I think one of the best examinations of this question was Robert Heinlein's Starship Troopers. Not the execrable film, but the much different novel. The basic premise of the novel is never stated overtly, though every detail you need to discern it is: What would happen to a nascent space-faring Earth if it faced a prolonged existential threat from offworld? Heinlein's answer was that the world would join together against it, and eventually, of necessity, develop a democratic stratocracy: Service is not compulsory, but only those in service can vote, which creates an obvious incentive.

The point of a stratocracy is that it eliminates the political step between military strategy and execution -- the military is the government, so there's no fucking around in chambers while politicians try to understand what the military is thinking, and then change their plans, or wait too long to execute them, or change them so much that they don't work.

The downside, of course, is that there's little or no political counterpart to military goals. Normally -- and very appropriately -- that's to be avoided in any society that doesn't plan to spend all of their time at war. But in the case of Starship Troopers, the society is in a constant state of war, has been for a long time, with no end in sight, and the threat is existential: The fate of their society, even their very survival, depends on a sustained, robust, effective military posture. With those being the stakes, the society yields to the obvious need.

Heinlein's concept tempers this somewhat with an underlying democracy that somehow does guide government policy -- presumably, if necessary, over and above the objections of the military. However, the franchise goes only to servicemen or veterans. So this deimos quite obviously leans very heavily to military views.

There are many ways to style a stratocracy, and Heinlein's vision is only one of what must be countless variations, many of which would be very different. I would trust your instinct on that. But that novel is a pretty good introduction to the concept.