"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. We took the technology they left behind, and rapidly built ourselves into a starfaring civilization. Because we haven't got a moment to lose. Because it's clear that there are even more powerful, more hostile aliens out there, and Earth needs...