- "There won't be any program; not like the Spartan-Twos, anyway or the Spartan-Threes, if I can help it. We're back to using consenting adults now, like we did in Project Orion."
- —Admiral Margaret Parangosky, CINCONI
The SPARTAN-IV Program is the fourth iteration of the SPARTAN supersoldier program. Like the original ORION Project, the SPARTAN-IV Program utilizes consenting adult volunteers selected from the other branches of the UNSC Defense Force, in contrast to the previous two programs which used children as candidates. Recruits are drawn from both career military veterans and young soldiers who show considerable promise. The SPARTAN-IVs serve in the wholly new Spartan branch of the Defense Force.
Commissioned as a result of the success of the preceding SPARTAN-II and SPARTAN-III projects, the SPARTAN-IV Program was originally conceived by Commander Musa-096, a former SPARTAN-II candidate who was crippled by the augmentation process. Despite his grudge toward Dr. Catherine Halsey and ONI, Musa recognized the crucial role of the Spartans in defending humanity and the continued importance of the supersoldiers in the aftermath of the Human-Covenant War. The proposal was approved by Admiral Margaret Parangosky, the former Commander-in-Chief of the Office of Naval Intelligence and the new program was initiated under her orders. Parangosky initially planned to have SPARTAN-III lead Colonel James Ackerson heading the program, with SPARTAN-II project lead Dr. Catherine Halsey to be reassigned as Ackerson's subordinate. Ackerson was killed following the Battle of Mare Erythraeum and Halsey was arrested after returning from Onyx, though ONI continued the program without the two, with the help of Musa and Jun-A266, a former SPARTAN-III Alpha Company member.
In addition to the significant numbers of adult volunteers which make up the majority of the SPARTAN-IVs, the SPARTAN-IIs and SPARTAN-IIIs who survived the Human-Covenant War were offered to be integrated into the SPARTAN-IV Program. The first class of SPARTAN-IVs went active in early 2553. Hundreds of SPARTAN-IVs are assigned to the UNSC Infinity, the most powerful warship ever constructed by mankind. They train with one another in simulations known as "War Games" on the Infinity's state-of-the art combat deck (a training chamber that is capable of replicating environments), in order to constantly stay battle-ready.
The SPARTAN-IVs serve in a dedicated branch of the UNSCDF known simply as "Spartan", whereas their forebears operated within other chains of command. Unlike their predecessors, the SPARTAN-IVs are identified by their surnames rather than numeric tags (due to their volunteered enlistment rather than kidnapping/conscription). Unusually, the SPARTAN-IVs have shown a great deal of solidarity, especially impressive given the short time they have served together. Many of them have adopted colloquialisms first used by the SPARTAN-IIs, such as "Alpha Bravo" for "Alien Bastard". Psychologists assert that this camaraderie and cohesiveness will help distinguish the SPARTAN-IVs, and the Spartan branch as a whole, from the other UNSCDF branches.
 List of Spartan-IV units
|UNSC Infinity Spartan command||Active|
|Gypsy Company||Active||At least two Spartan-IVs||Also contains UNSC Marine Corps personnel.|
|Mountain Squad||KIA||A science attache unit. Killed during the Requiem campaign after being shot down in Two Giants.|
|Fireteam Apex||Active||unknown||Participated in the Requiem campaign|
|Fireteam Avalanche||Active||unknown||Participated in the Requiem campaign|
|Fireteam Bailey||Unknown||unknown||Participated in the Battle of Ealen IV|
|Fireteam Castle||KIA||Killed in action after being shot down during the Requiem campaign|
|Fireteam Crimson||Active||Four Spartans|
|Fireteam Domino||Active||unknown||Participated in the Requiem campaign|
|Fireteam Forest||Active||Aided Crimson in acquiring replace power supply for the Harvester|
|Fireteam Horse||Active||unknown||Participated in the Requiem campaign|
|Fireteam Ivy||Active||unknown||Participated in the Requiem campaign|
|Fireteam Jackknife||Active||Participated in the Battle of Ealen IV|
|Fireteam Kodiak||Active||unknown||Participated in the Requiem campaign|
|Fireteam Lancer||Active||Participated in the Requiem campaign|
|Fireteam Majestic||Active||Participated in the Requiem campaign and the Battle of Ealen IV|
|Fireteam Rhino||Active||unknown||Participated in the Requiem campaign|
|Fireteam Shadow||Active||Participated in the Requiem campaign|
|Fireteam Sword||Active||unknown||Participated in the Requiem campaign|
|Fireteam Switchback||Active||Captured during a mission to destroy a Harvester during the Requiem campaign Later rescued by Fireteam Crimson and Fireteam Lancer.|
|Fireteam Sydney||Active||unknown||Participated in the Requiem campaign|
|Fireteam Talon||Active||unknown||Participated in the Requiem campaign|
|Fireteam Tower||Active||unknown||Participated in the Requiem campaign|
|Fireteam Wolf||Active||unknown||Participated in the Requiem campaign|
- Edward Davis KIA
- Gamma Company
- Several SPARTAN-IV killed by Gek 'Lhar
- Joel Thomas
- Yeong-hao Holst
Ten SPARTAN-IV candidates were discharged from the prototypic phase of the program after being crippled or killed by the augmentations.
