The "Safehold" book series centers around a group of humans who create a new civilization on a planet called Safehold following an alien invasion of Earth. To prevent the invading aliens from finding them, the human survivors eschew modern industry in favor of a medieval way of life until an android sparks a new era of industrial progress.
The series begins on a ruined Earth following the invasion of the Gbaba, an alien race determined to eradicate humans from the planet. A group of survivors flees to Safehold, an Earth-like planet, where Commander Erik Langhorne brainwashes most of the group into viewing him as an archangel. To maintain his control over the colony, Langhorne then establishes a religion and a church. To avoid detection by the Gbaba, Langhorne avoids the use of technology and runs the colony as a medieval stronghold.
800 years later, a stowaway android, Nimue, awakens on Safehold. Acting as adviser to the colony's current king, Nimue begins to reintroduce various forms of technology. Her actions create strife that results in the crowning of a new ruler and a reformation movement that continues throughout the series.
Set in the distant future, "Safehold" is a science fiction series by David Weber. Tor/Forge published the first book in the "Safehold" series, "Off Armageddon Reef," in January 2007. As of 2015, the series includes eight volumes.