For a normal well-adjusted person, it isn't easy to kill anyone at anytime for any reason, especially if that person is unarmed, or defenseless, or old, or a woman, or a child, because doing so, actually killing someone in more or less, cold blood, negates much of what it means to be a conscientious sentient human being to begin with. So too, it is a lot more difficult to kill someone without the aid of a weapon such as a gun or a large knife, because to kill someone with your bare hands or with a hard stone will often necessitate an extraordinary effort and a sustained desire to do so, in addition to the fact that the person that you are trying to kill, will most likely be trying to protect, defend, or to escape, so then to accomplish such a killing task, is exhausting from a physical standpoint. But, it also is exhausting from a mental standpoint, because this is all happening in real time, with real humans, at very close proximity, which is basically a form of purposeful fratricide, which means that if somehow you can addle your mind so that you don't consciously recognize that you are killing a fellow human being, or convince yourself that the person being extinguished by your hands is not fully human, or is less than human, or demonized that person in some way, than it becomes easier to accomplish the task at hand.
This means, that military operations know that hand-to-hand combat is something to be avoided at all costs, not only because the resulting kill ratio will be distressingly low, but that it also takes a very large psychological toll on the participants, so having weapons, sophisticated weapons, makes killing other human beings, a lot easier because it can be done at a distance, in which as distance increases, the moral qualms of what you are actually accomplishing are significantly reduced, because in your mind, you can begin to proselytize that you aren't really killing people, but that you are simply hitting or engaging"targets" or objects or especially "bad guys", which implies, of course, that you must be one of the "good guys".
Still, Americans don't like to see their own men and women killed or harmed in all of the wars that America gets involved in, so that the military has had to make a significant adjustment since the debacle of Vietnam, which is to utilize far less "boots on the ground" and far more air power, air strikes, heavy artillery, and anything that can rain significant hellish damage upon the opponent without actually endangering American soldiers. Unfortunately, the fundamental problem with bombing and heavy artillery is not that these weapons don't kill, because they do a very good job at killing, but that these weapons are blunt in their killing power, so that whatever is in their target range is going to either get hurt real bad, or die, and that obviously includes civilians, and non-combatants of all ages, male or female.
For instance, as reported by airwars.org, in regards to coalition airstrikes of Syria and Iraq, from August 8, 2014 through September 15, 2017, "…that a minimum of 5,486 to 8,414 civilians are likely to have died in Coalition actions…", of which, America stands accused by recognized international tribunals of no war crimes, whatsoever, while the establishment media in conjunction with the military, spins the tale that they regret any and all overseas civilian deaths, but pushes the lie that in order to get the "bad guys" there will regretfully be some collateral damage. The truth of the matter is that when bombs are dropped, and heavy artillery is fired into known civilian areas, civilians are going to die, and when that is not considered to be a crime against humanity, then that is exactly how you get away with killing thousands of civilians, and because those dropping the bombs do not care to see and do not care to experience their lethal destructive power of their bombs, it is rather easy for them to assuage their conscience by believing the lie, that their mission was for the betterment and safety of the world, but, in truth, it most definitely was not.