We are again living in an age of religious Holy wars, as contrasted to wars from the previous century that while definitely differentiating between the forces of "us" vs. the forces of "them", weren't fought for the sake of the satiation of their respective god, but typically for the aggrandizement of one nation in conjunction with the forceful oppression of another nation and its people. Most of the time within any war, there is almost always a call to demonize the opposition in order to fire up your troops. When this is combined with the color of religion, so as to act as some sort of moral justification for your declaration of war, the boundaries of decency are often crossed. Often too, through the apparent sanction of your religion, this "holy war" will become a sort of divine retribution against infidels, or apostates, or "blue-eyed devils", or savages. If you then add the supposed awards that will be bestowed upon your "freedom fighters", that if not in this world, but in the world to come, will soon be theirs, you have the makings of fanaticism. Further to this point, if your call to arms, is based around the protection of your people and its beliefs, along with the communal sounding call being rung against those that you are led to believe are on the cusp of wresting those very things away from you and your family, you very well might felt obligated to stop at nothing and to contemplate doing just about anything to protect your own and to avenge your people.
While one nation fighting against another nation may become satiated and satisfied at some point, or even to willingly go to the negotiation table to come to terms, those that believe that their calling is both divine and pre-ordained are not likely to stop short of annihilation or physical death. This means that those that claim to speak for God or for a prophet of God in such a manner, that their ultimate objective is that you either must surrender to their particular faith and its attendant ideology, or if not, be put to the sword is both fundamentally flawed but also, by definition, in ethical error.
There is no legitimate religion, nor any interpretation of a legitimate religion, that has as its core premise, that you must believe in its tenets to such an extent that your free will and your free choice must be suppressed to a manner that makes you an automaton or a mindless puppet. A man, is not made to be trained as an animal or to yield his mind to others for nefarious purposes, because the purpose of a man is made to serve God and his fellow mankind as an equally created being, and not to destroy mankind or to corrupt the love of an immutable God.
Christ as well as other great prophets has made it clear, that their kingdom is not of this world. Man fights for what? So that one man can rule or take from another man, and all for what? So that one man has more possessions than another? So that one man can command that all others believe some certain dogma, willingly or not, but in the end this gets you what? All of this killing, all of this strife, all of this misery and hatred, will not bring you peace, not in this world, and certainly not in the next. Satan offered Christ dominion over all earthly kingdoms, yet He did not take it, He could not, because Christ knew that earth is a proving ground and nothing more.
There is never a need or a good reason for a religious Holy war on this earth and there never will be. Our Creator is sovereign of all and is never in danger whatsoever; His only wish is that we listen to that still small voice inside of us that tells us that we are all sons and daughters, created by the same Hand of God.