Since K'Nes calendars weren't standardized until after the empire took hold, it's uncertain when exactly the Tor - or "empire" - arose. Sometime in Earth's 20th or 21st Century, the leader of a great trading house on Purrfang, named Horrath, managed to buy hyperspace technology from the Jurvain, who made first contact with the K'Nes. With a monopoly of space travel, Horrath became incredibly wealthy. He used his wealth to buy controlling shares in all of his major competitors. When there was general disdain against Horrath's measures, he made a deal. He would form a government and exact taxes - far cheaper than paying dividends - but he retained the rights to space travel. So he became Emperor Horrath I of the K'Nes Tor.
Expansion of the Empire
As the emperors were more established, they weakened their monopoly on space travel, and the K'Nes expanded into additional systems. In 2178, they made contact with the Earth Federation, and opened up trade relations with humans. They were too far away to be affected by the Bug War, but made extensive profit from supporting those attacked by the Arachnids. Unfortunately, their low birth rate meant that K'Nes expansion was slow. The Federation expanded into the galactic east faster than their 'cat neighbors, starting in 2210 with the corporate colony of St. Michael's Star. Hence they are forced to sign the Treaty of Midgar in 2218, negotiating two additional systems to the two they already possessed, and ceding rights to all others to the humans.
3rd Civil War
The Treaty of Midgar was unpopular with K'Nes nationalists who believed that they needed more room to expand. This pressure forced the emperors to build their war fleet, waiting for an opportunity to expand. That chance came in 2243. With the Federation fractured, Emperor Horrath VI ordered the invasion of human space. They initially had some successes, and were able to seize Andersvald and Midgar. They proceeded on to New Tokyo when their fleet was destroyed by the Orb wielded by Xavier Pollos.
That ended their war effort. When they met with all factions to sign the Treaty of Wilke's Star in 2244, they annexed the two systems into the empire.
Fall of the Empire
Although they were lucky enough to be distant from the Vin Shriak and the 1st Vulthra Wars, Emperor Horrath VI decided to add to their victories by allying against the Earth Federation in the 2nd Vulthra War. Believing that the Fed was weak from so many wars, they hoped to gain more ground. Unfortunately, their inexperienced fleet wasn't able to handle the veteran Earth Fleet, and was destroyed in the Battle of Andersvald. The K'Nes front crumbled after that and Chairman Clarke officially annexed them into the Federation in 2257. For the next eight years, K'Nes society underwent massive upheavals during the human Occupation.
Behind the Scenes
The K'Nes as well as the Jurvain were added by Marcus to the political landscape as a way to add more aliens to the TI universe. Unable to remember which races Nathan Bax had added, Marcus made up the empire.