Although war is, on balance, something of a global blight, it's also got a silver lining: technological advances seem to happen rather quickly during it. When the war's over, the survivors get to pick up the results. As such, technologies from the internet to aviators all owe their heritage to history's greatest disasters.
The Global Positioning System is probably the most famously military in the world. Designed during the Cold War to provide a navigation system for the Polaris submarine-launched intercontinental ballistic missile, the GPS platform consists of 24 satellites that, combined, let a receiver anywhere in the world calculate its accuracy down to just a metre or two.
However, GPS wasn't always properly accessible to civilians. Originally, there were two signals of different quality -- the civvie one, and that reserved for the US military (and its closest buddies, of course). Known as Selective Access, this was only disabled on May 2nd, 2000, allowing civilians to get accuracy down to centimetres rather than metres. According to the US's Director of Science and Technology at the time:
With SA activated, you really only know if you are on the field or in the stands at that football stadium; with SA switched off, you know which yard marker you are standing on.
Men have been shaving pretty much since we discovered how to get a sharp bit of flint; but it's always been a bit dicey, with a sharp blade pressing against the jugular (it's not called a cut-throat razor for nothing). The modern safety razor, invented by Gillete, changed all of that.
It was first patented in 1901 by Mister Gillette, but didn't take off until Gillette got the contract to supply American troops in WWI. After all the victorious GIs came home, safety razors took off, and our baby-smooth cheeks haven't been the same since.
Arguably the most useful invention on the list, duck tape was invented by Johnson & Johnson (of baby powder fame) in the midst of World War II, to fill a requirement for ammunition boxes to be sealed against the elements.
Made of adhesive backed by cotton duck cloth (hence the name) and in military green, it only took on the iconic silver-backed plastic version known today in the mid 1950s, when people started using it to seal air ducts (which is why the name has been semi-bastardised to 'duct tape' by some people).
Common derivatives include gaffer tape (black, and designed to be removed cleanly), sniper tape (green and cloth-backed, issued by the Army, batshit-expensive and batshit-useful), all the way up to £200-per-roll aluminium speed tape, used to fix airplanes and probably patch up holes in flying unicorns.
Although four-wheel-drive has been knocking around since the dawn of the car (fun fact: Porsche debuted an electric four-wheel-drive car back in 1901), true off-roaders didn't exist until, surprise surprise, the Second World War and the iconic jeep.
Although who did the original design is a source of much controversy, a prototype manufactured by Bantam (the renamed American arm of Britain's legendary Austin), the Bantam Reconnaissance Vehicle, was the first proper off-roader to see the light of day. Having impressed the military authorities, the contract for construction eventually went to Willys, and the Jeep was born. Post-war, Willys retained the upper hand; even brands we associate with 4x4 nowadays, like Land Rover, only got their start through imitating Willys designs.
Although weather forecasting as a science has been improving for millenia, two milestones stand out, and both of them are military. The first is the work of Sir Francis Beaufort, a captain in the Royal Navy during the Napoleonic Wars, and the man who designed the world's first standardised system of weather reporting for said Navy -- most notably, the Beaufort scale for wind speeds, ranging from 0 ("smoke rises in a straight line") to 12 ("abandon ship") and still used up to this day.
The second breakthrough was the establishing of a vast weather forecasting system in the States by the US Army Signal Service. Owing to a high number of ships lost on the Great Lakes to storms, the US Congress ordered the Secretary of War (a cool political role if ever there was one) "to provide for taking meteorological observations at the military stations in the interior of the continent and at other points in the States and Territories...and for giving notice on the northern (Great) Lakes and on the seacoast by magnetic telegraph and marine signals, of the approach and force of storms".
The king of accidental discoveries, the concept of using electromagnetic radiation to cook food was actually stumbled on during WWII, by an engineer named Percy Spencer, who was testing a high-powered radio set.
He only discovered the cooking power of the magnetron he was working on when it melted a chocolate bar in his pocket (imagine the Health & Safety forms nowadays: errant radiation AND burn hazards). The first commercial microwave oven was manufactured and sold by Raytheon in 1947, but costing about £30,000 and taking up the same space as a fridge, it wasn't a huge hit. It wasn't until a £2,000 model about the same size as modern microwaves was introduced in 1967 that TV dinners really caught on.
The oldest technology on the list, canning was a technology designed during the Napoleonic wars, in response to a need (mostly from the Navy) for a good method of preserving food. At the time, preservation relied mostly on salt: beef in brine and salted pork was the backbone (well, along with rum) for the Royal Navy in Nelson's time.
Salting was relatively effective in preserving food for a few months at a time, but required hundreds of finicky casks, and only really worked on meat -- the only vegetable the Navy could preserve was peas, hence the scurvy epidemics that used to plague sailors.
Thus, the French military decided to offer a cash prize to anyone who could come up with a solution. Nicolas Appert, a French brewer, took up the mantle, and worked out that cooking food inside a glass jar worked as a means of preservation. Although the principle was sound, owing to glass being a fairly crap material for transporting large amounts of food, the jars were quickly replaced with cans. The Napoleonic wars ended in 1815, before the can could really take off, and it took until the mid 1820s and the patronage of the Royal Navy for cans to become popular, especially for long-range surveying missions.
Ray-Bans (or Rey-Ben, if you're shopping in the seedier parts of Camden) are the iconic aviators, and for good reason: in the mid 1920s, US Air Force pilots were reporting problems with sunshine, and needed a pair of sunnies with good coverage to ease their pain.
Bausch & Lomb, the American eye care company, stepped in with a solution: the aviators. Originally in plastic and with green lenses, the design was quickly refined and diversified, to give the classic Ray-Ban-branded aviators we know and love now, and even the hilarious Shooters (with a ring in between the eyes, where pilots could store their cigarettes while they were busy shooting bad guys down).
Who created the modern-day internet has been the topic of many a meandering Quora thread; but one thing is clear, and that's the role that the Advanced Research Projects Agency (now DARPA, the US military's R&D department) played with their precursor to the internet, ARPAnet.
Although the internet came about through the collaboration of dozens of different scientists and networks, ARPAnet stands out as the forerunner. Created at the behest of the US government to connect computers at the Pentagon and Cheyenne Mountain, the US nuclear weapon control centre, ARPAnet quickly expanded to include research institutions and universities, and was the testbed for much of the infrastructure underlying the internet, like the crucial TCP/IP protocols.
Although fundamentally not the most interesting technology in the world, synthetic rubber is big business: 10 billion tonnes of synthetic rubber are produced every year (that's two-thirds of the world's rubber supply), and everything from cars to small children would be lost without it.
Although synthetic rubber was successfully synthesised by German and Russian scientists in the early 20th century, production didn't kick off until (once again) WWII. With the Axis powers controlling most of the world's natural rubber supplies (thanks to Japan's conquest of Asia), the US funded a vast amount of research and production of synthetic rubber, for everything from car tyres to O-ring seals. The result was styrene-butadiene rubber, a hard-wearing compound that still makes up around 50 per cent of car tyres today.