personal defense

Personal defense weapons (PDWs) are a class of compact, selective fire, magazine-fed, submachine gun-like firearms. Most PDWs fire a small-caliber (less than 6 millimetres or 0.24 inches), high-velocity centerfire bottleneck cartridge resembling a scaled-down intermediate rifle cartridge, essentially making them an "in-between" hybrid between a submachine gun and a compact assault rifle. 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 PDWs' muzzle rise much easier to handle than assault rifles, especially considering the usually short barrel lengths.
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/infiltrators and thus have 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 hostililty is rare enough that a long-barrel service rifle would be an unnecessary burden during their normal duties.
Because of their lightweight, controllability, ease of operation and close-range effectiveness (can defeat a NATO CRISAT vest or an NIJ IIIA soft Kevlar armor at up to 200 metres or 220 yards), PDWs have also been used by special forces, paramilitaries, heavily-armed tactical police and even bodyguards.

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