UNSC infantry combat ensemble

The combat ensemble is the collection of equipment worn by individual UNSC infantrymen. The ensemble consists of various layers of fabric combat uniform or battledress, protective equipment typically including at least a form of body armor and a helmet, load-bearing equipment, as well as various electronics and other performance-enhancing gear.

Historically, the different branches of the UNSC armed forces have used unique forms of battledress and protective gear, though attempts at cross-branch standardization have been made; the most common of these being the frequent asset sharing between the UNSC Army and Aerospace Force, while the UNSC Marine Corps have historically fielded their own gear.

Battledress
The battledress, field uniform, or combat uniform serves as the base layer of the ensemble. For most situations, the battledress takes the form of fabric-based fatigues along with a system of undergarments. Specific variants or additional clothing is used for missions in different environments, such as arctic or desert-based operations. Field uniforms come in camouflage appropriate to the environment. By the mid-26th century, combat fatigues can be woven of smart fibers capable of altering their camouflage pattern based on a set of pre-programmed patterns. Due to their expense, however, such variable-camouflage uniforms are only issued to units that regularly fight in highly varied environments.

All branches issue separate combat suits for use in a vacuum, prolonged EVA combat, as well as environments with ambient hazards, though such suits are produced and requisitioned in more limited numbers due to their specialized nature. These specialist combat suits are usually designed to be at least partly compatible with the armor plates and gear systems of the surface-based sets, and the trend has been toward further integrating the two; the UCES standard and the M43 WES represent the latest development in this, with plate systems and even certain electronics mostly intercompatible with the corresponding EVA suits.

Armor
Most types of standard-issue UNSC protective equipment include a form of armor-plated body armor and a helmet at their core. The body armor is usually a two-piece design, with a plate carrier to cover the chest and back, and an armored belt encircling the abdominal area; some versions eschew the latter. Some designs incorporate a padded protective vest under the plate armor; the chest and abdominal plates may also be designed to be secured to this vest. Many body armor designs incorporate optional extensions to protect the groin and hips. These are often supplemented by armor for the shoulders, forearms, lower legs and sometimes the thighs, as modern forms of armor plating are lightweight enough to make such coverage viable whilst not critically weighing down the combatant.

Equipment
UNSC combatants are issued a suite of personal equipment based on their specialization and mission requirements. At its core, the equipment of an individual warfighter has changed little over the centuries, although specific technologies have improved.

Equipment system standards
The following lists major shifts in UNSC infantry ensembles, or "equipment systems". These are overarching generations or patterns of equipment designed around the same time to be part of a cohesive whole. Such equipment systems usually include most, sometimes all, components of a combatant's ensemble: combat fatigues along with possible underlayers and accessories, armor plating and protective gear, webbing and load-bearing equipment as well as an array of electronics and even external equipment such as Jogger Frames. Until the M43, these have typically been specific to select branches.

Ideally, an individual infantryman's ensemble would consist of gear belonging to a single pattern, though this is not always the reality in the field. Notably, the different generations of equipment system are often at least partially inter-operable in terms of individual components; for example, a mostly M52-based ensemble might be complemented with M12 greaves and cuisses for urban theaters or boarding actions. Due to logistical realities, many units and even individual combatants within those units would often field a variety of gear from different sources; this became particularly pronounced during the Human-Covenant War as units moved rapidly from system to system and the remaining personnel of largely devastated units were merged into other units. Even single companies might end up as a hodgepodge of equipment, some of it scavenged from the fallen to replace broken, defective or simply missing gear.

M86 Protective Equipment System
The now-archaic predecessor to the M52 CPES, deployed since the late Inner Colony Wars through to the early years of the Insurrection.

M52 Combatant Equipment System
The M52 was a branch-wide equipment standard shared by the UNSC Marine Corps and the Navy, originally launched in the 2450s. Due to its success, it was iterated upon and produced well into the 26th century until being superseded by the M35 and M43 ensembles. As the M52-based kits were manufactured for nearly a century, some variety naturally crept into the series- though none of this variety was enough to qualify the newer iterations as a new standard as the systems were based on the same core architecture. Some of the most notable of these are the M52 series of body armors, which retain the same base design but were manufactured by different contractors decades apart, and the CH252 combat helmet.

M12 Enhanced Protective Equipment System
The M12 Enhanced Protective Equipment System was a supplemental plate kit based on the M52 combat ensemble and usually utilizing the same battledress. A set of enhanced armor requisitioned by the UNSC Marine Corps in response to the escalating threat of the Insurrection, the M12 encompassed fully-armored cuisses, pauldrons, vambraces and greaves, in contrast to the more lightly-armored M52. Over the course of the Insurrection, the M12 was deployed as a heavy plating set (fully or partially) in MOUT and boarding actions in particular. In such roles the M43 was highly successful, providing best-in-class ballistic protection against many forms of small arms fire despite its heavy weight and reported issues with ergonomics. However, the M12 plating never became as widely-adopted as the then-standard M52 personal armor kit.

