The Huffington Post has published a cultural history, by Kevin Lankes, of Godzilla's atomic origins. The original Japanese film came out in 1954, shortly after the U.S. military's "Operation Castle Bravo" H-bomb "test" at Bikini blanketed a Japanese fishing fleet with radioactivity, contaminating its catch (some of which was then sold and consumed across Japan to unwitting families), and killing one of the crew members of the fishing boat Lucky Dragon 5 within a matter of months (more Lucky Dragon 5 crew died later from their radiation exposures).
The article quotes Charlotte Eubanks, Assistant Professor of Comparative Literature and Japanese at The Pennsylvania State University, on the widespread cultural anxiety at the time of the film's release:
"During the U.S.-led occupation, which lasted until 1952, there was a moratorium on any press coverage dealing with the atomic aftermath in any in-depth way. The thinking was that too much attention to the atomic bombings would derail democratization efforts and would undermine U.S. authority, particularly since the U.S. had already begun using Japanese territory as a base from which to launch bombing raids on Vietnam. With the end of the occupation, some activists and journalists started to deal directly with the atomic bombings, but they were not getting much traction. People were more interested in trying to rebuild. But then there was a real game-changer. The U.S. conducted a nuclear test over the Bikini atoll and a Japanese fishing ship, the Lucky Dragon, its crew, and all their fish were exposed to the fallout radiation. When this hit the newspapers, it ignited an enormous scare, as people throughout the country feared that they had been exposed to nuclear radiation through consuming tainted fish. That was in March 1954, shortly before the release of Gojira, the opening scene of which features a fishing crew exposed to an unexplained, destructive flash of light. So, when that hit the big screens, it touched a real nerve with the Japanese public."
A new Hollywood version of Godzilla will hit theaters on May 16th. In a Daily Beast interview, the director admits that the Fukushima nuclear catastrophe has influenced the film.