San-Tarah was the sixth planet of a binary star system in the Kavrot sector. It was surrounded with subspace eddies, and was rich in many mineral resources, including kellinite, koltanium, and uridium. The planet was the homeworld of the pre-warp Children of San-Tarah, as well as many other lifeforms, and voluntarily joined the Klingon Empire in 2376.
At some unknown time in the planet's history, a battle took place in orbit. The combatants were using subspace weaponry, and this led to the creation of subspace eddies that encompassed the planet. These eddies masked the planet from long-range sensors and disabled certain technology (such as disruptors). They could also cause significant damage to a ship that drifted too close.
These eddies nearly prevented the IKS Gorkon from noticing the planet during its tour of duty in the Kavrot sector, in 2376. However, the planet was detected by operations officer Lieutenant Toq. Toq was not able to determine much about the planet until the Gorkon penetrated the eddies, but he concluded it was rich in kellinite- one of the resources the Klingon Empire needed after the Dominion War. He also determined that the planet was inhabited by a pre-industrial species, which led to Captain Klag concluding it would be "easy to conquer".
Klag was mistaken, because while the Children of San-Tarah were primitive, they were the ultimate warriors, and had perfected a warrior culture that focused on nothing but battle- no politics and no commerce. They didn't even have a word for peace. So when the Klingon warriors attempted to take the Prime Village, they were routed. The Ruling Pack of the San-Tarah then proposed an alternative: a series of contests pitting the Gorkon crew against the San-Tarah's best warriors. If the Klingons won, the San-Tarah would voluntarily join the Empire. If the San-Tarah won instead, the Klingons would swear never to return. (GKN novel: A Good Day to Die)
The Klingons ultimately lost, and while Klag intended to honor his word, General Talak (the commander of the Kavrot sector fleet) disregarded it and ordered the planet taken over by force. Klag augmented the Gorkon with five other ships from the Order of the Bat'leth and beamed down Klingon warriors to help the San-Tarah defend their world. Talak, on the other hand, had ten ships, including another Qang class ship, the IKS K'mpec, which was commanded by Klag's brother Dorrek.
The two fleets engaged in battle over San-Tarah. The fact that Klag was familiar with the subspace eddies and had developed techniques for firing photon torpedoes (and, eventually, disruptors) provided a huge advantage. In the end, Klag's forces won, General Talak was killed, and Chancellor Martok himself arrived at San-Tarah, where he commended Klag for his actions. It was a destructive battle though, and out of the seventeen ships engaged in battle, only six survived and nearly all would need extensive repairs afterward.