The Federation-Tarn War (also known by the Tarns as the War of Federation Aggression) was an interstellar conflict fought between the newly formed United Federation of Planets and the Tarn Empire between 2160s and 2165.
- Since the Federation was founded in 2161, the unknown start date for the conflict would be sometime after this date.
Prior to their encounter with the Federation, the Tarn were permitted the honor of exploring new territories, mapping out sectors of unclaimed space and attaining glory for their circle. Some Tarn viewed that a war with the Federation was merely an extension of this.
War was never officially declared in this conflict. How the war was started or what happened with the first contact between the two powers was never revealed. However the legends of this war and the battles fought would be remembered until 2367.
During the war the USS Constitution was answering a distress call when a vessel from the Tarn Imperial Fleet appeared and opened fire. Two hundred Constitution crewmembers were killed, including Geordi La Forge's ancestor, Ensign La Forge. It was later revealed that the distress call was a ruse to attract the vessel into the Tarn's range, although the Tarn defend their attack as a necessary step to prevent the Constitution from reinforcing combatants fighting Tarn starships at the front lines of the conflict.
Unknown to either side until 2367, the Starfleet vessel USS Verdun and the Imperial vessel Rashasa met in battle in the Torgu-Va system in 2163. The two starships caused enough damage that both opponents had to abandon ship. The survivors from the two vessels traveled to the lone planet in the system, Torgu-Va.
In 2165 the Tarn knew they couldn't beat the Federation in a stand up fight and the Federation wasn't interested in a dragged out conflict. Both sides agreed to a cease-fire and to cordon off a couple of hundred thousand cubic parsecs as a neutral zone. The region, now called the Tarn Neutral Zone, was known to be devoid of sentient life before the zone was established. The neutral zone effectively closed the discussion as to who was at fault for the start of the war and no permanent treaty was ever established between the two governments.
The Tarn ruling circle that was in power at the end of the war fell out of favor and was no longer the First Circle in the Council of Circles for agreeing to the cease-fire. Many Tarn believed that the new neutral zone was established to box in the Tarn Empire. The scars on both sides would run deep and even two-hundred years later tensions ran high between the two powers.
Just before 2367, elements in both governments started a dialog and eventually the Tarn Neutral Zone was opened to ships on both sides. Starfleet sent the USS Enterprise (NCC-1701-D), with the Tarn delegate Harna Karish to observe, to fly the flag and to scan this area. There they discovered the descendants of the Rashasa and Verdun on Torgu-Va, still fighting the Federation-Tarn War over two-hundred years after a cease-fire had been called. News of this conflict spread through out the Tarn Empire and Federation, threatening to envelop the two powers into a new shooting war. Luckily some unusual diplomacy by Captain Jean-Luc Picard and Admiral Garu Jord resolved the issue before the conflict spread.