Weber, David, 1952- Out of the dark series

"We've come a long way in the forty years since the Shongairi attacked Earth, killed half its people, and then were driven away by an alliance of humans with the other sentient bipeds who inhabit our planet. But it also transpires that the Shongairi expedition that nearly destroyed our home planet ... wasn't an official one. That, indeed, its commander may have been acting as an unwitting cats-paw for the Founders, the ancient alliance of very old, very evil aliens who run the Hegemony that dominates our galaxy, and who hold the Shongairi, as they hold most non-Founder species, in not-so-benign contempt."