The Kilrathi are a race of intelligent, civilized aliens. Their biology is extremely similar to that of Terran mammals, and to human eyes they have a distinctly feline appearance. For thousands of years their civilization has existed as a single fractious, militaristic empire. Based on the concept that the race is perfected both physically and spiritually by warfare, the empire was, historically, a constantly teeming mass of feuds, vendettas and revolutions.
Some time around the dawn of the Terran 23rd century, however, something happened that finally drew the Kilrathi race together in common cause. Their homeworld was visited by a race of peaceful interstellar explorers. The kilrathi obtained the spacegoing technology of their visitors -- first through guile, then by force -- then went forth and conquered the aliens' home world and colonies. At that point the Kilrathi, like humanity a bit further up the Orion arm of the galaxy, began to expand aggressively into space. Contact was only a matter of time.
The Kilrathi were first encountered by the Terran Confederation scout ship lason in 2629. About 20 minutes after contact, and without previous communication, a Kilrathi ship destroyed the lason. For the next four years the Kilrathi refused -- violently -- all offers of trade (other than the occasional ransom) or diplomacy, while steadily expanding their piratical operations into Confed Space. In 2634, after the unprovoked destruction of an unarmed transport filled with children, Confed formally declared war on Kilrah. The War was to last for 35 years, claiming the lives of 2.1 trillion humans and 7.4 trillion Kilrathi.
The first five years of the war were perhaps the most hellish, with the Kilrathi unleashing massive blitzkriegs of suicide fighters at Confed fleets, and indiscriminately employing weapons of mass destruction against civilian targets. Strategically, the first five years centered around the struggle for the Kilrathi-occupied world of McAuliffe, which was finally retaken by Confed in 2639, in a massive strategic ambush engineered by Captain Geoffrey Tolwyn