A Soldier who fights in a high-intensity war against a uniformed enemy can confidently assume that every enemy soldier is a combatant, a threat, someone whom it's morally permissible to kill. That's why Soldiers don't fire warning shots; instead, they aim to "put two in the chest." People downrange are to be killed unless they surrender or become incapcitated.
In contrast, a Soldier who is part of a security force in a situation where his mission is to protect the people and where a non-uniformed enemy hides among the people, such as the situation we face in the Iraq COIN, faces a calculus more like that of a police officer. He must assume that people are innocent civilians until evidence suggests otherwise. People downrange are to be protected unless they show hostile intent.
This puts Soldiers in a bind; it gives the bad guys a huge advantage. The bad guys usually get to initiate fires, forcing Soldiers to transform from cops to killers in an instant.
I worry that this too easily creates an over-reaction. Our Soldiers are doing a remarkable job overall of limiting collateral damage, but one area I worry about is some units' "react-to-contact drills" that include firing every weapons system, immediately in all directions, as suppressive fire, with or without targets. Doing this, of course, often leads to harm to innocents, which can be traumatic to the Soldiers who did the firing. Needless to say, it also furthers the insurgents' cause, "proving" that we don't care about the lives of Iraqis.
Like I said, this is a huge challenge for leaders on the ground. With very few exceptions, we ARE adhering to the laws of war, while the insurgents and terrorists are violating just about EVERY law of war (e.g., steal an ambulance, execute the driver, pack the ambulance with explosives, and intentionally kill children; does it get any worse than that?), to include not wearing uniforms.
But we have to find and share effective ways to help Soldiers transition seamlessly and continuously between their roles as warfighters and security forces. Soldiers who kill innocent people because of TTPs that privilege "force protection" over "moral justification" will one day pay the price of PTSD. Leaders need to be proactive and continuously seek ways to train their Soldiers to make justifiable moral calculations, even in the most difficult circumstances.
note: Thanks to LTC Tony Pfaff, whose ideas in this area have sparked my thinking. He has written a chapter (one I've heard about but not read) on this topic in a forthcoming book on the Army Profession.