By the summer of 1942, the United States Marine Corps was preparing for a new kind of warfare in the Pacific, but its fighting knives had yet to catch up. Marines heading overseas carried everything from aging World War I trench knives to commercially purchased hunting blades, with little consistency between units. The fighting on Guadalcanal demonstrated how useful a dependable fixed blade could be, particularly in the dense jungles and difficult conditions of the Solomon Islands. Marines needed something they could rely on for close combat, but they also needed a knife capable of handling the countless cutting and camp chores that came with life in the field. The search for a standardized fighting and utility knife would eventually produce the KA-BAR USMC Fighting Knife, a design that would become inseparable from American military service for generations.

Without a suitable standardized alternative, many Marines purchased their own knives before deploying overseas. Commercial hunting knives from companies such as Western States Cutlery became popular, particularly the L76 and L77 patterns, which featured long clip-point blades and leather handles. These knives offered practical cutting edges and familiar hunting-knife construction, although they had not been designed specifically for military service. In May 1942, a Marine Corps memorandum recommended sheath knives as both weapons and general utility tools, particularly for cutting landing lines, clearing vegetation, and performing tasks for which a bayonet was poorly suited.

One of the companies involved in developing a knife already had several decades of cutlery manufacturing behind it. The business that would eventually become KA-BAR traced its origins to the Tidioute Cutlery Company, established in Pennsylvania in 1897 and producing knives by 1898. Wallace R. Brown purchased the company's assets in 1902 and operated the business as the Union Razor Company. As its product line expanded beyond razors, the name was changed to Union Cutlery Company in 1909. The company subsequently relocated to Olean, New York, where it established manufacturing operations in 1911. By the early 1920s, Union Cutlery was producing a variety of hunting, sporting, and pocket knives, several of which carried the KA-BAR trademark.

The origin of the KA-BAR name has become a story of its own. In the early 1920s, an Alaskan hunter reportedly shot a Kodiak bear, only for the wounded animal to attack and knock his rifle from his hands. With no way to use his firearm, the hunter drew his Union Cutlery knife and managed to kill the bear. Grateful that the knife had saved his life, he later sent the bear's hide to company president Wallace Brown, along with a letter describing the encounter. The hunter's account of using his knife to "kill a bear," often retold as "kill a bar," became the KA-BAR name. Union Cutlery adopted KA-BAR as a trademark in the early 1920s, registering it in January 1924. By the time the United States entered World War II, KA-BAR was already an established name on Union Cutlery hunting knives.

As the Marine Corps worked toward a standardized fighting knife in 1942, Union Cutlery became involved in the development process. Under company president R. Danforth Brown, they worked with Marine officers John M. Davis and Howard E. America to develop a design suitable for both combat and general utility work. The existing U.S. Navy Mark 1 utility knife and several commercial hunting patterns provided starting points, but the Marines wanted a longer and stronger blade capable of handling the demands of Pacific warfare. The design went through several revisions to the blade, guard, handle, and pommel before a satisfactory configuration was achieved.

By late 1942, the Marine Corps had approved the design for procurement under the designation 1219C2, commonly described as the Fighting/Utility knife. Production began as American manufacturers expanded their wartime operations, and the first deliveries reached Marines in the Pacific in early 1943. With the new knife entering service, the Marine Corps finally had a standardized alternative to the wide variety of commercial and specialized blades that had been used in earlier deployments.

Union Cutlery was one of four manufacturers selected to produce the fighting/utility knife during World War II. Camillus Cutlery Company, PAL Blade Company, and Robeson Cutlery Company also manufactured knives to the military pattern, each using its own markings. Union Cutlery stamped its knives with the KA-BAR trademark, usually accompanied by a USMC designation, while the other manufacturers identified their own factories. Although all four companies worked from the same general specifications, surviving wartime examples show small differences in blade finishes, markings, guards, and pommel construction. Camillus became a particularly large producer of the pattern, supplying substantial numbers of knives for military service.

