The Klingons have the KDF..."Klingon Defense Force" fleet. The Klingons, for one race, are not too concerned with scientific knowledge beyond that which advances their empire and it capabilities. Similar are the Romulans, only more sneaky and devious. they're th eones, after all, who developed the Cloaking Device and the Bird-of-Prey concept ship, both likely obtained by the Klingons in the brief Romulan-Klingon alliance of 2268-70. That's also how the Romulans ended up with D-7 Class Klingon Battlecruisers; at least, that's the official story. The real story was that the show couldn't afford any more models, and they wanted bigger, more vicious-looking ships for the Romulans.+LOL+
As a lifelong Star Trek viewer, Starfleet is the only entity I know of defending and expanding the Federation.
They're the scientific, exploratory, tactical and defensive body for the entire Federation. Of course, there are thousands of ships in the fleet, including battleships; the Dreadnaught Class. They're relatively short-range, from what I gather, heavily armed and shielded, of course, and are stationed at Starbases and outposts in the sectors they defend, much like the Navy (Pacific Fleet, Atlantic Fleet, Persian Gulf, etc.).
That's how I see it.