In the 1930s and 1940s, three film serials were made based on the Flash Gordon comic strip. They starred Buster Crabbe as Flash Gordon, Charles Middleton as Ming the Merciless, Jean Rogers as Dale Arden, and Frank Shannon as Dr Hans Zarkov.
The three serials were:
- Flash Gordon (1936)
- Flash Gordon's Trip to Mars (1938)
- Flash Gordon Conquers the Universe (1940)
The serials were syndicated on US television during the 1950s, under the title Space Soldiers to distinguish them from the 1954 Flash Gordon TV series starring Steve Holland.
The 1930s film serials provide examples of:
- Adaptation Dye-Job: Dale is brunette in the comic strip but was made blonde in the first serial — even though this meant bleaching brunette Jean Rogers' hair — because of the power of the Hair of Gold, Heart of Gold trope.
- Bald of Evil: Emperor Ming.
- Bears Are Bad News: Vultan's pet Urso.
- Cat Fight: Aura and just about every other female character at some point.
- Clothing Damage: Certainly close to an Ur-Example for Sci-Fi. It happens in the very first installment to Flash, leading to him Dressing as the Enemy.
- Defeat Means Friendship: Thun the Lionman joins forces this way.
- Deflector Shields: The "Resistoforce" on Barin's ship (in 1936!).
- Detective Mole: Ming tasks his High Priest of Tao with uncovering a traitor who provided Flash information. The Priest is the one who did so.
- Dramatic Unmask: Ming's masked champion swordsman is revealed to be Prince Barin.
- Dressing as the Enemy: Flash.
- Electric Torture: Used as a cliffhanger in the first serial.
- Eviler Than Thou: Ming proves to be this for Azura; he backstabs her once he gains possession of her magic sapphire.
- Go-Go Enslavement for Dale... and Zarkov.
- Hair of Gold, Heart of Gold: Dale, in the first serial.
- Love Potion: Ming tries one on Dale.
- Nice Job Breaking It, Hero!: Flash single-handedly decimates a Lionman fleet... that was en route to assault Ming.
- Non-Indicative Name: Flash Gordon Conquers the Universe. The final installment features a tortured rationalization of the title that does not involve any actual universe-conquering.
- Opening Scroll: Only the third serial, Flash Gordon Conquers the Universe, utilized this (and it wasn't the first, as Universal had used this recap method in its serials starting in 1939). The first serial used non-scrolling text to recap the previous chapter, and the second utilized comic book-type art for its recaps.
- People in Rubber Suits: Almost twenty years before Godzilla.
- Public Domain Soundtrack: Besides music cribbed from various previous Hollywood films, the score includes pieces by Johannes Brahms, Fryderyk Chopin, Edward Elgar, Franz Liszt, Pyotr Ilyich Tchaikovsky, and Richard Wagner.
- Shark Pool: A cliffhanger in the first serial involves Flash trapped in a tank with a giant octopus.
- Slurpasaur: The first of Mongo's denizens Flash faces.
- Speak Now or Forever Hold Your Peace: Flash and Thun crash Ming's wedding to Dale before the gong is sounded the requisite 13 times. Which amounts to the same thing.
- Stock Footage: Scenes of the destruction wreaked upon Earth by Ming and the resulting pancking crowds were stock footage from newsreels. Conquers the Universe used footage from the 1930 film The White Hell of Pitz Palu for establishing shots of the frozen wastes of Frigia. The second and third serials also made increasing use of recycled footage from earlier in the series.
- Syndication Title: In the 1950s the serials were syndicated on TV under the title Space Soldiers (there being an actual made-for-TV Flash Gordon series also airing at the time).
- Trap-Door Fail: Inverted, as the door works fine on Flash, only Ming's daughter is inadvertently dropped, too.
- We Will Use Manual Labor in the Future: Ming the Merciless has many slave laborers on Mongo.