At the dawn of air-to-air warfare, pilots did whatever they could to bring down their prey, up to and including carrying weapons in the cockpit so they could fire on the enemy. Obviously, this wasn't effective, and before long designers started adding a second seat with a swiveling machine gun. This was slightly better, but still a far cry from the lethality pilots needed. Then, the synchronization gear was born.
First dreamed up by Germany's August Euler and perfected by aviation legend Anthony Fokker, a synchronization gear allowed a nose-mounted machine gun to fire between the propeller as it spun. While fighters were already using wing-mounted guns, sticking one on a fighter's nose made bringing down targets even easier for pilots. If this sounds like magic, it probably is.
And after seeing it in person, magic might actually be a good explanation for this piece of technology. The Slow Mo Guys YouTube channel set their high-speed cameras on a rigged-up gun, prop, and synchronization gear to explain how it works. Then, they took off the synchronization gear to see just what would happen to the propeller. The results? Yeah, we're still calling it magic.