Great War (The Evil of the Daleks)

The Great War was, according to some accounts, the name used by the Daleks to identify a series of galactic conflicts fought after 4000 which nearly resulted in the extinction of the Dalek race.

Origin
The Great War's origin could be traced back to the Daleks' alliance with Mavic Chen and the rulers of the Outer Galaxies, and their attempt to destroy the Solar System with the Time Destructor. Due to the interference of the First Doctor, the Time Destructor's Taranium core was stolen, leading the Daleks and Chen to chase the Doctor through time until they recovered it, after which the Daleks broke off the alliance. The Doctor, Steven Taylor and Sara Kingdom followed them back to Kembel and freed the surviving delegates who fled back home to warn their civilisations and others of the Dalek attack. The Doctor managed to get hold of the Time Destructor and activated it, wiping out the invasion force stationed on Kembel. The Dalek Prime was left to deal with the failure as the fleet and the Black Dalek lost on Kembel were near irreplaceable. (TV: The Daleks' Master Plan, PROSE: Mission to the Unknown/The Mutation of Time)

The wars
After the Daleks' failure, their plans were exposed and several powers retaliated by declared war on the Dalek Empire over the course of the following millennium. Much of the known events that occurred during these years were massive Dalek defeats as they were driven back on all fronts: During this time, the Dalek Prime became the Dalek Emperor. (PROSE: The Evil of the Daleks)
 * A Thal offensive in Sector Seven resulted in the loss of 200 Dalek saucers.
 * The Draconians annihilated half of the Dalek fleet along the Draconian frontier.
 * The efforts of the Terran Federation saw six worlds liberated from Dalek rule.

End of the wars
Over 1000 years after defeat on Kembel, Dalek computers predicted that the wars would eradicate the Dalek race in as little as 80 years if the defeats continued. The Dalek Emperor ordered the Daleks to conduct research into the Dalek Factor in a last ditch effort to prevent this. The Second Doctor intervened and infected many of the Daleks with the Human Factor and they began to question orders which escalated into a full-scale rebellion. The Emperor Dalek's guards retaliated and the ensuing battle destroyed the Dalek City, seemingly taking the Dalek race with it and ending the wars. (TV: The Evil of the Daleks, PROSE: The Evil of the Daleks)

Behind the Scenes
The only reference to the Great War is in the prologue to the novelisation of The Evil of the Daleks by John Peel, although the connections to the other stories references in the article are made clear.