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, which would be used to establish colonies on other planets. 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)

The Evacuation
Led by the Dalek Prime, the Daleks who had been trapped since the end of the Thousand Year War had perfected underground mining systems, which automatically delved for the metals that their automated production lines needed. Left alone with the vast embryo banks, the Daleks built up their numbers and honed their warfare techniques, studying the computer records that had been entombed with them. Filled with a hatred for all other life forms, the Daleks emerged to invade Skaro, bringing death to the bewildered Thals after five hundred years of peace. This attack was led by the Dalek Prime's warlord, the Black Dalek, reducing Skaro to a burning cinder in a matter of hours.

With the initial attack, the Thal starships still close to the world returned. There, they collected what survivors they could find, and whatever could be salvaged before the Daleks destroyed their society. They then fled for space, leaving the Daleks as the masters of Skaro. After all the Thals' efforts, Skaro was was uninhabitable again. The overcrowded evacuation fleet staggered across space to one of the colony worlds that the Thals had been experimenting with. Now they had no option but to trust the planet for their survival. With the arrival of the ragged fleet, the Thals vowed that never again would the Daleks take them by surprise. Putting aside their stance of pacifism, the Thals determined that they would somehow, someday, utterly destroy the Daleks. (PROSE: The History of the Daleks)

Aftermath
Back on Skaro, the Daleks remained unaware of the Thals' change in mentality, that those who escaped would soon die out or be ultimately destroyed. For at least a hundred years, the Daleks prospered, rebuilding their capital and eliminating all trace of the Thals rebuilt. The city grew as they raided their old bunker for equipment, computer systems, and metals. Finally, the remnants were buried, as the Daleks sought to cover the fact that they had been forced to spend 500 years lurking below ground while the Thals had prospered. As the capital expanded, the Daleks gained access to the accumulated knowledge of the Thals in the computers they discovered. From the Thals' computers, the Dalek Prime found out about starflight; since the Thals had no warning of the Daleks' attack, all of their plans and propulsion methods were laid out in detail in their records. The Daleks had already been experimenting with anti-gravity, building discs that could contain a single Dalek and support it in the air, controlled mentally by the Dalek creature. Utilising these principles with the Thal knowledge, the Daleks pieced together a hybrid starship. This was tested, proven successful, and then used as a basis for the Dalek Fleet. Despite the fact that Dalek embryos were produced through cloning, the Dalek numbers still remained fairly small. Worn out from the wars, Skaro was almost exhausted, and contained too little metal for the Daleks' purposes, leading them to look for another planet to mine, one with terrain to accomdate the Daleks, plenty of metallic ores, and preferably abundant radioactive elements that could be taken fairly simply. It had to be a world in which they could move about. Any native species would be used then destroyed. The Thal deep-space telescopes, which were still in orbit above Skaro, were used by the Daleks to identify their ideal planet: Earth. Earth would be successfully conquered by the Daleks in the mid-22nd century, only for it to be liberated eventually through the intervention of the First Doctor. In its aftermath, the Daleks looked to their neighbouring star systems but neglected their homeworld, which would be seized by the Thals. (PROSE: The History of the Daleks)

The Doctor was aware of the Thal evacuation of Skaro, having spoken of it to Sam Jones in his eighth incarnation. (PROSE: War of the Daleks)

Behind the scenes

 * The Terrestrial Index stated that the Thals were "exiled" from Skaro before eventually "reconquer[ing]" the planet during the Second Dalek War in the 25th century, forcing the Daleks to adopt a replacement homeworld. Ultimately, following the Third Dalek War, the Daleks launched a new attack on Skaro, before the end of the 26th century, in which they exterminated most of the Thals, leaving the planet a bombed-out ruin which would be not be of use to the Daleks until the Movellan Incident.