He's not sure how to respond to the personal information she's giving him. So he keeps it short, but truthful.

'That's admirable Chris.'

He sips at his drink. 'I was in the Navy during the war and for a while afterwards - had to do something when I left. Decided to stay with the government.'

If he decided to explain the whole thing, they'd be there for hours. And he's just not into sharing, not so soon after meeting somone anyway.