A criminal syndicate of Klingons and former Federation personnel on the mining world Cajitar IV, which tried to restart the Klingon war because peace had ruined its profits.
The Broken Circle is the organisation at the centre of the Strange New Worlds second-season opener, also titled The Broken Circle. Its members, drawn from both sides of the recent war, made fortunes from the dilithium of Cajitar IV while the fighting lasted and have lost them since.
La'an Noonien-Singh stumbles on the plot and sends a distress call, and Spock takes the Enterprise out of spacedock without authorisation to answer it. The syndicate has secretly built a ship that looks like a Federation vessel and means to use it to attack a Klingon cruiser, provoking a new war.
Doctor M'Benga and Nurse Chapel are taken aboard it and fight their way out, and the Enterprise destroys the false starship. Spock then smooths matters with the Klingon captain over a barrel of bloodwine.