Weapons That Didn't Pan Out

Pillbox city

Ad Honorem
Jul 2012
Abilene, Texas
I'm talking about weapons or weapon systems that were predicted to have a major impact on the battlefield but failed to meet expectations. I'll throw out one example:

Strategic bombers - Billy Mitchell, Douhet, and other advocates between the World Wars predicted that heavy bombers would render armies and navies obsolete and that bombing cities alone could force countries to surrender. Here we are almost 100 years later and it has almost never happened. I think the only war won by bombing alone was the NATO vs Serbia war in the 1990s.

Are there any other weapons that fell well short of expectations?
Strategic bombers still have the use of taking out major installations that supply a war effort, like factories and trainyards. Although cruise missile spam has somewhat replaced that in the modern age.

I would add the Chrysler TV-8, a nuclear-powered tank, and side-loading machine guns.

Also, chemical weapons being used in combat should also qualify, many sci fi works from the interwar years (like Brave New World) make very heavy mention of poison gas in warfare, only for it to be hardly used after some wars in the 1930s.
Chemical weapons may be great at terrorizing populations, but it's not a very great battlefield weapon.

Tercios Espanoles

Ad Honorem
Mar 2014
Beneath a cold sun, a grey sun, a Heretic sun...
When I started this thread I was thinking that a successful weapon is one that delivers victory to its user or which forces the enemy to change tactics to account for the new weapon. Therefore a failed weapon is one that does not deliver victory nor does it force the enemy to develop new tactics.
By your own definition, I don't see how you can include strategic bombers. They didn't deliver victory in WW2 only because nobody had them in the numbers they deemed necessary to achieve that victory. But they most certainly forced the enemy to develop new weapons and tactics to defend against them. In any event I would argue that, more than any other single contribution, SAC won the cold war.
Oct 2018
The 300 anti-elephant wagons that Rome tried to use against Pyrrhus' 19 war elephants at the Battle of Ascalum (279 BC).

Dionysius of Halicarnassus 20.1.6-7: 'Outside the line (the Roman consuls) stationed the light-armed troops and the waggons, three hundred in number, which they had got ready for the battle against the elephants. These waggons had upright beams on which were mounted movable traverse poles that could be swung round as quick as thought in any direction one might wish, and on the ends of the poles there were either tridents or swordlike spikes or scythes all of iron; or again they had cranes that hurled down heavy grappling-irons. Many of the poles had attached to them and projecting in front of the waggons fire-bearing grapnels wrapped in tow that had been liberally daubed with pitch, which men standing on the waggons were to set afire as soon as they came near the elephants and then rain blows with them upon the trunks and faces of the beasts. Furthermore, standing on the waggons, which were four-wheeled, were many also of the light-armed troops — bowmen, hurlers of stones and slingers who threw iron caltrops; and on the ground beside the waggons there were still more men.'

2.4-5: 'When the king (Pyrrhus) had ordered the elephants to be led up to the part of the line that was in difficulties, the Romans mounted on the pole-bearing waggons, upon learning of the approach of the beasts, drove to meet them. At first they checked the onrush of the beasts, smiting them with their engines and turning the fire-bearing grapnels into their eyes. Then, when the men stationed in their towers (the towers atop the elephants) no longer drove the beasts forward, but hurled their spears down from above, and the light-armed troops (of Pyrrhus, who accompanied the elephants) cut through the wattled screens surrounding the waggons and hamstrung the oxen, the men at the machines, leaping down from their cars, fled for refuge to the nearest infantry and caused great confusion among them.'

View attachment 18684
A (speculative) reconstruction has now been produced by Nicholas Sekunda and Peter Dennis (The Army of Pyrrhus of Epirus: 3rd Century BC, 2019, pp. 32, 47):

Feb 2017
Devon, UK
The Panjandrum in WWII - also known as the Great Panjandrum.

(It has such a good name.)

It was supposed to be able to penetrate the concrete Atlantic walls (10ft high, 7ft thick)...

A description of a day of testing by Brian Johnson for BBC:

"At first all went well. Panjandrum rolled into the sea and began to head for the shore, the Brass Hats watching through binoculars from the top of a pebble ridge [...] Then a clamp gave: first one, then two more rockets broke free: Panjandrum began to lurch ominously. It hit a line of small craters in the sand and began to turn to starboard, careering towards Klemantaski, who, viewing events through a telescopic lens, misjudged the distance and continued filming. Hearing the approaching roar he looked up from his viewfinder to see Panjandrum, shedding live rockets in all directions, heading straight for him. As he ran for his life, he glimpsed the assembled admirals and generals diving for cover behind the pebble ridge into barbed-wire entanglements. Panjandrum was now heading back to the sea but crashed on to the sand where it disintegrated in violent explosions, rockets tearing across the beach at great speed."
I wondered if anyone had mentioned this, there is extant film of its misadventures, some of which is featured here

I'd take the assertion that , 'until recently, very few people knew of its existence,' with a liberal pinch of salt. It was after all featured in 'Dad's Army' "Dad's Army" Round and Round Went the Great Big Wheel (TV Episode 1972) - IMDb