Cyber Wars of the 250th Millennium

The Cyber Wars of the 250th Millennium (PROSE: The Secret Lives of Monsters) were a series of Cyber-Wars fought primarily between the Cyber Legions and humanity. During the Cyber Wars, the Cybermen devastated the Tiberian Spiral galaxy (PROSE: Ghost in the Machine, A Girl Called Doubt) and used it as their "hibernation galaxy". (PROSE: The Mondas Touch) Although humanity won the Wars through the Tiberian Spiral galaxy's total destruction, at the cost of "a million million lives", remnants of the Cyber Legions survived. (PROSE: The Mondas Touch, TV: Nightmare in Silver)

Origins
The Cyber Wars of the 250th Millennium began when the Cyber Legions formed, speculated by one source to be the result of cross-pollination between the Cybermen of two separate universes. (PROSE: The Whoniverse) The first were the Cybermen of N-Space itself, who had fought humanity on countless prior occasions, (TV: The Tenth Planet et al.) including numerous previous Cyber-Wars, (TV: Revenge of the Cybermen, Earthshock et al.) The second were the Cybermen of Cybus Industries, (TV: Rise of the Cybermen, The Age of Steel) who, after failing to conquer their universe's Earth, and then the Earth of N-Space, (TV: Army of Ghosts, Doomsday) were scattered across N-Space, (TV: Cyberwoman, PROSE: Made of Steel, COMIC: The Power of the Cybermen) the Void, (TV: Doomsday, The Next Doctor) and at least one other parallel universe. (COMIC: The Girl Who Loved Doctor Who)