In early 1954, Toho producer Tomoyuki Tanaka set into motion plans to make a movie derived from various popular sources at the time, including the then-recent American movie THE BEAST FROM 20,000 FATHOMS. Along with Eiji Tsuburaya, he put together a concept of a monster movie involving a giant octopus that would terrorize Japan, culminating in the monster attacking a ship.

Screenwriter Takeo Murata altered the concept greatly, replacing much of the story, as well as the main monster. Gone was a gigantic octopus, and in his place was a prehistoric reptile reborn from atomic energy: Godzilla.