Around the beginning of this millennium, the Chinese invented a mixture of chemicals loosely known as "gunpowder." Gunpowder has proven itself to be one of the most, if not the most, important invention of this millennium.
Gunpowder and the machines that employ its massive potential for energy have dominated every major military conflict since the 1600s. Guns came into being when the Europeans adopted gunpowder from the Chinese, who had primarily used it as a fuel for fireworks and very crude cannons. They bored a hole in a cylinder of metal, drilled a small hole in the closed end, poured in some gunpowder and a tight-fitting lead ball, applied some source of fire to the touchole at the end, and resulting "boom" signified the invention of the gun.
The first firearms were bulky, heavy, and slow to load. The earliest guns employed by medieval armies were nothing more than a long cylinder of metal similar to the type described above. The shooter fired the weapon by applying a slowly burning piece of rope, or match, to the touchole at the end of the firearm. There were no provisions for aiming the device, and fired projectiles were more likely to be lobbed onto opposing armies than fired directly at them. At the same, massive cannons were developed to fire large round balls great distances at besieged towns. Any monarch who could afford such monstrosities could only utilize them when besieging a city, due to the enormous weight of both cannon and projectile. However, once employed, they were the scourges of cities that had once depended on their tall, thick walls being impenetrable. As cannons became more and more powerful, no city could stand in the way of an army employing such weaponry.
In the mid-1600s, gunsmiths began to experiment with lighter and more accurate firearms for foot soldiers. The guns which dominated the English Civil War were still bulky and heavy, but were easier to load, and provisions were being made to compensate for their weight. Monopods with forks attached to one end were employed to support the guns' weight. The "matchlock" came into active service, allowing the match aforementioned to be held in a hammer which, when the trigger was pulled, would allow the glowing rope to fall into a pan of gunpowder, igniting the powder charge in the barrel. The matchlock was the first lock type to be heavily manufactured. However, the gun itself was still relatively bulky, inaccurate, and could only be fired once to twice a minute by a capable marksman.
For a short time in the waning days of the matchlock, a new, more radical lock was introduced, the wheelock. In this new lock type, a piece of iron pyrite was held by a hammer against a wheel with extremely rough edges. The wheel would then be turned by the operator using a special key. The trigger being pulled caused the wheel to rotate quickly, grating off pieces of flaming metal and throwing them into a small powder charge that would in turn ignite the main charge in the barrel. However, the wheelock was very expensive to manufacture, and the key used to crank the wheel prior to firing was easy to lose and break. The wheelock was quickly abandoned in favor of a new and more reliable lock type, the flintlock.
Invented in the late 1600s, the flintlock stands today as the lock type with the longest tenure in history. The premise was simple. When the trigger was pulled, a hammer holding a piece of flint would fall forward, striking a piece of steel, shaving off sparking shards of metal, allowing them to fall into a small powder charge which, when ignited, lit off the main powder charge in the barrel.