There are two kinds of war, which is to say that there are two distinct and separate categories of warfare. One kind that we know is that waged by Nations against other Nations and that is formal, legitimate war or war that takes place within the accountability structure of Nation States. Nations are accountable actors and they are all equal as to type: while some are larger and more capable and others weak and less capable they are all Nation States as a category and represent a place on earth, a people living within that territory and even when inflicted by forms of dictatorship or despotism that government is one that is accountable to its fellow Nation States for its activity amongst them. Accountable military actors represent that Nation, are held in an accountability structure by that government, fight under a banner and wear the uniform of that Nation and are amenable to the formal structure of war which includes cease-fires as a form of treaty (indeed the highest form, even when temporary) and can be officially ended by the governments involved, even to the point of extinguishment of one of those governments to end it.
Formal, declared war is a way for a Nation, large or small, weak or powerful, to assert its standing as a legitimate actor for its people to act with respect to them so as to assert their standing as a Nation amongst all Nations to be treated like any other Nation. It is an understood venue of war that, even in the era of Total War, has limits to it which is the ending of one (or more) of the governments involved as institutions. The people who had been under that form of government now have the right, as a people, to decide their own way in the world and settle internal problems and re-establish legitimate government. Often that has not been the case in the history of mankind and the results can be ethnic populations that undergo unrest, cause civil war and otherwise seek to reassert their people's right to having a definite and defined government that is different than the one imposed on them. When that government is defined, when it raises a banner, when those fighting to establish it put on uniforms and place their military actions as accountable to their rebel government and to the people for which they are fighting, they are performing an act of legitimization in seeking to establish this government to represent these people. This, too, is legitimate and if but one Nation amongst the brotherhood of Nations recognizes and supports them then this organization is considered a Nation coming into being.
In summary that is one category of war and while war is a horror at least this type of war can end and reach a settlement. That is desirable amongst the affairs of men. No matter how many die, no matter the brutal logic that it entails, this formal form of warfare is desired when peace cannot be sustained due to the differences amongst men within the brotherhood of Nations.
There is another form of warfare, however, as war is not born amongst Nations but within the hearts of men as an inalienable right and power that cannot be divorced from individuals. Indeed we recognize that this happens amongst animals who have a right and power to defend themselves against predation, and those seeking such predation we call predators. The actions of such warfare is, then, depredation: that of acting like a predator upon others with no formal recourse against such actions. This form of warfare, by its nature and source, is informal and takes place by men as individuals who can form groups but form no government and seek to establish no Nation. If civilized man recognizes that Nations and the State system used to run a Nation are limits upon passion to which we submit so as to have a protection of our society as distinct from other societies and to be represented, then it is to be recognized that those adhering to this framework agree to quell their passions and allow for only accountable actors to declare war. Those that seek to act with the power of war on their own, no matter their reasons, if they become an unaccountable actor amongst Nations, then we are to call their actions depredation. By renouncing to utilize the civilized form of accountability, they reduce themselves to their savage nature, which is base in all regards, and that they have reduced themselves to savagery as they now put their actions into only one venue of accountability: warfare.
This kind of warfare is of a separate kind and nature from formal war and it is informal and illegitimate war. If the formal kind is that done in public with accountability and, thusly, Public War, then this form done in private with no accountability is Private War. These are distinct and separate categories of warfare and have been recognized as such since the dawn of mankind and the first Nations created by man to represent a people. If a Nation is a creative framework to foster an understandable system amongst men, then those performing Private War are antagonists to this agreement and see that only the natural, savage predation structure is valid and legitimize that viewpoint by their actions. We call these people by various category names, yet they all have the same underlying viewpoint to them: pirates, brigands, corsairs, freebooters, armies of thieves and terrorists. That list is not all inclusive, but demonstrates that the supposed cause to perform such Private War is not limited to any ideology nor religion, but is universal in its scope. Thus no matter what stated cause those performing such actions are claimed, their activity is, one and all, savage and against the structure of Nations in all regards. This is not a 'clash of civilizations' as that puts forth that there is a structured environment for such a clash to take place amongst men to sort out their differences. No this clash is amongst the civilized of all kinds and against those seeking to assert their will upon all mankind no matter if it be to plunder or booty, or just to become a warlord over a people and subjugate them to the will of that savage predation.
