I can understand the temptation to over simplify these issues. However, this is not a case that is simple. While you are correct that the amount of time that the act is meditated upon is of generally no consequence it does factor into the morality of the issue. Pre-meditation does not necessarily mean that the act of conceived years, weeks, days, hours ago. Rather it means that the person had enough time to fully reflect on the act. Remember sufficient reflection is a necessary factor for a thing to be a Mortal Sin. But we also have to define terms.
There is a reason why in both scripture and in the study of morals that we make true distinctions between murder, homicide, manslaughter, etc. While all of them involve killing another person they are not all equal “ways” of killing a person. There is a world of difference between killing a person in malice and killing a person in defense. The end result is the same but the disposition of the actor (the person killing) is very different. In any act from lying to killing all aspects of the act must be looked at and not just the result of the act.
This is a very poor definition as it assumes that soldiers are innocents. This is not correct by the very nature of their function. Once a soldier takes an oath to protect and defend and to fight they are no longer innocents by the very nature of their obligation. This does not mean that a whole-scale slaughter can be justified in a way but rather that in the act of war proportionate means of action can be exercised within the scope of objective morality as treated in the act of war.
Exactly. Even apart from the study of morals Sacred Scripture also makes these distinctions in many and various places. When Scripture is taken as a whole on this topic it speaks of the use of killing, war, murder in various ways. Some are treated as never acceptable but others are treated with dignity. So, for any person to overly simplify the issue is to wear a set of blinders.