The following is excerpted from film historian Charles Lee Jackson II's ebook, The Story of the Making of the Flash Gordon Movie Serials, expanded from his classic Filmfax article.
Casting was mostly easy: the principals returned, though Jean Rogers, who was by then at 20th Century-Fox, was unavailable (She later moved to M-G-M, where she attracted the eye of Louis B. Mayer [sound familiar?], whose advances she rebuffed). Pretty Carol Hughes, an ingénue from RKO and Warners, assumed the part of Dale Arden, and acquitted herself well, looking as much like Dale as Buster did Flash. Society-type player Roland Drew replaced Richard Alexander as Barin, who had slimmed down after settling into married life with Aura, now Shirley Deane. Republic cliffhanger star Lee Powell appeared as back-up hero Roka, and Donald Curtis (later of films such as It Came from Beneath the Sea) was Frigian Captain Ronal. William Royle, about to step into the shoes of Nayland Smith in Drums of Fu Manchu, played a Barin sympathizer in Ming's guard. Stocky Don Rowan was Torch, who had been (as Earl Askem) a mere officer in Flash Gordon, now Ming's trusted Captain. Veterans Byron Foulger, Michael Mark, Ben Taggart, Tom Chatterton, and Herbert Rawlinson, and comparative newcomers like Edgar Edwards and Jeanne Kelly (who was re-christened “Jean Brooks” at RKO Radio – as though someone might confuse her with a certain Metro dancer), as well as favorites Ernie Adams, Ray Mala, and Roy Barcroft in the fairly large cast.
Anne Gwynne, a rising starlet, got the bad-girl role as Lady Sonja. Sonja, carried over from the strip, had been a minor character who had loved Flash, but when rebuffed, allied herself with Ming. She aided the emperor in an escape in exchange for a promise of marriage. He made good his promise – but promptly had the new empress executed. That’s Ming for you. She fared little better on screen, though Gwynne went on to a career in Universal programmers, and still made an attractive star as late as 1958’s Meteor Monster.
Shooting commenced at the end of November 1939, with location work at Red Rock Canyon, the popular shooting location north of Hollywood. Delayed by bad weather, the unit never did quite catch up, even with the prodigious amount of scenes made back at the studio (and even with a second unit added to the picture), and MacRae’s continued efforts to trim the picture’s sequences. The picture closed $8000 over its $165,000 budget.
But the public knew nothing of these trials and tribulations; in fact, they got an added bonus in the "Flash Gordon" daily strip, which began while the serial was playing in theatres.
To see Chapters 11-12 and read more of How the Serial "Flash Gordon Conquers the Universe" Was Made.click here.