After the onset of the Covenant War, the Marine Corps experimented with using the M12-based heavy armor against the Covenant due to its superior armor coverage, with some frontline units being issued with prototype refractive coatings. While these suits enjoyed some success, the ceramic-alloy layers in the heavy plating were originally formulated to stop ballistics and blast fragments, and were poorly optimized to insulate from plasma and radiant heat. The plates could actually retain the heat from a direct hit, and sometimes hindered the provision of first aid. As a result, the M12 heavy plating gained a reputation as being more of a hindrance than help. Marines in theaters such as Harvest were even reported as deliberately discarding (or "losing") much of the heavy plating for increased mobility. Manufacture of the M12 system was halted indefinitely in 2533 as the UNSC began drafting a dedicated armor system to use against the Covenant- one that would become the M43 WES.

As frontline units upgraded to the new M43 WES, most suits of M12 EPES were surplused and sold to colonial militias and private military contractors.

Universal Combatant Equipment System
The Universal Combatant Equipment System (UCES) is the UNSC Armed Forces' latest and most successful attempt at standardizing gear between different branches and units, enabling intercompatibility between various disparate forms of combat ensemble. While the basic idea of a cross-branch equipment had existed for decades if not centuries, the frantic pace of the Human-Covenant War and the ensuing logistical challenges of supplying frontline units put pressure on the UNSC and forced them to seriously contemplate its implementation. The UCES was conceived as an overarching standard imposed on manufacturers to make numerous disparate armor and equipment systems inter-operable. Though some of this cross-compatibility had existed in prior generations within the various branches, its adoption among contractors was limited. Still, the UCES standard would not be an entirely fresh start but instead accommodate several existing systems already in service, including some of the armor and webbing of the latter generations of the M52 pattern.

Most types of protective gear and load-carrying equipment produced since 2540 have been compliant with the UCES standard (including the formerly-specific MJOLNIR armor), though conflicting standards remained in use all the way to the end of the century.

M35 Equipment System
A redesigned form of combat armor, the M35 was the Marine Corps' first response to the Covenant threat. Largely derived from the tried-and-true M52 plating architecture albeit with the upcoming UCES standard in mind, the M35 incorporated new forms of ablative ceramic armor designed to better counter the Covenant's plasma weapons. Since its introduction in the 2530s, the M35 became standard-issue for most Marine units for the rest of the Human-Covenant War. M35 systems were a common fixture of Marine units on Earth and the Inner Colonies well into the late 26th century, even with the branch-wide shift to the M43 standard. Many components of the M35 armor and webbing are UCES-compliant and backwards-compatible with the M43, which allowed the Marine Corps to use the two systems back-to-back for decades. Some suspected that the Marines' reluctance to shift to the M43 standard had to do with their inter-service rivalry with the Army, which had spearheaded the M43 project, with some members of the Marine brass having been left dissatisfied with some of the corners cut in the development of the M43. As well, numerous units of the M35 had already been built, with dedicated assembly lines established on Mars and Tribute.

M38 ODST assault armor
The M38 assault armor is the most recent iteration of the ODST combat ensemble, designed in conjunction with the UCES standard and thus ensuring cross-compatibility between standard infantry and special forces equipment loadouts. Many early features of the nascent M43 were initially field-tested by ODST forces throughout the 2530s, informing design principles for the final production runs of both programs. This resulted in the development of the M38 ODST combat armor, which quickly surpassed prior systems due to its superior protection and modular features. However, earlier systems remained in various secondary uses, such as the M09 ODST ensemble, which was issued to reconnaissance units as late as the mid-2550s due to its lighter weight.

Like the M43 WES ensembles, the M38 ODST armor has a modular vacuum-rating system. The external armor plating can be worn either with a basic underlayer designed for surface combat, or a fully-pressurized techsuit intended for operations in a vacuum. For primarily space-based missions, however, ODST Space Assault units field separate combat suits specifically designed for EVA.

M43 Warfighter Equipment System
The M43 is an all-in-one equipment system, encompassing cross-compatible combat ensembles for all the UNSC's branches as part of the UCES push. A project driven by the UNSC Army and Aerospace Force to replace their aging and inconsistent systems, the M43 pattern was built on top of years of learnings from encounters with the Covenant. As a major inter-service push, the M43's development was filled with controversies and differences of opinion over the supposed role and features of the next-generation combat ensemble. Eschewing some of the specialization of the older systems was a common concern, though the voices pushing for modularity and standardization eventually won out. In development for over a decade, the process was delayed several times by these troubles along with difficulties involving finding suitable manufacturers. Ultimately, HIGHCOM was responsible for moderating the process and eventually hammering out the decisions that led to the M43's development.

