IN THE PAST few years, with the US military battling vicious insurgencies, first in Iraq and now in Afghanistan, there has been plenty of talk about the nettlesome nature of the challenges it faces: "irregular warfare" and "asymmetric threats" are the catch phrases of the day. A military long oriented toward stopping Soviet tanks on the plains of northern Germany and facing down potential adversaries with the promise of nuclear annihilation has had to retool, both physically and mentally, to combat opponents that are as elusive and tenacious as they are low tech and loosely organized.

The Army has transformed its counterinsurgency strategy, moving away from a reliance on "shock and awe" to a suppler set of tactics that play off of local culture, political fissures, and the...