Searching for sources: Loss of humanity due to violence experience

[GenosseGeneral]

Fellow members of the .org,
I am about to write an essay about "the loss of humanity because of inurement to violence". The basis is an excerpt of a speech of Cicero, in which he complains about the loss of humanity in Roman society due to the civil wars and proscriptions.
I am looking for any kind of research on that topic.
If you know any sources from antiquity on this, although I doubt that there any or modern sources dealing with antiquity. Of interest is also the modern period, for example research on veterans from Vietnam, or even better if available, Iraq.
Sources have to be in English or German, I am also skilled at latin if there sources from antiquity.

If you have any additional questions, please ask.

Thanks in advance
GenosseGeneral

[PanzerJaeger]

Here, and specifically here. I cannot speak to the editorial perspective of the author or the thoroughness of his sources, but he does tend to draw on many of them which should at least be helpful.

[CountArach]

Do you mean humanity in the physical sense of lives lost or do you mean humanity at the conceptual level (I guess humanitas, as I suspect Cicero said)? If it is the second of these then you might want to see Livy's preface:

The subjects to which I would ask each of my readers to devote his earnest attention are these - the life and morals of the community; the men and the qualities by which through domestic policy and foreign war dominion was won and extended. Then as the standard of morality gradually lowers, let him follow the decay of the national character, observing how at first it slowly sinks, then slips downward more and more rapidly, and finally begins to plunge into headlong ruin, until he reaches these days, in which we can bear neither our diseases nor their remedies.

This is definitely in answer to Sallust's own Preface in the Bellum Catalinae:

But when our country had grown great through toil and the practice of justice, when great kings had been vanquished in war, savage tribes and mighty peoples subdued by force of arms, when Carthage, the rival of Rome's sway, had perished root and branch, and all seas and lands were open, then Fortune began to grow cruel and to bring confusion into all our affairs. Those who had found it easy to bear hardship and dangers, anxiety and adversity, found leisure and wealth, desirable under other circumstances, a burden and a curse. Hence the lust for money first, then for power, grew upon them; these were, I may say, the root of all evils. For avarice destroyed honour, integrity, and all other noble qualities; taught in their place insolence, cruelty, to neglect the gods, to set a price on everything. Ambition drove many men to become false; to have one thought locked in the breast, another ready on the tongue; to value friendships and enmities not on their merits but by the standard of self-interest, and to show a good front rather than a good heart. At first these vices grew slowly, from time to time they were punished; finally, when the disease had spread like a deadly plague, the state was changed and a government second to none in equity and excellence became cruel and intolerable.

As well as this quote which I suspect will be useful for you:

Lucius Catiline, scion of a noble family, had great vigour both of mind and body, but an evil and depraved nature. From youth up he revelled in civil wars, murder, pillage, and political dissension, and amid these he spent his early manhood. His body could endure hunger, cold and want of sleep to an incredible degree; his mind was reckless, cunning, treacherous, capable of any form of pretence or concealment. Covetous of others' possessions, he was prodigal of his own; he was violent in his passions. He possessed a certain amount of eloquence, but little discretion. His disordered mind ever craved the monstrous, incredible, gigantic.

After the domination of Lucius Sulla the man had been seized with a mighty desire of getting control of the government, recking little by what manner he should achieve it, provided he made himself supreme. His haughty spirit was goaded more and more every day by poverty and a sense of guilt, both of which he had augmented by the practices of which I have already spoken. He was spurred on, also, by the corruption of the public morals, which were being ruined by two great evils of an opposite character, extravagance and avarice.

Roman historians were always concerned about a general decline in Roman morality (of which humanitas was a part) and were always trying to pin-point the moment that it happened. Woodman's book Rhetoric in Classical Historiography (pp. 124-128) describes Sallust's attitudes quite well and how he really began this process.

[Fragony]

Mutiny on the Batavia might be worth looking into, real life Lord of the Flies. Stranded surivors turning into killers for the sake of killing, it's quite incredible what happened there