The M43 standard included a complete overhaul of the battledress, beginning with the underlayers. A thermal-management skinsuit was made a staple part of the ensemble, along with new combat fatigues expressly designed to be resistant to plasma damage. The M43 skinsuit is a technical undergarment woven of a reactive smart cloth designed for maximum heat dispersal, keeping the wearer cool both under exertion and in hot climates, as well as actively minimizing radiant heat from glancing plasma blasts.

The ensemble also includes an optional pressurized layer for survival and short-term operation in exoatmospheric environments; this is an advanced form of mechanical counterpressure suit meant to be worn under the fatigues. The design was based on prior "tightsuits", or low-profile, form-fitting vacuum suits conventionally used by special forces, which became increasingly common in the 25th century due to materials advances pioneered by programs such as MJOLNIR and were now finally regarded as viable for mass adoption. Surface-based forces eschew the vacuum-enabled layer, as it is much more difficult to don and remove and will become uncomfortable when worn over prolonged periods of time. Still, the limited vacuum capability was a significant change from prior systems; while this meant higher costs for individual suits, it also cut costs from the logistics of having to produce separate surface-based combat and brief exoatmospheric incursions. For prolonged vacuum-based combat, a dedicated M43-based EVA fighting suit line was released several years later, based on lessons learned in the development of the M38 ODST armor and related systems. Meanwhile, the HAZOP variant of the ensemble is designed for actively hostile environments such as extremes of temperature or pressure.

The M43-generation armor plating uses new alloys and layered titanium composites piloted by the ODSTs and other special forces. These are a form of ablative armor designed to break off when hit by plasma strikes, rather than melting or heating up like earlier forms of armor.

The M43 also features an overhauled electronics and battlefield awareness suite embedded within the ensemble's bespoke CH43 or ECH43 combat helmet.

The M43-pattern combat ensemble was introduced into service in the Army and Aerospace Force starting in 2545, first issued to units on Reach and other key Inner Colonies. The Marine Corps adopted the M43 standard in 2547, mainly in expeditionary units, while many units based on Earth and the Inner Colonies would retain M52-pattern legacy gear for decades, only upgrading to M43 derivatives as the remaining M35 ensembles broke down with use and eventually became obsolete due to technological advances.

M49 Heavy Blast Plating
M43-compliant up-armor kit first launched within the Marine Corps, designed with similar operational goals as the earlier M12 EPES but with plating optimized against energy weapons. Designed to be compatible with the M43, M49 plating features enhanced chest armor, shoulders, thigh plating and armored tassets, as well as armored gauntlets similar to the M12. The M49 uses a form of energized plating with rudimentary proto-shields embedded, giving it a somewhat bulky appearance. While nowhere near the effectiveness of true energy shields, the proto-shielded plating acts as a localized form of reactive armor intended to reduce the energy of incoming plasma strikes.

First introduced in specific units such as the battalions selected for Operation: RED FLAG, M49-based plating systems would become more commonplace in the post-war years.

Behind the scenes
The gear we see in the games is meant to be as follows:


 * Halo: Combat Evolved: M43-pattern fatigues and kit with M49 Heavy Blast Plating and CH43B helmet. The decision to have the oldest and arguably most archaic-looking armor set in the series be the most recent one may be weird. However, it wasn't an arbitrary one. The Pillar of Autumn was chosen for Operation: RED FLAG, so it doesn't make a great deal of sense that the Marines on board would be issued the oldest gear the UNSC has; stragglers the Autumn picked up from Reach certainly might, but if we go by Halo CE visuals, we can assume that the set was worn by the majority of the Marines on the Autumn. Instead of retconning the entire set out of existence (like Halo: CEA did), we assume some artistic license applies to the depiction in Combat Evolved; namely, the plating and underlayers would have a more detailed appearance similar to that in Reach, whilst following the general forms shown in Combat Evolved. We actually see hints of this in some of Isaac Hannaford's concepts for Reach, and while the final Reach set worn by the Marines accompanying Keyes in Reach certainly evokes the CE design, we believe we can do better and say that the CE-style plate configuration exists alongside (and complementary to) the Reach one.
 * Halo 2: M52B-based armor set and a CH252 helmet.
 * Halo 3: M35-based combat fatigues and armor set with an ACH/CH34 helmet.
 * Halo Wars: M52-based combat fatigues with M12 EPES and CH10 helmet
 * Halo: Reach: Various M43-based ensembles, the helmet being the accompanying CH43 or ECH43.