Where does the officers corps of the imperial army in Star Wars come from? In the prequels the Clone Wars are fought entirely by Jedi, drones, and the clone forebears of storm troopers. The clones even have separate names, ranks, responsibilities. But at the end of Sith Tarkin is overseeing construction of the Death Star, dudes have uniforms, rank, a whole bureaucratic substructure independent of the Senate, the Jedi, even Vader. And there's no sense at all of the storm troopers in the Original Trilogy having any kind of officer corps.
Part of the drama of the original trilogy is the tension between Vader and the uniformed non-clone military. Also, the fleet is composed along racist lines: no unhelmeted clones, no non-Caucasian aliens. (The Bounty Hunters are dismissed as "scum.") Where do these guys come from? Are they conscripts? The mobilized remains of a brownshirted imperial militia?
Along with the retarded faceless droid armies in Phantom Menace and after, not exploring the encroaching militarism of the Empire is a serious oversight. It's not just a political failure that produces the empire -- it's the seizure of the mechanisms of force and the elimination of the Jedi as a competitor on the legitimate use of violence. As someone interested in how armies work, and fictional representations of soldiers and officers, I love the intimations in the OT and feel that very large gap in that part of the story.
Armies I think have to be seen as an emerging theme of the comics as well, and in some sense superhero stories are inherently anti-military. Obviously the recent Iron Man film addresses this head-on, but you also have The Hulk, Captain America, Nick Fury and SHIELD, and so on.
There is a utopian imagination at work whereby we seem to dream of a world where right-minded, ultrapowerful civil servants (whether Supermen or Jedi) eliminate the need for standing armies, traditional manifestations of force, and hostile international/intergalactic relations.
The great counterexample might be the Green Lantern Corps, a kind of armed invisible UN that is designed to keep the peace but also act as a kind of nuclear deterrent against interplanetary (as opposed to merely global and local) aggression. The Green Lanterns effectively seem to recognize each planet/sector as sovereign and world wars as local affairs in which they need not interfere.
And so, as with Star Trek, international or interethnic conflicts get allegorized as conflicts between actual aliens, while Superman, Batman, and friends are available to deal with local petty crime.
Star Wars may be the only manifestation of an honest-to-goodness civil war where the conflict between superhuman beings (the Sith and Jedi) are played against the backdrop of a purely human conflict between two organized armies. The events intersect but they do not determine one another. Even the destruction of the second Death Star has nothing to do with the Jedi or the Force really; it's Ewoks and rebels killing storm troopers, and a non-Force wielding fleet whomping the Death Star and Imperial troops.
So: how do these armies get started? (The rebel army is even more of a mystery.)