Karl Frantor (Earthman) and Antil (Venusian) are visiting Ash-taz-zor, a city built by ancient Venusians several thousands of years ago. While wandering the alcoves of ancient advanced technology and art, they discover a secret room that hides five cylinders and a complete document in the ancient Venusian ceremonial language. Karl wanders off for awhile, and when he comes back, Antil is frozen in fear. Karl shakes Antil awake, and he immediately insists to the Earthman that they must make great haste back to the domed city of Aphrodopolis. Once there, Antil gives Karl an ominous warning to persuade Earth to moderate its racism against the Venusians, or else Antil will be forced to destroy the Earth.
Five years later, the Venusians revolt against the domed cities of Earthmen. Many cities are overtaken in a short timeframe, and the Little Green Men successfully take back half of their world in a matter of hours. Karl Frantor, son of the Minister of Education, pleads with the inner council of the Terrestrial Government. They decide to send him as an envoy, under the protection of Admiral von Blumdorff and his armada. Under these conditions Antil and Karl meet again. Antil explains the artifacts were a Lost Superweapon, dreadful weapons, and that they can use these weapons to attack Earth from the surface of Venus. He pleads with Karl to convince the Terrestrial Government to treat Venus as their equal so that the weapon will not be used. Karl believes him, but the Admiral is angry with his gullibility and orders an attack.
"The Weapon Too Dreadful to Use" was published five more times; The Future Makers (1968), Science Fiction Special 5 (1971), The Early Asimov (1972), Urania (issue #625, August 1973), and Sirius (issue #3, September 1976).
"The Weapon Too Dreadful to Use" provides examples of:
- Advanced Ancient Humans: In this case, it's the ancient Venusians who had a culture that was incredibly advanced both artistically and technologically. Karl Frantor, an Earthman, tries to convince his Venusian friend Antil that sharing the incredible achievements would make the people of Earth more willing to treat the people of Venus as equals, instead of like dirt.
- Advanced Ancient Acropolis: Ash-taz-zor was built by Venusians, back when their technology and cultural interests were highly advanced. Artifacts of great power and unknown by humans are shown to Karl Frantor. While wandering the halls and alcoves, he points out a secret room to his friend Antil, and they discover a Lost Superweapon, the titular dreadful weapon.
- And I Must Scream: The titular weapon is dreadful because it separates the mind's ability to reason from the body's autonomic functions. It is believed that the mind is still intact, but unable to control the body, making it a prisoner from within a vegetable. The person could starve or dehydrate to death while food and water was right in front of it because the mind is unable to make the simplest commands.
- Classical Tongue: Antil (a Venusian with a strong interest in history) is excited to find a complete document in the ancient ceremonial language of Venus because previous documents have all been disjointed fragments. It is normally a dead language, but Antil is familiar with the system of writing where two, and sometimes three, coloured dots form words.
- Domed Hometown: Humans have colonized Venus with domed cities like Aphrodopolis to keep out the heavy rains.
- Exactly What It Says on the Tin: Completely subverted, as the Weapon Too Dreadful To Use was in fact used.
- Fantastic Racism: For fifty years Earthmen have been colonizing Venus. The native sentients were initially greeted with peace and promises of trade. Since then, however, the Venusians have been kept from voting on the Venusian Provincial Congress, prevented from sharing stratocars, restaurants, and houses. Colleges and land are withheld from them. One of the characters draws a comparison between the Venusians and the Red Indians.Antil: "Are we allowed to vote? Have we any representation at all in the Venusian Provincial Congress? Aren't there laws against Venusians riding in the same stratocars as Earthlings, or eating in the same hotel, or living in the same house? Are not all colleges closed to us? Aren't the best and most fertile parts of the planet pre-empted by Earthlings? Are there any rights at all that Terrestrials allow us upon our own planet?"
Karl Frantor: "What you say is perfectly true, and I deplore it. But similar conditions once existed on Earth with regard to certain so-called 'inferior races,' and in time, all those disabilities were removed until today total equality reigns. Remember, too, that the intelligent people of Earth are on your side. Have I, for instance, ever displayed any prejudice against a Venusian?"
Antil: "No, Karl, you know you haven't. But how many intelligent men are there? On Earth, it took long and weary millennia, filled with war and suffering, before equality was established. What if Venus refuses to wait those millennia?"
- Featureless Plane of Disembodied Dialogue: The terrain of Venus is described as having monotonous white-and-grey clouds, reddish-brown vegetation, and an eternity of rain. However the rooms are never given more than a cursory description, and the only person to be described in any detail is Antil, who represents the native Venusian sapients.
- Fictional Colour: The native of Venus have much, much greater colour perception than humans. This becomes a plot point, as it means no humans can read their ancient languages without a spectrograph. Particularly the operating manual for the Forgotten Superweapon mentioned in the title.
- Finale Title Drop: The last paragraph describes the peace treaty between Earth and Venus, and the destruction of the five titular guns.And with the signing of the treaty, a whirling speck shot out toward the sun. It was—the weapon too dreadful to use.
- General Ripper: Admiral von Blumdorff is a straightforward military man, in control of an entire armada and followed the philosophy of brute force as the one true military strategy. Proud and blustering, when he hears the report of the dreadful weapon, he dismisses it as a bluff and orders an immediate attack on the planet.
- Humanity Is Advanced: 20 Minutes into the Future, Earth has built ships and a navy to explore space and colonize Venus. The native Venusians are of a much lower tech level, and for fifty years they're treated as a subhuman intelligent race. This doesn't change until the Venusians discover a Lost Superweapon capable of defeating an attacking navy.
- Humans by Any Other Name: People from Earth are called Terrans, Terrestrials, or Earthmen.
- I Love Nuclear Power: The lamps that Karl Frantor and Antil use while exploring Ash-taz-zor, ancient VEnusian ruins, are called Atomite lamps. Antil takes pleasure in pointing out an artifact which was an atomic energy converter much more efficient in design than contemporary Terrestrial devices.
- Little Green Men: Antil, who represents the people of Venus in this story, is small and thin, with green skin and rounded cheeks, as well as large colourful eyes. Due to the differences between humans and Venusians, the humans hold the aliens in contempt, dominating life on Venus.
- Lost Superweapon: While exploring Ash-taz-zor, a city built by ancient Venusians several thousands of years ago, Antil and Karl discover a secret room with five cylinders and a scroll in the ancient ceremonial language of Venus, which provides instructions for the use of the five guns. At first, Antil doesn't explain what these weapons can do, but many years later, when the Venusians attempt to reclaim their planet from Terran rule, he does, with the threat that they will turn these weapons on Earth itself if they do not cede peacefully and begin treating the Venusian race as equals.
- The Namesake: The title refers to a weapon that divorces the ability to think and reason from autonomic functions, such as swallowing, heart beats, and breathing. Antil, the one who rediscovered the weapon in a ruin several thousand years old, believes that rather than just lobotomizing a person, the mind is still intact, but unable to control the body.
- One World Order: The Terrestrial Government runs all of Earth's affairs, with a President of Earth. Until the native Venusians revolted, there was a provincial Venusian Government as well, which reported to the Terrestrial one.
- Sacred Language: Antil (a Venusian with a strong interest in history) is excited to find a complete document in the ancient ceremonial language of Venus because previous documents have all been disjointed fragments. It is normally a dead language, but Antil is familiar with the system of writing where two, and sometimes three, coloured dots form words.
- Venus Is Wet: Covered in brown-grey clouds and perpetually raining, Earthmen build domed cities to keep out the wetness (and the Venusians).