The Daleks are one of, if not the most celebrated Doctor Who villain. They have faced every one of the Doctor's incarnations except for the Eighth - the Daleks did, however, have a cameo in the Eighth Doctor's television movie, and their voices were heard.
But the Daleks were not always the metal-encased creatures we see on Doctor Who. In fact, they were once absolutely humanoid...
|Daleks, Susan and the Doctor in the 1963/64 serial "The Daleks" - the Daleks' first television appearance.|
Due to the radiation caused by the weapons used during the war (which may have been one thousand years, or merely a quick neutronic war), both the Kaleds and the Thals mutated very quickly. According to the Thals, they mutated in a kind of full-circle - they went through stages of mutation which eventually brought them back to humanoid form, and made them perfect beings. They became nearly extinct, and became pacifists. The Kaleds, however, mutated in a different matter.
|One of the Thals from the 1963/64 serial "The Daleks"|
During the war, the Kaleds mutated rapidly and irreversibly due to the increasing radiation. Davros thus turned his research from that of weapons and winning the war to the Kaled survival. Davros did experiments on the Kaleds in order to find their final mutated form, and then devised a protective casing. Soon he did not wish merely for survival of the Kaled race, but for utter supremacy - to wipe out all other life on Skaro. Davros continued to manipulate the genetic structure of the mutants, and isolated and removed "weaknesses" such as compassion and morality. These mutations were then housed in a "travel machine", and named Daleks (dalek being an anagram of kaled). These Daleks needed radiation to live, and operated on static electricity. With the help of the Doctor, the Daleks' power source was disabled, and the Daleks were left lifeless in their city.
There would, however, come a time when the power was reactivated, and the Daleks would learn that there were worlds outside of theirs to be exterminated - as they were designed to destroy all life and be loyal only to the Daleks (many were not even loyal to Davros, as he was not a Dalek).
|Davros as seen in his first television appearance in the 1975 serial "Genesis of the Daleks"|
Fun fact: In the 1975 episode "Genesis of the Daleks" the Doctor finds himself on the planet Skaro near the end of the war, attempting to stop the creation of the Daleks. This may have been one of the factors eventually causing the Time War.
Note: There are actually many different accounts of the Dalek's history and creation - certain episodes contradict others, and many details remain unclear. For other accounts, visit here.