The problem with Xenobiology and Xenopsychiatry is that Alians are, well, Alien.
So when the predominantly peaceful and staid Hegemony discovers a planet of sentient but murderously militant omnivores, they dispatch their nastiest clients (the carnivorous pack hunting Shongairi) to force the Humans to submit.
The Shonagiri, finding that Humanity has progressed much faster than expected in the intervening centuries between initial survey and the arrival of their colonization fleet, decides to initiate their colonization efforts with a global decapitation strike of KEWs (Kinetic Energy Weapons, i.e. rocks dropped from orbit). The survivors, they are sure, will thereafter submit.
What could go wrong?
A fun read with some interesting twists.
I heard David Weber tell the denouement of this story in my Library in March of 2009 as we hosted him for food, drink, and talk after a book signing here in San Jose, and the plot remains true with the addition of minor characters and additional scenes from around the globe.