The ''Defiant'' makes a supply run to planet AR-558, the site of a Dominion communications relay that Starfleet captured. The relay has been under constant siege, with the crew defending it overdue to be relieved by a new crew. Sisko, Bashir, Nog, and Quark find themselves stuck on the planet and having to help hold the relay against a Jem'hadar batallion, while dealing with deadly Dominion booby-traps.

!This episode contains examples of:

* BattleTrophy: Reese keeps a necklace of Ketracel-White tubes hung around his neck. Episode writer Ira Steven Behr called this "about as grisly as we could get on ''Star Trek''".
* BreakTheCutie: Nog gets shot, and his leg is amputated.
* DarkerAndEdgier: One of the darkest episodes of the whole franchise, providing a wholesale {{Deconstruction}} of Roddenberry's vision of an ideal future humanity.
* HoldTheLine: Sisko's order to the remaining troops.
* HumansAreWarriors : At least when you take away their sonic showers.
* ImADoctorNotAPlaceholder: An engineer, not a magician.
* NewMeat: The relief troops at the end.
-->'''Reese:''' Children.
-->'''Sisko:''' Not for long.
* NotSoDifferent: Quark spends a lot of the episode moralizing, but in the end he drops the superior attitude, picks up a phaser, and proves that when push comes to shove he can be just as ruthless as any [[FantasticSlur hew-mon]].
* PapaWolf: Quark was quick to defend his injured nephew in the quickest and most efficient way possible: By shooting the enemy that was about to attack them.
* ParanoiaFuel: The invisible floating mines are a disturbing InUniverse example.
* ShellShockedVeteran: Everyone at AR-558 - they were supposed to be rotated out after 90 days. They've been there five months with no relief and under constant attack to the point they went from 147 troops to just 43 by the time the ''Defiant'' shows up.
* ShoutOut: The battle plays out much like the film ''{{Film/Zulu}}''. There's even a scene where Jem'Hadar are expended merely to test the defenses of the camp (of course, these Jem'Hadar were holograms).
** All of the soldiers stationed on AR-558 were named after characters or actors from the WWII movie ''Hell Is For Heroes''.
* SoldiersAtTheRear: Both engineers, Nog and the poor guy assigned to keep [=AR558=] running.
* SoundtrackDissonance: During the battle
* WarIsHell: This episode shows no glory, no love of battle. Just the harshness and a piece of rock which no one would care about if not for the technology put there.
* YouAreInCommandNow: Lt. Larkin was left in command at AR-558 after Captain Loomis and Commander Parker were killed prior to Sisko's arrival. He takes command as the senior officer when the ''Defiant'' is forced to retreat.