The analogy to military or civilian intelligence might not be clear-cut, though. Rather, the Tal'shiar could fill a role similar to the political officers of the former USSR, with decided authority over the military, certain lip service to the uniforms and ranks of the military, and nevertheless a civilian base of power.
This would not be a particularly close analogy, either, but possibly a necessary diversification of the more usual analogies... These people are aliens, after all. Then again, they are also pseudo-Romans in some ways, and Rome in most of its eras was famous for its blurred lines between military and civilian organizations and command relationships.
Timo Saloniemi