Personal defense weapons (PDWs) are a class of firearms intended for self-defense and security rather than warfare and infantry. Most PDWs fire a small-caliber (less than ), centerfire bottleneck cartridge resembling a scaled-down intermediate rifle cartridge, essentially making them an "in-between" hybrid between a submachine gun and a carbine. The use of these rifle-like cartridges gives the PDWs much better ballistic performance (effective range, accuracy and armor-penetrating capability) than conventional submachine guns, which fire larger-caliber but slower and less aerodynamic handgun cartridges. The low recoil of these "sub-intermediate" cartridges also makes muzzle rise on PDWs (which typically have short gun barrels) much easier to handle than short-barreled rifles, especially when shooting full-auto or in burst fire. The name describes the weapon's original conceptual role: as a compact but powerful small arm that can be conveniently carried for personal defense, usually by support personnel behind the front line such as military engineers, logistic drivers, medical specialists, artillery crews or signallers. These "second-line" personnel are not strictly combat troops expected to directly engage the enemy, but may still be at risk of encountering decently equipped (and often well-armored) hostile skirmishers and infiltrators, therefore having to defend themselves in close quarters. Such encounters will warrant an effective weapon that is easy to use while having sufficient firepower to suppress enemy charges and hold them beyond a safe perimeter to prevent the defenders from being overrun, but the risk of hostility is rare enough that a standard service rifle would be an unnecessary burden during their normal duties. Because of their light weight, controllability, ease of operation and close-range effectiveness (can defeat a NATO CRISAT vest or an NIJ IIIA soft Kevlar armor at up to ), PDWs have also been used by special forces, paramilitaries, heavily armed tactical police and even bodyguards. History In the 19th and early 20th centuries, shortened versions of the infantry rifle were issued as "carbines" for cavalry troops and gun crews. This designation was dropped as infantry rifle designs became shortened overall, such as in the Short Magazine Lee–Enfield rifle. Thereafter, handguns were typically issued as self-defense weapons. However, they were not effective in most close combat situations. As a result, during the First World War, the Mauser C96 and artillery versions of the Luger pistol were issued with attachable shoulder stock holsters, which allowed for greater control and accuracy. During World War I, the United States secretly