I believe this was part of the background for an RPG I might have played briefly once, more than 20 years ago.
The bit that stayed with me is the alien race, whose average intelligence is normally not as much as normal human intelligence. When they first met humanity they were a bit afraid of us, because we were smarter, but the first time humanity and this race fought humanity discovered that being in combat made them much smarter. I believe they actually had genius-level intelligence for as long as they were in mortal danger. As a result, they innovated very quickly in battle and rapidly became dangerous opponents.
One result of this is that after a battle they would have some new weapons or devices that they would build, but they wouldn't necessarily know how to use them properly until the next time they were in combat. The one case that sticks in my mind is this race's main tank, that was originally (for some reason) built with the turret facing backward from its normal driving direction, so that's how it's still being built. I definitely recall a black-and-white sketch of the tank and its crew.
It's also vaguely possible this was an illustrated book packaged with a computer game, back when that was still a thing. It's also possible this was one of those "make up little stories to go with the art" books that were popular in the 1980s and I'm way off on the time.