate the enemy from the people. and it is inherently difficult, complex and not a little frustrating to the troops carrying it out. >> when you destroy fighters, it makes you feel like you've accomplished something. it's very hard to feel like you've accomplished something in a coin fight because it ta