Combat skin

Combat Skin is a Forerunner term relating to body armor. The Forerunners had a classification system for combat skins, running from Class 1 to 18, and possibly above. According to 343 Guilty Spark, the Human MJOLNIR Mk.V Battle Armor is ranked on this scale as Class 2.

Armor of the Forerunner
Not much is known about Combat Skin. The term first comes up in the level Library, when 343 Guilty Spark wonders why John-117 had brought "such ineffective weapons" to combat the Flood. Guilty Spark recommends that the Chief upgrades from the MJOLNIR armor, which, according to a Forerunner ranking system of unknown criteria, is only Class 2(determining that the Forerunners were very advanced in combat armor). Guilty Spark notes that John's Mark V armor, is ill-suited to combat the Flood. He suggests that Master Chief upgrade to at least a Class 12 Combat Skin. It is technically possible that 343 Guilty Spark is unaware of the armor's full potential because perhaps he is not capable of scanning the entire armor system.

In at least one of the terminals in Halo 3, there is also an order that all Civilian personnel are required to wear at least a Class 8 combat skin unless inside the core areas, and all Military personnel are required to wear at least a Class 12 combat skin. John notes that if there is a suit six times as powerful as MJOLNIR, then he'd be the first to try it on.

This implies that the Forerunners made extensive use of armor, presumably powered armor, to the extent where there were possibly at least eighteen or more ranks of effectiveness or usability.

It is possible that the classes are not elevations of strength and durability of armor, but different types of armor for different purposes.

In the Halo trilogy by Eric Nylund and William C. Dietz, the Covenant were explained to have based much of their technology off of discovered Forerunner artifacts. Covenant Prophets adopted technology found in, or on Forerunner worlds or structures to meet their own needs. Now Covenant troops wear and use these Forerunner treasures throughout the Halo universe, though it should be noted that the MJOLNIR Mk V that John-117 wore in Halo CE was an upgraded version of Covenant shielding systems. The classification could mean that the higher the class the more possibilities or powers the skins possess.

What Does the Class System Mean?
Because so little is mentioned about combat skins, there is much speculation about exactly what the combat skin rating indicates. The obvious interpretation is that the combat skin ranking system measures raw power, and that a class 12 combat skin is 10 ranks higher in protection and power than a class 2, but if the Forerunner were able to use a suit at least six times more powerful than the Chief's, it's a wonder they had such trouble with the Flood, unless the Flood made use of such 'Combat Skin' themselves, such as an Elite Combat Form using a personal energy shield. This would mean that both forces would be equal in suit strength, as well as weapons and vehicles, while the Flood would most certainly outnumber the Forerunner. The most likely scenario is that in the Forerunner-Flood War,the flood infestation was billions of times larger in scale, which would mean that despite the Forerunner's near invincible armor, they may simply have been outnumbered.

Armor Class
Another interpretation is that the class system does not measure raw power, but rather classifies armor by it's role. Later in the game, as 343 Guilty Spark comments on the Flood's alteration of the atmosphere, he notes that "[The Master Chief's] Environment Suit should serve [him] well." This may indicate that Combat Skin with a Class 2 designation are designed for use as environment suits in hazardous terrain, rather than as effective armor to be used in combat against the Forerunner's enemies. There is a discrepancy to this assertion, however, as one of Halo 3's terminals makes mention of higher classes of Combat Skin that were vulnerable or ineffective against the Flood.

Environment/Combat Suit
Another theory states that a combat skin may also be an environment suit. A modern day analogy would be a HAZMAT suit, which is an environment suit, but has no further use in combat, while a suit of Kevlar provides physical protection but no environmental protection. John-117's "combat skin" also functions as an "environment suit"; this can overlap with other theories, as a useful environment suit may lack in either pure power or suitability for its role in combat. Quite possibly, John-117's "combat skin" may be half environmental and half battle armor.

Shielding Theory
A final theory states that "combat skin" does not refer to armor at all, but rather shielding; the disparity in power between the Master Chief's shields in comparison to that of the Forerunners is obvious. This is again compatible with either the power or role theory, as Class 12 shielding may be powerful enough to shrug off any Flood attack, or specifically designed to handle the damage from the Flood. Some have specified that if you raise your shield level to maximum in Halo 3's settings, you would have something close to a Class 12 Combat Skin, although this will never be known as correct or wrong since the actual power of the Class 12 Combat Skin has never been witnessed.

Trivia

 * It is possible that the scale counts down, rather than up. Proof of this can be found in the 4th Halo 3 Terminal. In one of the messages, it is required that "Combat personnel will only be permitted to wear [combat skin] rated below [class 8] in core areas, once operations begin." It doesn't make sense to require that only level 8 and worse combat skin is used. A reason for this could be that the higher classes were in short supply and were needed in combat areas so this limit could be to prevent high class combat suits being "wasted" in a safe area when they could be doing good in a combat situation. This may prove that either different numbers have different purposes, or that the scale is reverse, where 1 is the best and 18 is the worst, however this is unlikely because Guilty Spark says John should upgrade from class 2 to class 12.
 * The difference in nomenclature, has led some to believe that the two items 343 Guilty Spark refers to are different, i.e. armor is an "environment suit" and the body is the "combat skin."
 * 343 Guilty Spark mentions combat skin again in Halo 3. Sometimes if the player is killed he will say "I told you to upgrade your combat skin". Considering that 343 Guilty Spark says this when the character is killed by anything, Flood or otherwise, it can be assumed the class 2 Combat Skin isn't designed to protect only from attacks by the Flood.
 * Also, in conjunction with the above fact, it can be possible that, although John moved from Mark V to VI, in Forerunner terms, it is still a Class 2 suit.

Related Links

 * MJOLNIR armor
 * Semi-Powered Infiltration Armor
 * Elite Personal Energy Shield
 * Body Suit