I read over the Just War Doctrine as detailed in the link. I note the absence of what I consider an important precondition to the whole consideration of war and/or of 'just war' that is rarely if ever presented for any fair and reasonable public discussion.
Namely, "Does the aggressor have a legitimate grievance?" Secondarily, "Despite the legitimacy or illegitimacy of the grievance has there been a thorough consideration of the relative costs of going to war vs. the costs of addressing the grievance?" Thirdly, "Have any efforts been made to address the grievance in whole or in part?" Considering how little attention these considerations typically receive (generally none), I find it hard to consider any of the known war doctrines legitimate.
In regards to the doctrine in the link, I can only ask, "At what point and under what conditions will we have these supposed statesmen who act in the interests of the common good?" I've yet to hear word of such a state of affairs visibly persisting anywhere in the world at any point now or in our collective memory (aka the historical record - the Buddha's references to wheel turning monarchs in the ancient past [frequently dismissed as mythical - not by me], as the recollections of one historical person, are both accepted and excepted).
It seems to me that most of the overt and widely destructive warfare in the last century has arisen from the global promotion of the pernicious concept of the right to assert a national identity, frequently in conjunction with territorial rights, (thanks again America!). Given the present context where a global non-culture is impacting, compromising and homogenizing all cultures and will likely overcome all cultures it might be best to give serious thought to discern that which is valuable and retainable from any and all of the traditional cultures we have variously known and do all that we can to preserve what we can. Retaining the way of life of traditional cultures can more or less be considered a lost cause. If we likewise see a disappearance of "national identities" it need not be considered a complete loss if we can each retain and maintain that which is of real value to us as individuals and as a species. If we cannot face up to the emerging conditions and set aside our former identifications we will of course suffer far more in the future because we are not facing the arising of a monoculture or of a dominant culture but the end of culture more or less entirely as we have all variously known it in the past.
In the context of this emerging non-culture there is a decreasing 'tribal' basis for warfare and so fewer outlets for the warfare goods and services franchises. As they say in the industry, "It is not the one gun for every twelve people on planet earth which is the problem, the question is, "how do we arm the other eleven?" In a studious effort to prepare for this we have already seen the beginning of "conceptual wars" such as the "war on drugs" and the "war on terror" and by casting persisting and visible social differences in this light a context for "perpetual escalation" is guaranteed thus guaranteeing the future growth of the War Industry, which has already long been the dominant economic sector. Social stability and the maintenance of the ongoing hierarchical social structure will probably also increasingly require more overt forms of "class warfare" than those which predominate today.
My personal answer after long consideration and reflection is "No". No to war. Period. No to violence. Period. None of it is ultimately justifiable when one is as fully aware as is possible regarding the overall context of one's existence (and it was my working assumption that until such time I had no thoroughly considered justification for offensive or defensive violence and so my position has remained consistent). Naturally most will object to such a blanket statement on any number of grounds, which if we explore that ground, eventually are found to be groundless. A common example is offered by those who will "do anything to defend their children". I understand. My choice, suitable to maintaining my stance, have no children, therefore no children to defend. And so on, no to self-defense, etc, etc..
But whoever walking, standing, sitting, or lying down overcomes thought, delighting in the stilling of thought: he's capable, a monk like this, of touching superlative self-awakening. § 110. {Iti 4.11; Iti 115}