The Spoils of War — Alan Dean Foster

The Weave was on the verge of winning a decisive victory after a milennia of war, thanks to their new allies from earth. But then the birdlike Wais scholar Lalelang found evidence that Humans might not adapt well to peace. Researching further, she uncovered a secret group of telepathic Humans called the Core, who were on the verge of starting another war, and then eliminating Lalelang. At the last moment, she was saved by a lone Core commander. He took a chance on her intelligence and compassion, and gambled the fate of Humanity on the possibility that together, they could find an alternative to a galaxy-wide bloodbath....