Ah ok.
You don't seem to be a DS9 fan (you implied it didn't "have a heart"), but your pitch reminds me of the Dominion War arc, where human dynamics during a time of war was pretty well staged. A very specific episode even comes to mind ("The Siege of AR-448"), also set on a moon / planetoid.
I'm also thinking of Outland, in which Sean Connery is taking a last stand all by himself on Io, the Jupiter moon.
Depending on what you want to focus on, you could also find relevant inspiration in non sci-fi works. Since most good sci-fi is all about good characterization, you could check any good war / siege / last stand movie : The Unforgiven (John Huston), Apache Drums (Hugo Fregonese), the director's cut of Kingdom of Heaven, are the first ones that come to mind, but I'm sure there are plenty of others.
Looking in non sci-fi territory could also be the key to getting your project "a heart"...