Cyber-Wars

The Cyber-Wars was a galactic conflict in which a united force made a concerted effort to wipe out the Cybermen in 2526. A group of time-travelling Cybermen from the end of the conflict attempted to prevent this. They tried to destroy the Earth, first with a Cyber-bomb and then by crashing a human freighter into the Earth. Both of these attempts were stopped by the Fifth Doctor. (DW: Earthshock)

It was during this conflict that the glittergun was developed. Gold being a major weakness of theirs, the gun could fire gold dust at Cybermen. The wars resulted in near-complete destruction of the Cyber race, with remnant groups of Cybermen fleeing across the galaxy. (DW:Revenge of the Cybermen)

Many planets were destroyed in the war.

Post-War

 * One remnant tried to destroy Voga, the planet that supplied the majority of gold for the Cyber-Wars. (DW:Revenge of the Cybermen)
 * One derelict Star Destroyer ended up in the Garazone System, and was reactivated some fifty years later when the Earth Empire tried to collect Cyber-Technology for use in the Orion War. (BFA: Sword of Orion)
 * One cruiser crashed in the oceans of Earth, and was salvaged by humans, again for use in the Orion War. (BFC: Scorpius)