It was Heckler & Koch's entry into the U.S. military's Close Assault Weapon System program.

The development of the HK CAWS started in response to the JSSAP requirement for Repeating Hand-held Improved Non-rifled Ordnance (RHINO),[2] which itself grew out of the Special Operations Weapon (SOW) project.

[3] RHINO specified a magazine capacity of 10 rounds, a requirement for the new ammunition to be incompatible with commercial 12 gauge shotguns, that felt recoil to be no greater than a Remington 870P firing M162 or M257 buckshot cartridges, and that the system provide penetration and incapacitation capability significantly better than M162 and M257.

The main goal of this program was to develop a new generation personal firearm, capable of firing high-impulse, multiple projectiles with effective range of 100–150 m (110–160 yd).

One of the teams entered in the CAWS race was Heckler & Koch Germany, coupled with Winchester Corp. United States.