- Ilsa Zane - Discharged after her augmentations left her mentally unstable. Assigned to the Office of Naval Intelligence, but subsequently escaped and defected to the Insurrection.
 MJOLNIR armor
- Main article: MJOLNIR Powered Assault Armor (GEN2)
SPARTAN-IVs are equipped with the MJOLNIR [GEN2], the second-generation version of the MJOLNIR Powered Assault Armor. The standard-issue armor set for Spartan-IVs is the Recruit variant, colored gray and orange. An assortment of armor configurations are available for all new Spartans per UNSC Regulation 3A-950, and Spartans are capable of customizing their individual armor set with modular components from a wide range of special-purpose variants, based on their personal preferences, specialization and mission requirements. Unlike the uniformly green coloration of the SPARTAN-IIs' first-generation MJOLNIR armor, SPARTAN-IV armor comes in a profusion of distinct color patterns, with the members of specific teams often sporting a consistent coloration.
 Augmentation procedures
Like the augmentations performed for the SPARTAN-IIs and the improved procedures utilized in the subsequent SPARTAN-III Program, the SPARTAN-IVs underwent a series of procedures to enhance their physical capabilities and to wear MJOLNIR armor. Unlike the Spartan-III augmentations, which consisted solely of chemical injections, the SPARTAN-IV augmentations combine chemicals and surgical procedures like those pioneered by Dr. Catherine Halsey in the SPARTAN-II Program. The technology used in the two preceding SPARTAN programs necessitated that the candidates meet exceedingly strict genetic qualifications as well as the application of the enhancements on preteens, to avoid the catastrophic failure rates produced by the augmentation of adult subjects in the ORION Project. By the time of the initiation of the SPARTAN-IV Program, the technology had advanced to the point that adults could be augmented seemingly without major risk.
The SPARTAN-IV augmentation procedures take three weeks to perform. While the enhancements have not been described in detail, they incorporate technologies originating from prior SPARTAN programs as well as completely new additions:
- Bones are infused with a substance that makes them nearly unbreakable.
- Muscles are injected with a material that allows them to work harder without breaking the subject's skeleton.
- Corneal implants are provided to improve night vision.
- Heart is implanted with a synthetic weave which significantly increases its capacity to pump blood, allegedly allowing a SPARTAN-IV to "outrun a horse".
- Lungs are lined with a polymer that enhances oxygen intake and allows them to process toxins or foreign gas mixtures, potentially allowing a SPARTAN-IV to breathe methane for around an hour.
- Intestinal bacteria are altered to enable the digestive system to absorb more nutrients out of food.
- Pancreas is replaced by a completely new, vat-grown organ.
- Blood is altered to allow for faster clotting.
- Subject is given several implants to help medical teams keep tabs on them.
A series of additional augmentations were included in the earliest, prototypical phase of the program. While these enhancements would have made the Spartans significantly stronger and more resistant to injury, they proved to have an unacceptable casualty rate, killing or crippling nine of the ten initial candidates while leaving the sole survivor mentally unstable.
A SPARTAN-IV from Making Halo 4: First Look.
 List of appearances
- Halo: Glasslands (First mentioned)
- Halo: The Thursday War (Mentioned only)
- Halo 4 (First appearance)
- Halo: Spartan Assault
- Halo: Initiation
- Halo: Escalation
- ^ a b YouTube: Halo 4 Flag Stabbing and Spartan Cosplay - Comic-Con 2012
- ^ a b Halo: Glasslands, page 434
- ^ a b Eleventh Hour reports, part 3
- ^ a b c Halo 4 Official Site: Story
- ^ a b c Halo: Initiation, Issue 1
- ^ Halo: Glasslands, page 147
- ^ a b Halo: Glasslands, page 422
- ^ Halo: Glasslands, page 435
- ^ a b Gameinformer (May 2012), pages 46-47
- ^ a b YouTube - Halo 4: Spartan Ops Gameplay
- ^ a b Halo 4, level Reclaimer
- ^ a b c d Spartan Ops, S1E3 Spartan Mountain
- ^ a b c d e f g h i j k l m n o p q r Halo 4 Limited Edition — War Games Session Summary
- ^ Spartan Ops, Episode 7, Chapter 2: "Home Field"
- ^ Spartan Ops, S1E1 Departure
- ^ Spartan Ops, S1E4 Didact's Hand: Chapter 1: Hairy Call
- ^ Spartan Ops, Episode 10, Chapter 3: "Seize the Power"
- ^ Spartan Ops, Episode 7, Chapter 4: "The Guns of Infinity"
- ^ MightyApe.co.nz: Halo 4 Limited Edition screenshots
- ^ YouTube - Halo 4: Spartan Ops - Episode 6 Chapter 4 Developer Commentary
- ^ Spartan Ops, S1E8 Expendable: Chapter 3: Lancer
- ^ a b c Halo: Initiation, Issue 3
- ^ Halo 4, Recruit armor description
- ^ Halo 4 campaign level Infinity
- ^ a b Spartan Ops
- ^ Halo 4 Limited Edition - Infinity Briefing Packet
- ^ Dr. Halsey's personal journal
- ^ a b Halo: Initiation, Issue #2