With every great war, every global conflict and galactic fight for survival there are weapons. Billions of weapons, munitions, vehicles and ships. Soldiers bravely throwing their lives at the enemy, utilizing cutting edge technology and armor.
But all that equipment isn't free, and even in war there are those who stand to profit. Defense contractors in the modern day make billions, and sometimes even trillions of dollars (USD) on arms sales. Two of the most prominent United States Defense Contractors, Lockheed Martin and Northrup Grumman, make upwards of several billions dollars annually to supply the United States and its allies with the equipment they need to take the fight to the enemy.
Halo's universe is no different than our own, where weapons contractors and defense conglomerates stand to make a large profit on the galactic wars of the future. From the corporations who specialize in cheap, affordable arms and armor; to the cutting edge corporate mega-business' that research experimental munitions for the UNSC.
Put on your good suit and pants. Let's discuss the terms.
If there is a corporation which can be pointed to, which supplied the weapons and armor that saved humanity during The Covenant War; it is Misriah Armory. Throughout the war with The Covenant, Misriah was responsible for manufacturing some of the most ubiquitous and reliable weaponry to the UNSC. Most of the weapons during the war, in fact, were manufactured by Misriah. If the war with The Covenant had a "god of the forge," Misriah was the hammer.
Based on the planet Mars, in the home system of humanity, Miriash has massive forges scattered throughout the planet. These forges, during the war, worked day and night manufacturing new arms and vehicles at an endless rate. The corporation also has holdings on multiple planets including Reach and Cascade, which also continually (and still) supply munitions to the UNSC.
Perhaps the most enduring weapon of The Covenant war was manufactured by Misriah, the MA5 individual combat assault weapon.  The MA5 was, and still is, the workhorse of the UNSC military. Firing 7.62x51mm Full Metal Jacket heavy rounds at an incredible rate of fire, the MA5 saw action in every major conflict of the war, and beyond. Soldiers slogging through mud, swamps, sand and heavy rain swore by the rifle's reliability to preform in extreme conditions. The weapon is not only a capable machine of war, but also one of pathfinding. All MA5 variants are fitted with an OLED screen near the top of the receiver. The screen houses a series of combat electronic suites designed to function as a compass and provide accurate ammo counts. This was indispensable during the war, where soldiers could merely look down at the display, rather than wait for a dry clip. It is still in service, under the "D" variant.
Alongside the MA5, and just as recognizable, is the M6 heavy pistol. The M6 is a masterwork of ballistic technology, firing an extremely heavy .50 caliber armor piercing sidearm round. During the war, the M6 was the preferred weapon of officers, whom usually carried the up-sized "D" variant which fires high explosive rounds. These rounds blow away Covenant shielding and turn un-shielded targets into a mist of blood. The only disadvantage to the M6 is its weight, which limits its distribution among personnel. In addition, the M6 weapons have a tendency to drop casings on the wielder's foot, causing snap reactions that decrease overall aim and target acquisition. That said, multiple variants, including silenced and scoped versions, are in service with both military and civilian sectors. 
Misriah also manufactured some of the most important vehicles of the war, like the D77-TC Pelican dropship (all variants) and the M12 Warthog series of transport vehicles. Both vehicles were indispensable, moving soldiers from battle to battle and providing mobile fire support. 
Misriah pioneered the standard Marine and ODST armors and also manufactures a few low-end MJOLNIR power armor variants intended to be cheap, yet effective. These include the ODST upgraded variants and Athlon light weight chassis variants. 
The full list of arms from Misriah is staggering, and if not for their forges humanity would have been severely out-gunned during their conflict with The Covenant.
Acheron Security/Chalybs Defense Solutions/Naphtali
(Due to these corporations all sharing patents and licenses I am treating them as a conglomerate/parent.)
