Mordan IV is a planet scarred by a decades-long civil war that began after Admiral Mark Jameson secretly armed both sides.
Mordan IV is the planet at the centre of Too Short a Season. Decades earlier Admiral Mark Jameson had negotiated the release of hostages there, but he did so by supplying weapons to both factions, which led to a long and bloody civil war.
When Governor Karnas reported a new hostage crisis and asked for Jameson, the Enterprise brought the elderly admiral back to the planet. The crisis had been staged by Karnas to lure him there. Jameson died on Mordan IV after his attempt to make amends, and the hostages were released.