Private War can have many stated causes but its effects are the same, universally, and it is to tear at the civilized nature of man who works hard to put his savage nature aside and assert his positive natural rights on behalf of himself to his own betterment and, thereby, to the betterment of all civilized men. Civilization is an agreed set of limits upon the actions of individuals to which we hold each other accountable. Those performing illegitimate and informal war hold themselves and their sole standard as individuals up as supreme amongst men and will inflict it upon any they come across if they so like and have no limits upon their actions. If civilizing oneself is an act of construction, then reverting to savagery can only result in destruction of the works of man both physically and as a mental framework that we agree to abide by. Times can, indeed, change and bring forth great and new excitements and stimulation via the heights that can be achieved amongst the civilized of the earth. Unfortunately the nature of nature does not change and is unchanging, and by being part of that framework and natural in all regards (no matter what we create it is all within this realm of nature) we are under threat of reverting to savagery. While man does have a social instinct, as all animals capable of any thought so acquire, it can be put forth that if a single generation of man were to lose the ability of understanding what the limits of his actions are, then the entire edifice of civilization would collapse into savagery and that civilization would need to start all over again from that most base of states within Nature.
It is desirable, indeed part of the foundation of, formal war that there be an end to it and that a regularized course of affairs resume amongst Nations. Nations and their governments called States are not permanent edifices amongst men, however, and it is sobering to see how often mighty Nations crumble under savagery. Sophisticated systems of trade, discourse and intercourse amongst Nations can fall away as dust under savage man and his actions. Building, construction and creation of artifacts and governments is a long and laborious process and yet, apparently, those that seek to end them can do so in very short order as depredation creates isolation from the very civilized structures created by men and those structures are seen as not safeguarding civilization itself. Such governments can implode by ill moves (no matter how noble in cause) and their own weight causes them to implode, yes. Such structures, even those that are lean and capable, can also implode at the slightest hint that they are no longer capable in safeguarding the very structure that allows them to exist.
From this it can be seen that those waging informal war can wage it not just on individuals, but upon the creations of those people in the form of States to run their Nations. Informal, predatory and illegitimate war can be waged against Nations and by their very informal source there is no easy formal way to go to war against those doing this. Military actions without an obvious object cannot be brought into being and only responses given to attacks as the only and defensive venue against those savages seeking to end a Nation and its State. While war can be declared against those creating a safe haven for such actors, those actors are not attached to those people nor that territory and may basely flee to create a new predatory atmosphere for themselves elsewhere. These ones flee the judgment of war against them and seek to inflict it upon the weak so as to weaken all of mankind and liquidate civilization at that most low of levels. The power of any Nation, no matter how mighty, is brought low by such savages as they, by their chosen path, seek to remain unaccountable to anyone on this earth.
Yet, for that, there is a venue that Nation States can take beyond the formal military means and that is to declare such actors who oppose them from the informal realm as being pirates, savages and an enemy to all mankind. These are then not the Public Enemies of a Nation but its Private Enemies and a Nation State can then exercise specific articles against individuals and organizations that are in the Private realm. Within this realm is the authorization of private individuals of that Nation State to be given papers and limits to their actions to predate upon the predators. These are known as Letters of Marque and Reprisal, as they can be given not just to go after a particular asset of such savages, but to bring a fight to them wherever they are within the limits of warfare done by accountable actors. Thus a Public action may be taken and authorized to put Private individuals into the role of accountable and self-organized military to go after the assets of those who seek and make war from the Private realm upon a Nation and its people. Such counter-predation is under the oldest form of understandable warfare that is part and parcel of the savage realm: an eye for an eye, a tooth for a tooth. A simple dollar for dollar accounting in which every dollar of destructive cost that has been inflicted by an individual or unaccountable organization may be legitimately seized by them to yield up Private returns for those risking their lives to do so. This, too, is limited warfare in that it does have an end once dollar amounts of cost value are reached: the score has been evened and settled with as much damage inflicted as has been given. Amongst even the most savage of animals it is understood that the horn of an antelope may gore a lion, that a puffer fish may injure the mouth that bites it and perhaps even inflict a mortal wound where one is being administered. That is savage justice and yet one that is comprehensible to civilized man as we are all creatures of Nature and see this form of reprisal as legitimate as it is not only codified into civilized law but is based in Natural Law.
