Close Quarters Combat Weapon System

The Close Quarters Combat Weapon System, otherwise known as the Combat Knife is a United Nations Space Command infantry-sized knife used for multi-purposes.

Overview
The multi-purpose combat knife has a 20 centimeter (7.9 inches) blade made of high carbon steel coated for corrosion resistance and is 43.3 centimeters (1.42 feet) sheathed. All UNSC troops are issued with a combat knife for close quarters combat or in situations when ammo is scarce. It is also balanced for throwing. It only appears in the novels and on the backs of Orbital Drop Shock Troopers in Halo 2 and Halo 3, and as an aesthetic addition to the CQB armor.

Appearance
One of the few times a combat knife can be seen in game is on the lower backs of ODSTs and on the left chest of the C.Q.B chest plate armor permutation, though they are never used in combat. It also has a serrated edge like other combat knives as mentioned in Halo: The Fall of Reach. It currently represents certain difficulty levels in the Halo Trilogy. Normal has a single sword, Heroic has two crossed swords, and Legendary is represented by a shot Elite skull with two crossed swords on top of a shield bearing the Marathon symbol.

History
For use in battle, knives have been used almost since the dawn of warfare, as a sharp piece of metal proved effective during a period of time where projectile weapons were not readily available. The combat knife later branched off and became a sword, while others used daggers. For hundreds of years, knives and swords became the weapon of choice for soldiers. Even after the invention of the firearm, knives were still used as bayonets for close-quarters-combat. As the intent of war shifted from trench warfare to attrition warfare, knives became last-resort weapons. By 2553, the UNSC is still using knives, showing that such an easily accessible and created weapon still runs strong even thousands of years later.

Trivia

 * The ODST Action Figure, made by Joyride Studios, has a Combat Knife that can be held by the action figures hand.
 * It was Spartan-104's (Fred) trademark weapon next to the MA5B Assault Rifle.
 * In Halo 3 Concept Art for EGM, a Spartan is shown with a Combat Knife on his right leg, however this was just an artistic look for the ODST armor.
 * It was intended to be used in the early Halo: CE build but was cut before it made it into the final game.
 * It can be seen on the shields when selecting the difficulty levels. One on Normal and two crossed over each other on both Heroic and Legendary, the latter also having an Elite skull.
 * The "containment device", if you will, for the Combat Knife on the CQB Armor Permutation seems much more complex in appearance than the sheath of the ODSTs.
 * Modern military forces use combat knives as a sort of utility tool rather than as a close-quarters weapon system. It is unknown why it's general role would have changed over the course of 500 years, it is most likely Bungie's misconception of today's combat-knife. Or possibly it was used as both( as maintnence and unjamming a jammed weapon aren't often mentioned in the books or game)
 * On Normal or higher combat-knives are seen on the difficulty shields.