| Date: | 2399 – 2403 |
| Cause: | Percieved Undine infiltration of Gorn leadership |
| Result: | Annexation of the Gorn Hegemony into the Klingon Empire. |
 Klingon Empire |
 Gorn Hegemony |
The Klingon-Gorn War was a four-year invasion of the Gorn Hegemony by the Klingon Empire that began in 2399, though the two powers had been clashing for more than a decade before. The war ended with the fall of Gornar in 2403, and the Hegemony was subjugated by the Klingons.
Early Conflict[ | ]
Gornar, the Gorn homeworld.
- 2384:
- A Gorn ship attacks the I.K.S. Quv in the space between the Hegemony and the Empire without orders. 207 Klingons are killed and King Xrathis refuses to surrender the survivors. In response, Chancellor Martok sends additional ships to the border and expels all Gorn diplomats.
- 2389:
- Klingon attacks on Gorn systems and ships become more frequent.
- 2390:
- The United Federation of Planets offers to mediate peace talks between the Klingons and the Gorn at a neutral location. Klingon Chancellor Martok responds that the Klingons will not participate in any negotiations until Starfleet withdraws all of its ships from the Romulan-Klingon border. The Federation Council eventually agrees.
- 2391:
- Representatives from the Klingons, Gorn and Nausicaans converge on Deep Space K-7 for the conference, and the Federation sends some of its most celebrated diplomats to oversee the talks. Unfortunately, the peace talks end following the detonation of a bomb that seriously injures Ambassador Zogozin of the Gorn.
- 2392:
- Another peace conference is held, but it also fails when the Gorn begin an invasion of Ogat, a Klingon colony.
- 2393:
- Martok is deposed by Councilor J'mpok, who kills him and declares himself the new Chancellor.
- 2394:
- The Klingons form an alliance with the Orion Syndicate.
- 2395:
- It is discovered that the Undine are actively infiltrating every major political entity in the Alpha and Beta quadrants.
- 2398:
- The third Klingon-Gorn peace summit is interrupted by another bombing which kills Klingon ambassador K'mtok. The Klingon and Gorn governments refuse to participate in any more peace talks.
Full-scale invasion[ | ]
- 2399:
- The Klingon begin a massive invasion of Gorn space after Captain Ja'rod of the I.K.S. Kang provides the High Council with evidence that the Hegemony's government is under direct control of the Undine.
- The Federation Council condemns the invasion, and in response J'mpok pulls the Empire out of the Khitomer Accords.
- 2401:
- A number of current and former Starfleet officers including Ambassador Worf, Admirals Beverly Crusher, Kathryn Janeway and Chakotay and retired Captains Ezri Dax and Tuvok appeal to the Federation Council to reconsider its position on the Klingon-Gorn conflict. The Council refuses to change its stance.
- 2402:
- The Klingons breach the Gorn lines and blockade their homeworld, Gornar.
A Klingon space station orbiting Gornar.
- 2403:
- The network of transport inhibitors protecting Gornar finally fails, allowing the Klingons to conquer and occupy the planet.
- After arriving on Gornar, J'mpok orders a global broadcast during which the Klingons reveal that the Gorn prime minister, head of military intelligence and multiple other high-ranking government officials are Undine infiltrators. The infiltrators are then immediately executed.
- J'mpok then offers the Hegemony self-rule as long as it swears fealty to the Klingon Empire. King Slathis agrees, and receives a non-voting seat on the High Council.