The harquebus was the predecessor of the firearm known to modern folk as a musket. It was classified as a handgun, weighing in at under 6-7 kg; it consisted of a simple smoothbore barrel wedded to a wooden frame. Trigger mechanisms were rudimentary, but are important in distinguishing the harquebus from earlier hand cannons.

The term harquebus means 'gun with a hook' and may have originally come into use due to the early shape of the weapon. They were designed as firearm replacements for the crossbow, and early models retained the general shape of the crossbow, with a decorative or at least vestigial crosspiece in front.

Differing from hand cannon in its method of ignition, the harquebus owes much of its introduction to the invention of the slow match. A slow match consisted of a bit of twine soaked in a retardant fuel, typically ammonium nitrate, and then dried. When lit, it would smolder for an extended period without consuming the match, as well as being resistant to extinguishing. These were quickly popular with cannoneers, as it allowed them to easily retain ready flames with which to touch off their pieces. German gunsmiths in the mid 15th century hit upon the idea of fastening a metal piece to the side of a firearm in the shape of a large 'S' with a pivot in the middle and a set of clamps at the top end. The clamps would hold a slow match, and when the contraption was pivoted around the center by moving the bottom of the 's' (where the holder gripped the weapon) the slow match would be brought into contact with the flashpan around the touchhole - and BANG.

The craftsmen most able to produce moving durable mechanisms of metal were, at the time, locksmiths; they were pressed into service to manufacture these firing mechanisms. As a result, to this day, mechanisms to fire a gun are called 'locks' - and this, the matchlock, was the first of its kind. It made the difference between a simple hand cannon and a harquebus.

Eventually, the matchlock become more complex with the addition of a side-mounted flashpan, then with covers for the flashpan to protect the primer, and eventually with a spring to drive the match against the primer when the match holder had passed a particular position. The 's' of metal migrated from the outside of the gun to the interior of the butt, which grew to accomodate it as well as allow the firer to hold the weapon against his shoulder (rather than the original - and painful-looking - practice of bracing it against the breastbone). The interior-mounted 's' piece evolved into the modern trigger mechanism by splitting into three pieces: the arm holding the match, a trigger at the bottom, and a connecting piece known as the sear. Around 1500, the matchlock was joined by the wheellock, which rather than using a lit match rotated a metal cylinder against iron pyrites (pyrite - fire stone - get it?) to produce sparks inside the flashpan. This allowed the weapon to be carried charged, without requiring the ignition of the match; however, wheellocks were complex and fragile, which kept them out of general weapons and in the guns of nobles.

The term harquebus came to mean a smaller shoulder arm, midway between a musket and the newer pistols; more of a carbine in size. Typically, a harquebus of the 16th century was a weapon that was highly ornate or customized, used as a noble's personal arm rather than the weapon of a common soldier - occasionally with a wheellock rather than a matchlock. The musket was the next step; a larger weapon, longer and more accurate due to better powder mixtures and improved methods of barrel construction. The introduction of the flintlock finally made the carrying of a charged weapon practical, as the flintlock was much simpler, hence cheaper and more durable, than the wheellock. The flintlock musket eclipsed the matchlock harquebus by the end of the 17th century.