Honestly, I'm having some difficulty thinking about how Kas would know him other than "The guy who commands the military." I mean, as an Assassin, he's more likely to know the Spymaster than the Commander personally, but then, Kas has been in The Inquisition for about eight years, so they've probably crossed paths more than once or twice...I'm thinking that the Commander knows who Kas is, and has likely employed his talents once or twice, but they aren't exactly "Dinner Friends." Haha.