A brutal ground campaign on the moon of J'Gal during the Federation-Klingon War, where Joseph M'Benga and Christine Chapel served in a field hospital and the Klingon general Dak'Rah earned his notoriety.
J'Gal was a moon in Klingon space where Starfleet forces fought alongside local colonists. M'Benga and Chapel met there at a forward medical post under constant fire, treating casualties with too few supplies and at times holding patients in transporter buffers.
The Klingon commander Dak'Rah ordered the killing of civilians, including his own people. He later defected to the Federation and became a celebrated ambassador, claiming to have slain his own officers in remorse.
The Strange New Worlds episode Under the Cloak of War tells the story in flashback when Rah visits the Enterprise in 2259. It emerges that M'Benga, sent in as a covert soldier, killed the officers himself and that Rah fled. Rah dies in a struggle with M'Benga in sickbay.