Maes's approach would probably be slow -- chatting up guards and being friendly with them. Buy'em a drink, ask about their family, anything to make them not see him as a threat. He'd gush about his own family too to help ease their suspicions (if there were any to be had). Since it'd be a slower approach, he'd probably also focus on one or two guards specifically so he could build that rapport with them. Eventually he'd probably start fishing for information about the hierarchy here since he was military himself, pose it as a "let's talk about how much it sucks to be a foot soldier" and things like that. So he'd probably be finding out how everyone is ranked, who reports to whom, and then maybe try to start asking after the captain himself.