If a State A attacks another State B's military apparatus knowing full well that there will be civilian collateral damage, then why is it that even if State B retaliates by intentionally targeting civilians, it's terrorism?

State A may know that there may be harm caused to civilians, as a matter of probability, but without targeting civilians, for example during the invasion of Normandy. If State B targets civilians and does so with the intention of causing terror, that is a very different matter, for example in the Blitz and the bombing of Dresden. At least so says the just war theory. And there is sense to it. A defensive war could not be fought if one expected no unexpected harm to innocents. But intentionally and deliberately harming civilians or non-combatants is an element in terrorism and more broadly in military actions that are not just. All this (and more) is the point of the law of double effect, which is an extension of Aquinas' treatment of homicidal self-defense. In defence of myself, do I intend to kill my assailant? Or does that killing come about as a foreseeable but unintended consequence of my self-defense? Besides, Aquinas' example was concerned only with self-defense, and there is no imaginable...

Andrew is obviously right, but what he is proposing is actually a utilitarian basis for double effect.

Many Americans maintain that, while they oppose the Iraq War, they nonetheless "support" the troops wholeheartedly. But is this distinction a mere fantasy? The US has an entirely volunteer army, so why isn't a citizen who joins the military just as guilty for atrocities committed abroad as army or government officials?

Is it possible to oppose the War and yet supportthe troops?If I support the war, that means I believe the ends are justified andgood, themeans are appropriate, and so on. So I believe in the mission, as youmight say. Whatdoes it mean to "support the troops"? It might mean that I writecomforting "lettersfrom home" to people in the services, that I have positive feelingstowards thesoldiers, that I applaud their representatives on the 4th of July, andso on and on. Thesetwo activities are very clearly different and perfectly distinct, asthe support has two different objects, and there is plainly no fantasyhere. The more seriousquestion is whether it is morally permissible to engagein the second activity (supporting the troops) without the first(support for the war), or if we think the war is positively wrong. To put anextreme case: could (a moral "could" here) goodGermanshave supported the Wehrmacht, the regular army, even though they didnotsupport Hitler and the War and its stated aims? And would it...