If this could be considered a first person impression, I'd be 100% hardcore!
"...There were a few men in every organization who engaged in no pastimes and joined in no social intercourse. These men were irreproachable as soldiers, it may have been, doing without grumbling everything that was expected of them in the line of military or fatigue duty, but they seemed shut up within an impenetrable shell, and would lie on their blankets silent while all others joined in the social round; or, perhaps, would get up and go out of the tent as if its lively social atmosphere was uncongenial, and walk up and down the parade or company street alone. Should you address them, they would answer pleasantly, but in mono-syllables; and if the conversation was continued, it must be done in the same way. They could not be drawn out. They would cook by themselves, eat by themselves, camp by themselves on the march, --in fact, keep by themselves at all times as much as possible. Guard duty was the one occupation which seemed most suited to their natures, for it provided them with the exclusiveness and comparative solitude that their peculiar mental condition craved."
John D. Billings, Hardtack & Coffee: The Unwritten Story of Army Life, 1887