For anybody who has no idea who the Tevarin are, what's the dime-store version?
TL;DRThe Tevarin were the first alien civilization humanity fought, a warlike race who attacked first, lost two wars, and after their warlord's last stand were absorbed into the UEE, rejecting their old society.
The Tevarin were the first alien civilization that humanity went to war with. They were a very warlike civilization and, according to history, they launched the first attack. Basically we showed up in their system and they attacked us, and it sparked one war, we beat them, and then it sparked a second war. A few years later, one of their Tevarin warlords rose up and organized the remaining Tevarin to try and take back their homeworld, which had been colonized by the humans, and then basically started this long, protracted guerrilla war, which lasted for several years, and then he started to lose. Squadron 42, that's how they first esteemed themselves, in the battle that turned the tide of the war. And then he crashed himself and his fleet into the planet, his homeworld, as a last defiant act. And the remaining Tevarin were assimilated into the UEE and basically wholeheartedly rejected their old society and just stopped caring.
And that's the short version.