Adiamante Author:L. E. Modesitt Jr. After ten thousand years in exile, the cyber-warriors return in their fleet of spaceships to the planet that rejected them: Earth. — Earth was once the capital of an interstellar empire, but now it's just another inhabited planet in a forgotten universal order. Its citizens survive through kindness, environmental conservation and non-aggressi... more »on. But humanity's great strides toward erasing its violent past are threatened when 12 ships made of indestructible adiamante appear in orbit. The ships are from a former colony bent on subjugating the Earth and its inhabitants. But the strict ethics that have helped revitalize the Earth may be its downfall, as the human homeworld struggles to find a way to save itself without violating its new-found principles.« less
I have beconme a huge fan of L.E.'s Hard Science Ficton. Perhaps it is his underlying themes of the necessity of Liberty and Freedom and the over riding tendency for governments to remove both. This is a must read.