As Walter Wink has pointed out, violence is a tool that allows us to realize certain outcomes that seem desirable to us: to change either the person we inflict it on, or those around them, by 'making an example' of them. Resorting to violence as a matter of policy (as our current justice system does) presupposes that people willingly act badly, so that there's no point trying to change their thinking: all we can do is declare undesirable behaviors 'punishable offenses,' so that the 'bad people' will have 'reasons' to not do the thing. Yet, as Marshall Rosenberg has noted, if fostering lasting behavioral in people is our aim, then violence never works, because while people may comply, they lack intrinsic motivation to act differently. For that, we need to ask -- and care about -- why people choose to harm others, so that we can to try and show them ways to meet their own needs in ways that don't involve harm to others.*
That said, we currently live in states and societies in which the use of institutionalized violence is accepted as normal. Which is to say that most of the time, most people are unaware of the fact that our institutions are blind or indifferent to this violence that is inflicted (unless they happen to belong to the groups that are particularly targeted for repression or exploitation).
The main reason why we don't see this, is because we are socialized not to object to it, and to rationalize the violence as 'necessary'. As such, most of us don't object on principle when we or others demonize individuals and groups as 'deserving' of, or 'needing' to be punished or oppressed, and we're even willing to contribute our labor to the maintenance of oppression and exploitation.
As I've explained in other posts (e.g. here, here, here), there are a lot of factors that contribute to our accepting and supporting that we organize our societies this way. What I want to focus on in this post, is how specific ways of talking and thinking about issues and the people affected obfuscate this violence, and about how the use of 'bureaucratic language' relates to (and is a form of) violence, due to its consequences for how we behave and treat others (and ourselves). I'll illustrate this by explaining how this applies to declarations of war, and other forms of terrorism.
There are a few different ways to define violence, which are all related to one another. To start, there is tangible, physical violence, and the question how this relates to use of force generally. When such violence is employed, it's usually to teach people 'lessons', to punish them, or because some important goal supposedly 'requires' it, or makes it 'unavoidable' (including maintenance of a status quo). Sometimes the person on which the violence is inflicted is also the person who is being 'taught' said lesson, but more often than not, the audience is third parties, while the victim's suffering is merely a means, and the victim's equal needs (for bodily integrity, security, to live) are dismissed as irrelevant.
The second form is bureaucratic-linguistic violence, which has two sides to it. One side involves moral reductionism or essentialism: reducing people to titles, while ignoring most of what makes them human. This can range from defining someone in terms of their vocation or job ('teacher', 'nurse', 'manager') to more insidious stuff, like not caring very much about things that happen to someone because we view them as an 'enemy' or as 'lesser' -- e.g., discounting violence because someone 'had it coming', because they're 'black,' or 'Muslim', because they're 'racist', or 'trailer trash' that got themselves killed by 'choosing that profession'. The other side revolves around denial of agency, and a refusal to think outside of the boxes formed by the rules that govern the game, job or role pattern we're currently engaging in. For instance, thinking 'like a guard', and refusing to acknowledge that we can act differently, and that we aren't our role, but autonomous human beings. Or conversely, thinking we must respond a certain way to something someone does because of how we view them, or because of what we think they expect of us (e.g. feeling afraid to show our humanity while at work 'because work requires professionalism').
A special form of this is single-minded demonization of the type we engage in to 'justify' or 'necessitate' wars, including invasions. That is, deliberately telling lies of commission or omission about certain groups, suggesting that an entire group must be 'punished' because of the actions of a 'leader', for the purpose of giving people the idea that they don't deserve to live, or that they really are 'no more' than racists, (mass) murderers, or what have you. This is highly misleading as well as problematic because of how it makes it easier for us to inflict violence on them, either as punishment or to 'stop' or 'free' them from their leaders (who we wish to replace with leaders who are friendlier to us).
Thirdly, there's the issue of institutional -- and bureaucratic -- violence. Examples abound, but to name a few: (selectively) denying people service, Prohibition 2.0, selectively enforcing laws; rewarding or punishing, listening to or denying people voice based on their titles or credentials (either because the kinds of knowledge or experience they possess are deemed 'irrelevant'; or because the petitioner is, say, a 'slave,' 'black', a 'woman', 'trailer trash' or a 'child'); not aiding someone because they lack insurance or means, or because helping with something other than what you're hired or paid for is 'not your job'). While these interactions can seem one on one, they usually occur within a broader institutional context, and tend to be (re)produced over and over by people acting out the roles they've taken on.
To illustrate how these aspects interrelate, consider this relatively simple and everyday example: children grouping up to beat someone because they believe them to be deserving of punishment for "being" [nothing more than a] 'Muslim', 'black', 'weird', a 'girl' -- or simply a 'loser' who gets beaten a lot [by people like them] -- and getting away with it because the victim (or the institutions) thinks they did something to deserve it, or because of parental institutional access, or 'social status' differences generally. As you can readily see if you unpack this example along the lines I suggested above, all three of the above forms of violence heavily rely on each other to blind us to the fact that we're harming others.
