Thal evacuation of Skaro

Following the Thal-Dalek battle, a Dalek attack forced the Thals to evacuate their home planet of Skaro. (PROSE: The History of the Daleks)

Background
When the Dalek City was seized by the Thals, Alydon discovered that they could use a great deal of the Dalek technology for their own purposes. Especially useful were the hydroponic gardens which enabled the Thals to feed themselves. With the First Doctor and his companions leaving in the TARDIS, the Thals were left to peacefully take over the Dalek City and adapt its technology to their own uses. In the aftermath, the Thals prospered and grew. The surface radiation died down in almost all areas, and eventually the Thals began to plant in the soil of Skaro. In the city the Thals made great strides studying the technology of the Daleks. From it they built and flew their first spacecraft, and were actively looking into the possibility of inhabiting other planet. As the Doctor and his friends were recorded in their history, they knew there was life elsewhere, waiting to be found. By that point, various exploratory parties had mapped out the planet but all had avoided the two old bunkers from the Thousand Year War, not wishing to approach them as they were identified as reminders of the long-finished conflict. (PROSE: The History of the Daleks)