Yes now they have started sending civilians on foreign courses, previously only army people used to go which is a good change. And no not all army people leave, those who specialize in intelligence courses always stick with it even after their retirement from military and trust me they are way over in numbers as compared to civilians. I don't agree with the notion that a civilian knows more, not that i care who knows more but its not a fact at all. DG ISI is an army man and the rest of the significant sects in ISI are also headed by Major Generals, there is no way a civilian who cant even head a sect knows more.