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.

M52 Combatant Protective Equipment System
The M52 was a 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 Due to its success, it was iterated upon and produced well into the 26th century until being superseded by the M43 UCES in the 2540s. 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. Some of the most notable of these are the M52A and M52B body armors, which retain the same base design but were manufactured by different contractors decades apart, and the ubiquitous CH252 combat helmet.

(Halo 2 / Halo 3 design)

M12 Enhanced Protective Equipment System
A heavy armor set developed in response to the escalating threat of the Insurrection, the M12 plating ensemble never became as widely-adopted as the then-standard M52-derived systems. 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. 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 M12's existing issues with heavy weight persisted, and the suits gained a reputation as being more of a hindrance than help as plasma hits would melt the heavy plating, originally designed to protect from ballistic attacks, and at worst hinder the provision of first aid. 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 standard.

(Halo Wars / Halo 2 Anniversary design)

M43 Universal Combatant Equipment System
The M43 was the UNSC's most ambitious standardization push yet, with the new standard being applied UNSC-wide due to the increasing logistical challenges of keeping up with the Covenant and arming units fast. The M43 standard included a redesigned combat uniform, now fully vacuum-compatible, and thermal-resistant underlayers to limit damage from plasma strikes. Equally significant was the push to standardize armor and load-bearing equipment to be cross-compatible between various systems. Most new systems produced since the M43's unveiling would be compliant with the standard (including the formerly-specific MJOLNIR armor), though conflicting standards remained in use all the way to the end of the century.

(Reach design)

M43-compliant up-armor kit. Cumbersome appearance is due to the use of rudimentary proto-shields under the plating. (Halo CE design)
 * M50 Heavy Blast Plating