The South Korean military was using old Colt M1911A1 pistols in the 1980s, and as they became worn out a new pistol was needed. This would be something designed and built domestically, and chambered for 9x19. The small arms division of the massive Daewoo industrial conglomerate, called Daewoo Precision Industries, spent several years in the mid 80s designing what would be adopted in 1990 as the K5 pistol. It took elements from the Beretta 92 and 3rd-generation S&W automatics, and the "fast action" trigger mechanism from FN and combined them into a compact, reliable duty pistol.

The "fast action" trigger, also called "triple action" or "double action plus" is a DA/SA trigger in which the hammer can be manually pushed forward after being cocked. This gives the system a hybrid trigger pull, with the weight of single action but the length of double - theoretically ideal for carry.

Daewoo imported K5 pistols to the US until 1997 through several different importers under the designation DP-51 (and also the DP-51C compact and the DP-40 in .40 S&W). By the late 90s Daewoo was in financial trouble, and the small arms division was eventually spun off into a separate company, called S&T Motiv. They began importing the K5 again circa 2012, not designated the LH9, through US company Lionheart Industries. Lionheart moved form importing the guns to manufacturing them in Washington in 2016, renaming them the Regulus and adding better sights, slide serrations, frame texture, and other commercial options. Lionheart was subsequently sold to a new US owner and its manufacturing moved to Georgia, where it was again renamed as the Vulcan 9 and released in 2023.

The Vulcan-9 remains mechanically the same as the original K5, but offers a variety of modern options, including threaded extended barrels and optics cuts. It's still a relatively compact pistol, but one that is now pretty well loaded with features (albeit for a quite high price).

Thanks to Lionheart for loaning me the three iterations of their company's pistols for this video!