Bellamy's mouth draws into a thin line, unimpressed with whatever it is he's meant to make of her tone.

"I'm not a sir." Important correction. He folds his arms over his chest. As eager as he is to get to the books, he's also determined to dig in, stubbornness momentarily outweighing his curiosity. "And yeah. I can be more specific. I'm interested in historical battles. Warfare. That kind of thing. Big campaigns, wars... the way troops were trained by people that don't exist anymore. And people who do. Specific enough for you?"

If he's gruff about it, it'll go a long way to cover childish eagerness.