One of the most popular tropes, especially in science-fiction, is that of the superweapon: the huge, iconic invention that will turn the tide of battle and ensure the ultimate victory of the side that wields it. The most easily-recognized of these weapons is, of course, the Death Star, the planet-killer with the Achilles’ heel exploitable by the scrappy fighters the Rebels had. But why is it that historically, superweapons tend to work, not just as badly as the Death Star, but even worse? After all, the Death Star vaporized a planet.  Historically, experimental supposed-to-be war-winning weapons don’t usually get even that close to success. Why not?

Because The Wrong Side Has Them

Historically, superweapons are not developed by the equivalents of the Empire. Superweapons are developed by the Rebel Alliance. In other words, they are developed by the side that has the smaller army, the smaller economy, and that is in the most desperate straits. And the reason for this is easy to see: because the stronger side is already winning with the weapons they have! It was the Confederates that produced ironclads and submarines, not the Union with its overwhelming Navy. It was Nazi Germany that produced jet fighters and V-2 rockets in the late days of the war, not the Allies with their overwhelming air superiority. It’s only when you’re losing that you need a game-changing weapon to turn the tide of battle. The only exception to this rule is the atomic bomb, which is not actually an exception (see below).

Because They Tend to Come With A Whole Lot Of Suck

Superweapons are pretty much by definition untested systems, for reasons discussed  above: the side that needs them needs them right away, and they don’t have time for refining the technology. Just to give a few examples, the first submarine ever to sink an enemy ship in wartime, the CSS Hunley, went down with its target. This was predictable, as she had already killed two crews in training. Hunley was very good at the “submerging” part of “submarine,” and not so good at the “surfacing” part. The Nazi jet fighters performed excellently, but had ridiculously short ranges because of fuel inefficiency. Similarly, their V-2 rockets were a triumph of cutting-edge technology, and the Germans desperately needed artillery that could strike hundreds of miles away, but since they had no guidance systems beyond Doing Trig Very Well, this meant that they couldn’t hit anything smaller and more mobile than say, a city.

Because They Attract Attention

On the rare occasions when superweapons do work the way they are supposed to, they do tend to get dogpiled on by the stronger side that they are almost inevitably facing (see above). The Bismarck is an excellent example of this. Built with all the latest technology, the Germans decided to use her as a superweapon that would be tough enough to destroy entire convoys and fast enough to run from the British Navy.

She lasted nine days.

They were a very impressive nine days, and began with the utter annihilation of the battlecruiser Hood and the damaging of the battleship Prince Of Wales, but the result of the effort was that Bismarck attracted the attention of about five battleships and two aircraft carriers, along with many heavy cruisers. After air attacks damaged Bismarck’s rudder, this force pounded Bismarck to scrap. Lest we think this was mere coincidence, the Bismarck’s sister ship, Tirpitz met a similar fate, being used in only one offensive operation over her entire career, and subject to something like 26 Allied operations mounted specifically to get rid of her, which they eventually did.

Because They Are Easily Reproducible

Generally, the better the superweapon is, the more it has been tested. And the more it has been tested, the better it is understood. And the better it is understood, the more easily it can be copied. This is what happened with the Confederate ironclads. With the bulk of the Navy remaining loyal to the Union, the Confederates needed to break the Union blockade of their ports. And since ironclads were being built in Europe, first by France (significantly, the weaker naval power) and soon afterward by Britain (the stronger), their incentive to build ironclads was high, and the technology was becoming known.
Of course, the Union also knew this, and having discovered that the Confederates were building ironclads, quickly did the same. The first battle between ironclads saw the Union rushing its own ironclad to the battlefield only a day after the Confederate fielded the CSS Virginia. Despite the fact that the Virginia had faced three Union warships the previous day and had destroyed two while taking only minor damage to itself (a successful superweapon if anything was), the Monitor proved a match for it.
And that was the beginning of the end. Because the Confederacy was the poorer and less-industrialized of the combatants, they managed to produce only 30 ironclad vessels during the war in total, while the Union turned out about 50 ships of the Monitor class alone. If a superweapon really works, it won’t work fast enough to stop the stronger side from building more of them faster.

If Matching Them Doesn’t Work, Countermeasures Often Do

One of the most successful “superweapons,” pioneered by Germany, has been the torpedo-armed submarine. It was created to destroy the British Navy, and had many advantages that scared the pants off naval planners at the time: The submarine could travel invisibly. The submarine’s torpedoes attacked below the waterline, potentially killing a battleship in one shot. The submarine could scatter and hunt merchant ships in the ocean, killing them at will. The submarine could pass underneath blockades, rendering them ineffective.

In some ways, this appeared to be the perfect superweapon, especially because it didn’t matter whether the British matched it! What would it do with its subs? Guard the convoys? Submarines in the World Wars couldn’t hit each other with dumb-fire torpedoes except by sheer luck. Kill German merchant ships or naval vessels? The British Navy could already do that!

Well, it turned out that the British (and Americans) could do a number of things that weren’t terribly complicated. They could develop long-range patrol aircraft that could hunt and track the subs when they inevitably had to surface for air. They could create armored belts below the waterline for their ships, and anti-torpedo screens that could make the torpedoes detonate prematurely. Faster and stronger destroyers could guard the convoys and use cannon and depth-charges to sink the subs. As it turned out, subs could only effectively threaten surface warships (which were all bigger and more heavily armed and armored) when they managed to line up a shot unseen, and the torpedoes themselves tended to suffer from copious amounts of the aforementioned suck.

But Wait! What About The Atomic Bomb? Doesn’t That Disprove All Your Points?

Not at all. In fact, it reinforces them. First of all, the United States and the Allies were not yet fighting the war when Albert Einstein sent his famous letter to FDR, recommending its development. They were losing it when the Manhattan Project began. Most importantly, it was triggered by the belief that Germany, the weaker side in the wider war, was already researching them. By the time the bombs were actually built, of course, things had changed, and they were no longer necessary to win the war. To shorten it, yes, but that’s a different thing. And it attracted enough attention for the Soviets to place spies in the Manhattan Project, which they reproduced in only four years. Finally, the atomic bombs, contrary to appearances, really did contain a lot of suck. They poisoned the battlespace with fallout, and the bombers then necessary to carry them were vulnerable to interception. As a deterrent to large-scale war, the atomic bomb is a wonderful weapon. As an actually usable weapon system, it is not.

And that’s why, although superweapons are an awesome ingredient in fiction, they really don’t show up in history very often.