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The trilogy's protagonist is Colin MacIntyre, who is on a routine training flight over the Moon when it reveals itself to be Dahak, a self-aware space battle planetoid millennia old. MacIntyre and Dahak defeat Dahak's previous enemies and restore a galactic empire.
See also
Moonfall (film), a 2022 American science fiction film about the Moon being a spaceship from a fallen human civilization that seeded the Earth with humanity
An excerpt of Empire from the Ashes is available for download or reading online at the Baen Free Libraryhere. The whole novel can be found here.
On January 8, 2014, David Weber stated on his official forums that there are "two Dahak sequels I have plotted out", although there is no planned release date.