Developed at a turning point in air-to-air combat, the AIM-9 Sidewinder missile was the world’s first infrared-guided — or heat-seeking — missile, forever changing not only the dynamics of dog fighting, but the ways in which combat aircraft are designed, built, and employed in war. But most surprising of all is that this game-changing missile wasn’t developed with backing from the U.S. military… but rather, in spite of it.

The air combat of World War II was largely dominated by daring pilots flying in close quarters with the enemy in an effort to engage them with a variety of onboard cannons. Air-to-air rockets had proven effective in limited use during World War I against observation balloons and again in World War II against bombers, but the unguided nature of these weapons severely limited their range and efficacy.

By the end of World War II, the advent of radar had made the prospect of fielding guided air-to-air missiles a reality. By 1947, both the U.K. and the U.S. were quickly developing a new bevy of radar-guided weapons like the U.K.’s Fairey Fireflash and America’s AAM-A-1 Firebird. These early air-to-air missiles were complex pieces of equipment — which meant they were difficult and expensive to produce.

But physicist William B. McLean, a Navy physicist at the U.S. Naval Ordnance Test Station (NOTS) in the Mojave Desert — a man whose professional responsibilities notably did not include new weapon development — thought he knew better than the prevailing wisdom of the day… And despite the Navy’s disinterest and a fair bit of harassment from his peers, he set out to prove it.

One year before contracts were awarded for these early radar-hunting missiles, William B. McLean and his team were working with lead-sulfide proximity fuzes that were designed to be sensitive to infrared radiation (heat). Well aware of developmental radar-guided missiles and their complexity, McLean reasoned that if you could make a fuse that detonated when it sensed infrared radiation, it might also be possible to develop a guidance system that used that same heat-sensing ability to adjust course mid-flight.

There was just one problem… McLean had no experience designing these sorts of weapons.

McLean earned his........

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