In 1989, NATO published a set of
requirements that requested a new type of firearm with rounds capable of
penetrating body armor. Called the Personal Defense weapon, or PDW, it was
meant to replace weapons, such as pistols and submachine guns, whose caliber
was found wanting against ballistic protection. Several companies went on to
design PDWs, with the most successful, if not the most visible version, coming
from German arms company Heckler & Koch.