In 2526, an interstellar conference was conducted on Earth to assembling the military forces of many powerful planets against them.[statement unclear] Led by the Cyber-Leader, the Neomorph Cybermen attempted to prevent this conference by destroying the Earth, only to be thwarted by the Fifth Doctor. (TV: Earthshock)
ArcHivist Hegelia suggested that an agreement was reached to join forces against the Cybermen, resulting in a Cyber-War beginning in the solar system with a battle between the main Cyber-Fleet and human forces which extended to other parts of the galaxy before the Cybermen were ultimately overcome. From the document Departure from Telos, Hegelia found an account of the Cybermen's attempt to leave Telos, which the ArcHivist believed was in anticipation of a significant attack on the planet by galactic forces. (AUDIO: The Ultimate Cybermen) This attempt ended in failure as Telos' Cyber-Control was destroyed along with seemingly all Cybermen on the planet. (TV: Attack of the Cybermen, AUDIO: The Ultimate Cybermen)