The brutal nature of the war between the Kaleds and Thals was inspired by Things to Come (1936). Terry Nation also decided to play up the Nazi allusions which, he now realised, had influenced his original conception of the Daleks.
Mary Whitehouse of the National Viewers and Listeners' Association famously complained to the BBC about this serial, saying it was "teatime brutality for tots...this series has moved from fantasy to real-life violence with cruelty, corpses, poison gas and Nazi-type stormtroopers, not to mention revolting experiments in human genetics".
Katy Manning has said she thinks the Daleks lost their menace beginning with this story because of the introduction of Davros. She said "suddenly it's half a bloke in there... There's nothing human about a Dalek".
Michael Wisher prepared for his masked role of Davros by wearing a paper bag over his head during rehearsals, to help him convey much of the emotion of the part purely through dialogue. Wisher, a heavy smoker, put two holes in the top of the bag so he could smoke underneath it in rehearsals.
Producer Philip Hinchcliffe didn't want to do a story featuring Daleks but inherited this script from outgoing producer Barry Letts. However, Hinchcliffe has since said that this turned out to be a very good story and a successful production that he is proud of.
Philip Hinchcliffe, having been landed with a Dalek story he didn't really want, impressed upon director David Maloney his desire to give it a different feel from previous Dalek stories and make them more compelling than in some of their previous appearances.
When planning stories for season 12, producer Barry Letts and script editor Terrance Dicks felt that it was time for Terry Nation to return to the series and write another Dalek adventure. Letts and Dicks enjoyed the script Nation sent in, but found it too "reminiscent" of many of his previous Dalek stories. The two suggested that Nation instead write an origin story for the Daleks. The stories lined up for the season were handed over to Letts and Dicks' successors, Philip Hinchcliffe and Robert Holmes, with whom it gained a darker tone. Holmes was not a fan of frequent appearances by the Daleks, and only allowed the story because it explored their origins.
In a 2006 interview, Terrance Dicks said that he does not believe the story would have been much different if he and Barry Letts were in charge, though he remarked he would have added some lighter moments to soften the "grim" tone.
The character of Davros was designed by Terry Nation to have created the Daleks in his image, and to also be a "spokesperson" for the Daleks as he felt it was "boring" listening to Daleks giving speeches.
Davros attracted the attention of BBC prosthetics designer John Friedlander who agreed to come off another show to make Davros' mask. The latex mask was moulded to Michael Wisher's face by make-up artist Sylvia James. Wisher could even eat while wearing the mask. Regular latex instead of the more mouldable foam latex was used because the latter was too expensive.