The arquebus (sometimes spelled harquebus, harkbus or hackbut; from Dutch haakbus, meaning "hook gun") was a primitive firearm used in the 15th to 17th centuries.
Like its successor, the musket, it was a smoothbore firearm, although somewhat smaller than its predecessors, which made it easier to carry. It was a forerunner of the rifle and other longarm firearms.
Heavy arquebuses mounted on wagons were called arquebus à croc. These carried a ball of about 3.5 ounces.
As low-velocity firearms, they were used against enemies that were often partially or fully protected by steel-plate armour. Plate armour was standard in European combat from about 1400 until the middle of the 17th century. This was essentially the era of the arquebus. Good suits of plate would usually stop an arquebus ball at long range. It was a common practice to "proof" (test) armour by firing a pistol or arquebus at a new breastplate. The small dent would be circled by engraving, to call attention to it. However, at close range, it was possible to pierce even the armor of knights and other heavy cavalry. This led to changes in plate design like three-quarter plate and finally the retirement of plate armor altogether.
The arquebus was fired by a matchlock mechanism and had a larger bore than its predecessors. From the middle of 16th century, newer wheellock mechanisms were used instead of older matchlocks. The flared muzzle of some examples made it easier to load the weapon. The name 'hook gun' is often claimed to be based on the bent shape of the arquebus' butt. It might also be that some of the original arquebuses had a metal hook near the muzzle that may have been used for bracing against a solid object to absorb recoil. Since all the arquebuses were handmade by various gunsmiths, there is no typical specimen.