During WWII, the British launched nearly 100,000 weather balloons trailing long metal wires toward occupied Europe, causing power outages when they shorted out power lines and causing at least one German power station to burn down. The US military “rediscovered” this during training operations in the San Diego area a few decades ago when metallic radar cloaking chaff accidentally drifted into a substation causing a widespread power outage. This led to development of ordnance that released carbon fibers for the same effect. It was used during the Iraq war.
David “Carbine” Williams, who helped invent the M1 Carbine, was a convicted murderer and created innovative gun ideas while in jail. He was convicted of the shooting of a sheriff who busted his illegal moonshine still. He was released after his family argued his inventions could help America.
The CIA has a “Heart Attack Gun”. The gun would shoot a dissolving dart that would cause what appeared to be a natural heart attack. The dart would only leave a small red dot and the poison would denature so quickly, it would unlikely be discovered in autopsy.
In the civil war, the commander of the Union “lightning brigade” personally took out a loan to buy his soldiers advanced new repeating rifles because the government would not supply them. Using the firepower advantage afforded by the new rifles, his brigade proved extremely effective in combat.
A villager in China unknowingly used a hand grenade to crack walnuts for a quarter century, until he saw the grenade in a government flyer.
During WW2 the Japanese built a deathray inspired by ideas from Nikola Tesla, the problem was that enemies would have to stand perfectly still for 10 minutes before it would work.
The WWII era B-29 bomber didn’t require fighter escorts because it had a computer aided gunnery systems that allowed incredible firing accuracy against attackers. One B-29 was attacked by 79 fighters at once, but was able to fight them off and down 7 of them in the process.
During combat, a US Marine’s rifle jammed, so he called customer service to help him fix it.
New Zealand’s first tank (the Bob Semple tank) was built from a tractor, sheet metal and 6 machine guns. When ridiculed for the design Bob Semple said “I don’t see anyone else coming up with any better ideas.”
Portuguese soldiers used black swords in the Age of Discovery in order to not reflect the light and announce their presence on ships, avoiding also its rusting when used near salt water.