In "The Daleks" (1963–64), the Thals describe themselves as a warrior race who fought a terrible neutronic war against the peaceful Dals, with whom they shared the planet Skaro. Radiation from the war caused both species to mutate. In the case of the Thals the mutation came full-circle, returning them to their original appearance of blond humanoids. They have renounced violence and become pacifist farmers. During the story it is revealed that the Dals, now calling themselves 'Daleks', have evolved into aggressive creatures who cannot survive outside of the mobile, metal casings they have created. After centuries of freedom from strife the Thals are forced to take up arms again when the Daleks attempt to wipe them out by releasing radiation into Skaro's atmosphere. The First Doctor helps the Thals to victory, with all of the Daleks apparently dying when the flow of static electricity required to power their casings is disrupted.