Acheron Security/Chalybs Defense Solutions/Naphtali conglomerate are three separate entities which share technology, patents and licenses for various weapons, vehicles and armors. ACN is responsible for some of the most ferociously powerful weapon platforms available to the UNSC. From Railguns, to main battle tanks, ACN is the leader of overkill.
All three corporations which are part of ACN were at one point based on the Outer Colony of Meridian, before it was glassed by The Covenant in 2551. The ACN then moved its operations to Earth and the planet Cascade, where it directly competes/collaborates with the technology focused company, Hannibal Weapons Systems. ACN, over the years, have been responsible for manufacturing the UNSC's most potent man potable weapons systems. Specializing in compact, yet utterly lethal firearms. ACN is also one of the few entities allowed to manufacture nuclear weapons for the the military.
Their claim to fame however, was the production of the M808 Scorpion, which is the principle main battle tank of the UNSC. The M808 is heavily armored, features four interlinked tread systems to maximize mobility and can be fitted with a wide range of weapons systems. The tank supports up to six crew, with one driver, one turret operator and four "hang on" rails to support infantry passengers. The M808 can reliably deal with most, if not all, armored threats placed ahead of it. There are reports of M808s still functioning while missing treads, on fire and excessively sparking. All at the same time. During The Covenant war, the M808 was responsible for taking out Covenant heavy armor, as well as grouped infantry. It served in almost every major conflict, and is respected by its operators for being reliable even when it has suffered catastrophic damage. During the battle of Reach, a single M808 operated by Spartan III Noble 6, was used to breach an ONI facility under heavy fire. The tank survived multiple air raids, Wraith plasma mortars, plasma bombardments and small arms fire before reaching its destination. It remained functional. 
ACN's most recent arms development is pioneering magnetic induction in a linear assembly. The result is the ARC-920 Railgun. The 920 is a compact linear acceleration rifle, which uses magnetic currents to propel a small tungsten rod at speeds exceeding mach eleven. The result is a round which travels so fast the friction with the air alone causes the projectile to super heat the atmosphere around it into plasma. Impact is devastating, with a single round able to completely obliterate most targets. The 920 has several variants, including the faster firing "Whiplash," which features proximity fused rounds and duel roud magazines. The other variant is ACN's poster child weapon, the "Arclight." The Arclight is a modified 920, which uses extreme electro-magnetic currents to propel an explosive tungsten round at even faster speeds. Most targets, be it infantry or armor, do not survive the impact of the round. Covenant Banshees have been sighted being turned into purple confetti when hit by an Arclight round, and infantry unfortunate enough to be impacted are turned into vaporized mist. 
ACN also supplies the UNSC with the M510 Mammoth, an extremely large assault/siege vehicle which acts like a form of ground based carrier. It is armed with multiple turrets and a miniature version of the UNSC's magnetic accelerator cannon. 
ACN manufactures several high powered MJOLNIR armor systems, including the durable Pioneer-class and lethal Noble-class. These armors are considered to be in the "mid-range" in terms of cost and durability.
ACN has one specific purpose, and that purpose might well have played a huge role is humanity's victory over The Covenant. "Devastation first, practicality second."
Hannibal Weapons Systems
Perhaps no other corporation during, or after, The Covenant war was/is as active and responsible for humanities' continued technological superiority than Hannibal Weapons Systems.
Hannibal Weapon Systems is named in reference to Hannibal, an infamous Carthaginian warlord who is considered one of the greatest military leaders in history. The company's logo references this fact, as it features two elephants in profile with a mountain peak, referencing Hannibal's crossing of the Alps with an army which included war elephants. 
The corporation is a powerhouse, multi-system corporation specializing in cutting edge technology and manufacturing, no matter the obstacles. Based in the city of Kotka, Pori on the planet New Carthage, Hannibal has always been at the frontier of integrating weapons systems and armors with the newest technologies available. Many of the company's exports are in fact, prototypes, and have not seen wide use outside of simulations such as Wargames. However, they produce some of the most well known materials in service with the UNSC. Hannibal is also responsible for crafting some of the most outrageous and exorbitantly expensive variants of the MJOLNIR power armor, and for good reason.
