Some time after the Thousand Year War, the planet Skaro had become a nuclear wasteland. Its principal features were the petrified jungle, in which the Thals lived, and the city of the Daleks. The First Doctor and his companions, Ian, Barbara and Susan, visited Skaro at this time and led some of the Thals to attack the Dalek City. They disabled the power generator and deprived the Daleks of the static electricity they needed to move about the city. (TV: The Daleks) The Third Doctor and Taron identified this period as the First Dalek War. (PROSE: Doctor Who and the Planet of the Daleks) Federation Archivist Ven Kalik used the same name to refer to the Daleks' invasion of Earth and its colonies in the 22nd century. (PROSE: Prelude Deceit)
However, the Daleks survived. Accounts of the first conflict and the part the travellers played in it passed into Thal legend.
Circa 2540, the Daleks had built a base on the planet Spiridon. They planned to launch an army of ten thousand Daleks across the galaxy. They hoped to render the army invisible by study of the native Spiridon humanoids. This plan failed. The Daleks could only remain invisible for a short time.
The Third Doctor helped a taskforce of Thals, who by this time had interstellar spaceflight, to defeat the Daleks, this time using the ice core of the planet to freeze the Dalek army. (TV: Planet of the Daleks)
The Thals fought the Daleks on the planet Terakis and destroyed the planet with a bomb in order to lure half of the Eighth Fleet into a trap which succeeded despite the natives of Terakis killed. (PROSE: War of the Daleks)