Nearly everyone is taught to accept the notion that once 'their' government -- a highly bureaucratic institutional amalgam -- declares war, those it declares war on -- usually human beings who are part of a 'different nation' -- become 'their' enemy, whose rights to life are forfeit. This is usually 'justified' by referencing the behavior of those others, which is interpreted as 'aggressive' or 'threatening', while (even today) we generally see 'our' invasions and aggression as either 'preventive' -- a legally insane notion --, or as well-intended, leading us to take a violent response by the population whose lands we occupy as 'proof' of their unreasonableness.
On a moral level, this of course is completely indefensible, as we simply don't have the right to declare another's life worthless, or to instrumentalize someone -- that is, to kill someone for the purpose of hurting someone who cares about them (consider how the lives of Job's children have no value except insofar as Job cares about them). So what is going here? Why do we accept it when institutions decide for us that we should not value and terrorize and kill other people, and that we should risk our own lives in the process? And more importantly: why do so many of us accept that it's okay in principle to terrorize and kill other human beings simply because of who or what they supposedly are (or are doing); what administrative unit they belong to, or who they will stand with or defend?
A few (arguably superficial) ways how we get ourselves to accept this, is via belief that we 'owe' our country -- or 'our' leaders -- our trust, or via 'they will do the same to us...'. But there's got to be more to it than that. After all, if someone announces they want to kill us, we may still choose not to use deadly force ourselves, and not to goad them, or to attack "any yellow dwarf with a pocket knife." Yet in the case of conflicts between nations, it seems to be pretty normal to use lethal force to 'defend one's interests' (including when those interests are purely economic, or when -- in Vietnam and Grenada's case -- the only aim is to make a point: that we're perfectly happy to use overwhelming force to enforce capitalist development). Moreover, there's the fact that as soon as war is declared, and often starting much earlier, the media will only publish stories -- including outright lies -- that add to the fear and/or outrage, while barring the publication of anything else, and calling those who do otherwise disloyal or 'apologists' (effectively for reminding readers of the enemy's shared humanity). In sum, why do our media work this way, and why do most of us accept the fact that they engage in such transparent attempts at demonization? Are we really that callous, or is this mentality carefully constructed and maintained via this process of selectively paying attention to and ignoring certain events, and by reporting on them in the way that the media do, because otherwise we'd object?
On the other hand, most of the time, people are pretty uncomfortable both accepting that their country goes to war, and with the decision that they should personally contribute to violence on those others. By way of illustrations, recall that the US government had to orchestrate a huge propaganda campaign to get US citizens on board with participating in World War 1, consider how the "draft" was mandatory for a reason, that "desertion" is (and has to be) heavily penalized, and that some people nevertheless conscientiously object, consider how the people who manned the trenches during the winter of 1914 basically stopped playing their role for a while, and how soldiers in (that completely immoral war) would kill their commanding officers. In sum, most people do have to be "convinced" to accept a declaration of war, beyond through demonization.
One way the state can try to work around this 'problem' is to play on use people's sensitivity to extrinsic rewards, and to only use professional armies or mercenaries (currently usually called "contractors"), so that it can use people who've best internalized the requisite values to perform the worst of the violence. (As an aside, this is a large part of how Ancient Greece rose to prominence, and where Alexander got his army -- the Greeks hired themselves out to Persia to enrich themselves by killing others until they had enough to start conquering.)
Another way of doing so, aside from demonizing specific others, is to generally inflate the subjective threat level, by constantly feeding fear. There are many ways to feed it, but declaring a "global war" on "terror(ism)" certainly is one strategy that's paid off. This way of going about it is especially useful because it depersonalizes the war, given that you declare war on ideas and behavior, rather than on actual persons or groups. This works both because you can then "attack the problem from different angles" (while the state terror you inflict generates a steady stream of people who come to share your view that it's okay to use violence to reach your goals, and start to use violence in return, that you can use to justify the 'war'), and because it serves to insulate the war from criticism (such as that it reeks of racism or genocide to constantly be killing Muslims or non-white people who live on top of resources you want, and who you've essentialized as bad-because-'terrorists', 'drug traffickers' and salespeople (in that other 'war'), and so on, while whole armies of (racist) talking heads favoring regime change constantly demonize the people you're attacking or planning to attack). And so violence is constantly repackaged and perpetuated, with one feeding the other, abroad as well as domestically.
Yes, there are some cases in which war may be unavoidable. But in the overwhelming majority of cases that will come to mind, there were many other, more logical points at which we could've intervened or acted differently that would likely have prevented the outbreak of war, genocide, or what have you. And the reason why we didn't was usually that there was money to be made, or we benefited from the status quo in other ways. And even then, it's highly likely to lead to more of the same, because the mentality that leads us to war, also encourages other forms of oppression, exclusion and violence.
* Do note that this may have far-reaching consequences, especially in a context like our own. E.g. if people steal to make a living, in a meritocratic society which is built on structural violence, it's not much of a leap for certain individuals to conclude that they may do the same, if their needs don't matter, and if they're marginalized. So if we want to address this, we need to do something about institutionalized inequality; because without it, we have no leg to stand on.