As production increased throughout 1943 and 1944, the fighting/utility knife became a familiar piece of equipment among Marines operating across the Pacific. It accompanied troops during the campaigns that followed Guadalcanal, including the fighting in the Marshall Islands, the Marianas, Peleliu, Iwo Jima, and Okinawa. The knife was carried by infantrymen, Raiders, reconnaissance personnel, and other Marines whose duties brought them into close contact with the enemy or required frequent use of a fixed blade.

Although designed with combat in mind, the fighting/utility knife was used for far more than fighting. Marines cut rope and webbing, opened ration tins and ammunition packaging, cleared vegetation, prepared food, and performed repairs around their positions. It was also pressed into rougher service, including digging shallow holes, driving tent stakes, and opening wooden crates. The National Museum of the Marine Corps preserves accounts of Marines using the knife for everything from ordinary cutting work to pounding nails. These were often tasks far outside what a fighting knife would ordinarily be expected to perform, but they became part of everyday life during extended operations in the Pacific.

Eventually, the name KA-BAR began to spread beyond knives manufactured by Union Cutlery. Marines commonly referred to the entire fighting/utility pattern as a KA-BAR, regardless of whether a particular knife had been produced by Camillus, PAL, Robeson, or Union Cutlery itself. By the end of World War II, the KA-BAR name became so closely associated with the Marine Corps fighting knife that its original name was often overlooked.

The end of World War II brought an enormous reduction in military procurement, but the fighting/utility knife continued to accompany American troops. Surplus knives remained in military inventories and were issued during the Korean War, where Marines once again encountered difficult terrain, extreme weather, and prolonged field operations. Many of the same knives that had been manufactured for service in the Pacific remained useful years after their original production. The pattern also continued to be manufactured under later military contracts, with companies such as Camillus, Utica, Conetta, and eventually Ontario producing versions for the armed forces.

Meanwhile, the success of Union Cutlery's KA-BAR had become far more recognizable than the company name itself, prompting them to rename to KA-BAR Cutlery, Inc., on May 7, 1952. The business was still under the leadership of Danforth Brown, whose involvement in the wartime fighting knife had connected the family-owned cutlery company to one of the most recognizable military knife patterns of the twentieth century. The name change also came during a difficult period for the American cutlery industry, as manufacturers adjusted to declining military orders and renewed competition in the civilian market.

In 1954, Brown attempted to improve the company's position by relocating manufacturing operations from Olean, New York, to Dawsonville, Georgia. The move was intended to take advantage of lower operating costs and local economic incentives, but it proved unsuccessful. KA-BAR returned to Olean in 1956, where much of its original manufacturing equipment and workforce remained available. Danforth Brown died in 1960, bringing an end to the family's long period of leadership. KA-BAR passed through several owners before being purchased by Cole National Corporation in 1966.

While the company changed hands, the fighting/utility knife continued its military service. During the Vietnam War, Marines and other American personnel carried both older surplus knives and later-produced examples of the same basic pattern. Its broad blade was well suited to the practical work associated with jungle operations, although many servicemen also purchased their own knives from military exchanges or commercial retailers.

In 1975, Richard "Dick" Sturm founded the KA-BAR Collectors Club, renewing interest in the company's historical designs. The familiar USMC fighting/utility pattern returned to manufacturing in Olean through the CUTCO Cutlery facility, which produced knives for KA-BAR's corporate owner. A commemorative edition followed in 1976, celebrating the Marine Corps' bicentennial with decorative markings and special presentation details. The success of these collector-oriented knives encouraged a return to standard production, allowing civilian buyers and veterans to purchase newly manufactured versions of the familiar design.

Another major change came in May 1996, when Alcas Corporation, the parent company of CUTCO Cutlery, purchased the KA-BAR product line and assets from Cole National. The acquisition brought the brand back under Olean-based ownership and allowed production of the USMC fighting/utility knife to continue at the CUTCO manufacturing facility. KA-BAR expanded its offerings under the new ownership while maintaining the military pattern as a central part of its catalog. The company later relocated its headquarters to Homer Street in Olean in 2003.