'A War' is an Oscar-nominated Danish film that deals with what happens in the field and on the homefront when warfighters are made to fight with restrictive rules of engagement. As much as the film is a story about one officer's experience (and how his choices under fire potentially affect his family) it is also a commentary on the nature of the limited wars that members of NATO and ISAF have found themselves involved in since 2001.
The war in Afghanistan has been specifically challenging with respect to ROE. The enemy isn't another nation-state. Some areas are more secure than others, but overall there are no front lines. Add to that the overall mission of convincing the local populace that modernity and following a western model of rule of law is the better choice over the savage and unmerciful nature of Sharia law and the draconian elements that come with it. The ability to win "hearts and minds" is heavily leveraged against avoiding collateral damage while attacking the enemy.
All of that distills down into an ROE matrix that requires the warfighter in the field to accept risk. This primary mission is keep the locals safe; it's not keep your troops safe. And it's not kill the enemy at all costs.
In all-out warfare unflinching ROE can be established, stuff like "if it flies it dies" and "everything east of this longitude is hostile." In limited war the steps are complex and nuanced, almost like trying to build a case in a courtroom. Only a battlefield is no courtroom.
In limited war the fact your unit is under attack doesn't give you carte blanche to defend yourself. "Positive ID" must be established. You have to be able to prove you know where the bullets are coming from before returning fire rather than destroying whole city blocks. You have to be able to tell "the pepper from the fly shit," as they say.
Complying with this PID methodology gets harder when troops start dying around you. At that point you're apt to do whatever it takes to make it stop.
And once the shooting does stop and you're back in the antiseptic light of day, you will be judged on your conduct. You'll be judged by those who weren't there, and who probably never have been or ever will be there.
Such is the essence of the Post-9/11 conflicts. The harm into which we've sent our most recent generation of warriors is distinct from those who fought before them, and the respect they're due is unique and equal.