1986 Cyberman invasion of Earth

The Cyberman invasion of Earth was an attempted invasion of Earth by the Mondasian Cybermen in December 1986. (TV: The Tenth Planet) Following the CyberFaction's invasion, this was the second Cyberman invasion of Earth recorded both in the history computer of the CyberFaction (PROSE: Iceberg) and in the Cyber-Documents of Earth, which were compiled into the CyberHive by the ArcHivist Hegelia. (AUDIO: The Early Cybermen)

Origin
"Eons" prior to the invasion, Earth and Mondas were twin planets before Mondas drifted away to the edge of space. (TV: The Tenth Planet)

The invasion
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The Doctor
Shortly following the destruction of Mondas, the exhausted First Doctor began his regeneration. Though he was initially reluctant to change, he was convinced to do so following an encounter with the dying Twelfth Doctor who, unwilling to regenerate himself, was taken back to his own past by the TARDIS. (TV: The Tenth Planet, Twice Upon a Time) Incidentally, the Twelfth Doctor had also been forced to the brink of regeneration by a conflict with the Mondasian Cybermen. (TV: World Enough and Time/The Doctor Falls) Ultimately, the two Doctors parted ways and regenerated into the Second and Thirteenth Doctors respectively. (TV: The Tenth Planet, Twice Upon a Time)

Earth
Professor Allison Williams led the scientific team which investigated the Cyberman ship in Antarctica. (PROSE: The Power of the Daleks) The Cyberships leftover from the invasion were examined and exploited by humans, allowing them to make advances in space travel, leading Sarah Jane Smith to describe the return of Mondas as "both the greatest disaster and most astonishing blessing ever to have happened to the human race." (PROSE: The Power of the Daleks)

The Cybermen
As late as 2070, Earth history books recorded that the Cybermen were all wiped out when Mondas was destroyed. However, there were groups of Cybermen that travelled into space prior to Mondas' destruction. The first settled on the planet Telos. These Telosian Cyberman returned to the solar system on 15 October 2070. Seeking the power used to destroy Mondas, the Cybermen infiltrated the human base on the Moon, when they intended to use to wipe out all life on Earth. They were opposed by the Second Doctor who accused the Cybermen of being motivated by revenge, while the Cybermen claimed that they were acting to eliminate dangers to the Cyberman Empire. Ultimately, their invasion attempt was thwarted by the Doctor. (PROSE: Doctor Who and the Cybermen, TV: The Moonbase)