This episode of "Star Trek: Deep Space 9" is unusual in several ways. Instead of the usual two plots, there is only one. Additionally, the show is grittier and more violent than usual.
There is a Federation base on AR-558--a place that used to be under Dominion control. It's recently been under siege for some time and the Federation troops there are disheartened and beaten up pretty badly. So, when Sisko and some of his folks arrive, they are very welcome. But the task of keeping this base seems impossible, as only about a third of the original troops are alive.
An interesting guest star in this one is Billy Mumy, as he was once a regular on "Lost in Space" and was a regular on "Babylon 5" when he made this guest appearance. Overall, a decent episode, though I did feel their attempt to be grittier still felt amazingly sanitized compared to real warfare. Still, it's worth seeing.