What this creates, and civilized man is one that asserts creative nature above base predation, is a two-fold system of justice to hold those waging war against Nations accountable.
The first is the martial realm in which such illegitimate actors can be put to death with only the most basic of trials to see if they are fighting for a government in a declared war while wearing a uniform and being accountable to a Nation State's government. Fight without these things and you are subject to the laws martial and your end is summary execution.
Within the realms martial are also the private takings of goods and artifacts and despoiling the very things utilized by savage man to wage war upon civilized mankind. Here the act is to be authorized to do so and then seek out and predate upon the predators, strike where they are weak and take anything of any value or destroy that which they use, and then yield it up for cash payments usually at auction. Demonstrate that these are the goods of such savages and the payments begin to defray the cost they have inflicted in the private realm and the funds flow in from that private realm via the Nation's authorized and legitimate actors. Once the dollar cost of inflicted damage has been reached, the Letters are then withdrawn and those actors formerly utilized go back to purely private concerns.
Together those are the complete martial or war track of accountability: end actors that you run across militarily or those actively waging war against the Nation, and send private actors out to start putting the pain of attacking the civilized upon the wallets and goods of those doing the attacking. This is rough justice but it is the venue that the savages actively seek, thus a wholly vital realm that they will easily understand in their most base of states.
The other realm is that of public law in which the crimes of piracy are applied to those who are caught when not actively engaged in warfare or just at large in the civil venue. Piracy is a simple charge to prosecute as it has a touchstone of waging war without any legitimacy granted by a Nation State. War waged illegitimately can also fall into this venue, but rarely elicits a civil trial save when there are no authorized military actors to take such people into custody. These savages caught in the civil realm an be put on trial and found guilty of their crimes and the proper punishment performed for their actions.
Unlike other forms of civil prosecution, the crime of piracy being both civil and military allows for trials in both venues to occur, although because of the savage nature of such actors the military is preferred as they are the ones best suited to sort out just what is and is not a legitimate military action. Even those prosecuted by civil means for piracy can undergo a separate trial for military crimes associated with piracy: the civil penalties due to death and destruction of property is a separate realm of jurisdiction from waging war illegitimately and while the action may overlap those two realms they each are separated in the accountability chain for that activity taken. There is no 'double jeopardy' between mere civil crimes and crimes of warfare, and both venues are open to civilized man against those waging war without legitimacy and predating upon civilized man. An act of blowing up a building, say, can be both a civil crime (call it terrorism or simple destruction of private property with intent to kill or injure) and a war crime (that of waging war without legitimate basis). Do note that while civil punishments may vary, the military punishment is without variance and must be so to uphold the formal and legitimate form of warfare: by putting such actors to an end there is a clear and decisive statement of what is and is not acceptable in the realm of war by a civilized military structure.
Upon informal war there is a value judgment but it is not one based upon the supposed causes brought forth by those actors, but a judgment that such form of war is illegitimate no matter what the stated cause is. Thus the judgment upon why people revert to savagery is set aside to deal with the fact that they have decided, on their own, to reduce themselves to the savage state of being and become a predator and wage a war of depredation upon all mankind. That martial realm of judgment is hard, nasty and justified as it is not we, the civilized, forcing men to act like savage predators but they who become predators forcing this realm of decision upon us. Sad that they could not take up the myriad forms of civilized discontent to express themselves and create a better world, but that decision is not forced on them to become uncivilized. No matter the supposed 'justice' of a cause, to take up savage war is to wash away all of those arguments and put the most base fact of savage war taken up by individuals into clear stark light. Woe befall those who seek to muddy this starkness and they do no benefit to mankind and can even be seen as trying to debase man to a lower standard by trying to legitimize savagery. No matter how noble the calling, there is not elevated basis for those that choose savagery willingly and no trusting them in the future to be reformed as they have so easily shrugged off the burdens of being civilized once and can easily do so again. There is not a gray area to be seen between these realms, no hint of shading on the border: one is civilized and adheres to civilized formal war, or one does not.
It is a life and death decision.
One not forced upon any individual but chosen freely each and every moment of every day, and only once one steps from civilized action does the choice to return get barred.
It is hard work to remain civilized.
Sad that there are those who seek to legitimize savagery.
No good shall ever come of that.