Enip was a planet a Starfleet Special Operations team from the USS Prospect infiltrated sometime prior to 2367 in an effort to determine if the Enipians were building weapons to attack the Federation. The mission was a failure, with Kari Eriksson and Vanessa Biondo captured, Daniel Radke and Anne Lansing trapped in the caves under one of the main cities, and the rest of the team dead. (Star Trek: The Prospect Chronicles: "Lady Lazarus")

The away team was obviously saved somehow. The author intended Enip to be a Cardassian ally, and the weapons building were not for the Enipians but the Cardassians, as part of the build-up mentioned in Star Trek: The Next Generation episode, "The Wounded".
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