Vengeance
Star Trek: The Triangle Missions
The USS Niven is host to a flock of admirals set on making a dangerous decision: reactivation of the Doomsday Machine from A Doomsday Like Any Other Part 1 to defeat another Borg Cube. But to avoid upsetting the balance of power in the quadrant, the Romulans would have to be appraised, and Captain Koyanagi and the Niven would be there olive branch.
Overruling Koyanagi's vociferous disagreement, the meeting with the Romulans were tense but ultimately successful. A surprise visit by Emperor Gowron himself led to a joint fleet victory over the Borg. Most surprisingly, the Romulans held strictly to the letters of the agreement. The Borg threat to the Federation was defeated, the Doomsday Machine's was destroyed to restore balance, and Emperor Gowron parlayed his victory into finally ending the Klingon Civil War with Duras' exile.
