A Cardassian attack on the Federation outpost on Setlik III during the Federation-Cardassian War, killing many civilians and shaping the lives of Miles O'Brien and Benjamin Maxwell.
The Setlik III massacre was a Cardassian assault on a Federation outpost on the planet Setlik III during the long Federation-Cardassian War. The Cardassians believed the outpost was being used as a staging base for an attack on them, and their raid killed many of the civilians living there.
The massacre is first mentioned in the episode The Wounded, in which Captain Benjamin Maxwell of the USS Phoenix launches unauthorised attacks on Cardassian targets after the war has ended. His wife and children were among those killed on Setlik III, and he refuses to believe the Cardassians are honouring the peace. Miles O'Brien, who served under Maxwell and fought in the battle that followed the massacre, helps talk him into surrender.
In Deep Space Nine it is revealed that O'Brien was hailed as the hero of Setlik III, and that the experience left him with a lasting bitterness toward Cardassians that he struggles to overcome. The massacre stands as one of the defining wounds of the war between the two powers.