Its Aviator-class saw widespread use with Spartans acting as pilots for the GA-TL1 Longswords, YSS-1000 Sabres, F-41 Broadswords, and B-65 Shortsword bombers. The armor made it easier to interface with the aircraft's systems and created a comfortable environment for the pilot at high altitudes.  On the ground, Hannibal excelled at creating armor that shrugged off most of The Covenant's plasma weaponry during The Covenant war. The best example of this is the Rouge-class MJOLNIR variant. The 'Rogue' Armor saw limited use during The Covenant war, despite reports indicating its exceptional performance. Operators utilizing the armor reported they could remain combat viable for several days, despite taking several hits from large scale plasma weaponry.  A true testament to Hannibal's high standards of manufacturing. Recently, it has taken over production for the Viper-class MJOLNIR variant, which specializes in heightening aggression levels of the operator. The Viper-class is said to be almost inexcusably expensive, and due to its reputation for inducing "blood rage" within the operator, the UNSC is hesitant to place the armor into common circulation. However, with a few tweaks, the Viper-class has the potential to be a battle-changing piece of gear for the Spartans.
Perhaps their most important technology development, however, is that of the VISR system. Which is used by all Spartans and ODST personnel as an armor visor augmentation which carries a full battle suite heads up display. 
Post war, Hannibal has shifted its focus from practical products, to state-of-the-art technological breakthroughs. The company spent several years perfecting its combat exoskeleton the HRUNTING Mark III Cyclops, which saw use during the early stages of The Covenant war. Their continued research lead to the development of the HRUNTING/YGGDRASIL Mark IX, also knows as "The Mantis." The Mantis is a premier combat exoskeleton, protected by armor plating and energy shielding. Armed with lock-on rockets and a high speed gatling cannon, the Mantis is a versatile weapons platform capable of unmatched destruction and mobility. It has been exported is several variants, both military and civilian. 
After the AI Cortana swept through Human space with her fleet of Forerunner Guardians, Hannibal is assumed to have moved its manufacturing to an undisclosed location where it has begun working on weapon systems that can effectively deal with the Created threat.
Their solution? Massive and unmitigated experimental firepower.
Their first two breakthroughs are an upgraded Mantis combat chassis, which features hardened ablative armor, a rapid-fire gauss cannon, experimental ion field missile warheads which releases several sub-munitions, and the ability to create an EMP with a stomp attack. All of these systems are ideal in combating artificial threats, which are weak against electro-magnetic weaponry. The second, is their upgraded Scorpion main battle tank variant code-named the "XM820B4." It has been fitted with heavy armor and an incredibly powerful ion laser cannon capable of blasting clear through the armor of most Forerunner vehicles. The secondary gunner turret has been converted to the same rapid-fire guass turret in which the Hannibal Mantis employs.  These weapons platforms are currently undergoing testing within the Wargames combat simulator. Initial results are more than promising.
It is clear that if humanity is to survive the threat of The Created, it is essential to have Hannibal Weapons System's experience and technology behind it.
I hope you have found this briefing to be, enlightening. Hopefully you can now more appreciate the weapons, vehicles and armor systems you equip into battle.
Please refrain from damaging or neglecting your "products." They are not easily replaced.
A Halo fan since the beginning, 2001. Also a games industry consultant, writer, and educator. These are my thoughts, praise and advice concerning the past, present and future narrative of the Halo franchise.
Halo, all assets within, characters and merchandise are property of the Microsoft Corporation and is developed by its subsidiary 343 Industries.
I do not own, claim to own or retain any rights to the Halo franchise. This is a fan based work, and is strictly non-profit.
All other images, articles linked, materials and franchises that are not strictly specified as my own are property of their respective owners.
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