Cyber-invasion (The Moonbase)

On 15 October 2070, the CyberTelosians attempted to invade the planet Earth using the Moonbase. (PROSE: Doctor Who and the Cybermen, TV: The Moonbase, AUDIO: The Early Cybermen)

Origin
According to one account, the Cybermen who attacked the Moonbase identified themselves as descendants of the first space travellers from Mondas, (PROSE: Doctor Who and the Cybermen) the humanoid Mondasians having converted themselves into CyberMondasians. (AUDIO: Spare Parts) These space travellers had left before Mondas was destroyed during the Mondasians' invasion of Earth in 1986. (PROSE: Doctor Who and the Cybermen) According to yet other accounts, the space travellers had only come to Telos as a direct result of Mondas' destruction. All but wiping out the native Cryons, a humanoid species distinct from humans, the Telosian Cybermen used their refrigerated cities as repositories of their number cryonically frozen in suspended animation. (TV: Attack of the Cybermen, PROSE: Attack of the Cybermen)

It was a matter of some dispute whether the 2070 attack on the Moonbase preceded or followed the Cyberman attack on Space Station W3, also known as the Wheel. (TV: The Wheel in Space) By one account, the attack on the Wheel occurred four years later, in 2074. (PROSE: The Cyber Files) According to Hegelia's CyberHive chronology, the attack on the Wheel occurred some four decades before the 2070 attack, the Wheel having been attacked by the "late CyberFaction" which remained in Earth's solar system before advancing to a new form which, after failing to seize the Moonbase, colonised Telos and became recognised as the Telosian Cyber-subspecies. (AUDIO: The Early Cybermen)

Invasion
The Telosian Cybermen attempted to destroy the Earth in order to eliminate humanity, whom they saw as a potential threat to the Cyberman Empire, as well as gaining retribution for the destruction of Mondas. However, this attack was thwarted by the Second Doctor. (PROSE: Doctor Who and the Cybermen, TV: The Moonbase)

Aftermath
According to the CyberHive history, compiled from the Cyber-Documents according to the judgment of ArcHivist Hegelia, the Cybermen did not infact seize Telos and subjugate the Cryons until after their attack on the Moonbase. Considered descendants of the early CyberFaction which left Mondas for Planet 14, these Cybermen were formally recognised as CyberTelosians by Hegelia. (AUDIO: The Cyber Nomads)

Alternate timeline
In an alternate timeline where Cybermen from the end of the universe allied with and began rewriting history, (COMIC: Supremacy of the Cybermen) the Second Doctor was partially converted while on the Moonbase, (COMIC: Prologue: The Second Doctor) pledging his allegiance to the invading Cybermen. This timeline was reversed when the Twelfth Doctor and Rassilon regenerated the universe. (COMIC: Supremacy of the Cybermen)

Behind the scenes

 * The Discontinuity Guide places the attack on the Wheel as following the 2070 Moonbase attack but no later than the early 22nd century.