Cyber-Wars

The Cyber-Wars was a galactic conflict in which an alliance made a concerted effort to wipe out the Cybermen.

The wars
The earlier Orion War was implied to have been part of the Cyber-Wars. (WC: Real Time, AUDIO: Real Time)

The conflict began in 2526. (TV: Earthshock) A force of time-travelling Cybermen from the end of the conflict attempted to prevent the war. They tried to destroy the Earth, first with a Cyber-bomb and then by crashing a human freighter into the Earth to prevent the alliance who planned to fight them from forming. Both of these attempts were stopped by the Fifth Doctor. (TV: Earthshock)

It was during the earlier Vogan War that the glittergun was developed. Gold was a major weakness of the Cybermen. The gun could fire gold dust at them. (TV: Revenge of the Cybermen)

In the end, the Cybermen began upgrading themselves to overcome any weaknesses that could be exploited. The Tiberian spiral galaxy was sacrificed to destroy all of the Cybermen with a bomb. (TV: Nightmare in Silver)

Aftermath
The wars resulted in near-complete destruction of the Cyber race. Remnant groups of Cybermen fled across the galaxy. One remnant group attempted to retaliate by destroying Voga, the planet of gold but were destroyed when the Fourth Doctor instructed the Vogans to fire their rocket at the Cyber-ship. (TV: Revenge of the Cybermen)

Some of the deactivated Cybersuits ended up in Webley's collection. However, they had similar appearances to the variety of Cybermen created by Cybus Industries and those of the Cyber Legions. (TV: Nightmare in Silver)

Because of the damage done to one of the planets, Hedgewick bought one cheap and set up his own amusement park there; it was said to be the best ever in all of history. However, unknown to all, some of the badly damaged Cybermen were in stasis below the park and many a patron vanished from it to be used as spare parts so the Cybermen could be rebuilt. 1,000 years after the end of the wars, three million of these Cybermen began to revive but they were beaten when Emperor Ludens Nimrod Kendrick Cord Longstaff XLI set off a bomb to destroy the planet. According to the punishment platoon, if a Cyberman is encountered and can't be quickly destroyed, it is procedure since the end of the Wars to blow up the planet the Cyberman is found on to prevent the return of the species (TV: Nightmare in Silver).

Despite being brought to the edge of extinction by the conflict, the Cybermen gradually recovered. As late as the 52nd century, fleets such as the Twelfth Cyber Legion represented part of a major Cyber power in space. (TV: A Good Man Goes to War)