Star Trek: Deep Space Nine
Episode: DS9 433 - Armageddon Game

Planet: name unspecified. Humanoid, advanced space-faring species, native to the Alpha Quadrant. Having just ended a centuries-old war with the T'Lani, which included use of the Harvester non-biogenic weapon, the two sides in 2370 were so bent on peace at all costs that they eliminated all signs of the weapons, including the deaths of their own scientists and the Federation help called in, Dr. Bashir and Chief O'Brien from DS9. Their technology included transporters, energy-beam weapons of some kind, and sensors, with a biomedical knowledge equal to the T'Lani but not as advanced as the Federation.