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"SIGMA gives us a chance to field SPARTAN soldiers in a variety of top secret roles that their peers on Reach could never be used for. We are all aware of the controversy surrounding the SPARTAN-II Program's progenitor, particularly regarding her methodology and attitude. As such, I will take it upon myself to direct this splinter project so they may act as the Office of Naval Intelligence's top field operatives, while retaining the same assets that benefit the other candidates for this much-needed program."
Calvin Roe, proposing SIGMA to ONI's Section Three.

Established in the early 26th Century, Project SIGMA was a little-known offshoot of the highly controversial SPARTAN-II Program. Established with many similar structures to its parent program, SIGMA featured a smaller number of recruits and was designed to create powerful supersoldiers that would serve the Office of Naval Intelligence alone. After the arrival of the Covenant meant that most of SIGMA's augmentees would be assigned to fight the alien threat, the Spartans spent decades fighting both on the frontlines and as part of numerous classified operations. While few survived the war and the project was ultimately shut down, SIGMA was responsible for producing some of the finest supersoldiers of its era.


In 2517, the highly secretive SPARTAN-II Program was approved by HIGHCOM and the Office of Naval Intelligence. The project would entail the kidnapping of young children from across the colonies and subjecting them to an intense regimen of training and conditioning to become humanity's finest soldiers. While SPARTAN-II was originally the brainchild of the brilliant but unorthodox Doctor Catherine Halsey, SIGMA emerged shortly afterwards as a secretive parallel program, to be conducted without her knowledge. This was done for a multitude of reasons, ranging from mistrust of Halsey to the fact that certain high ranking intelligence officers wished to have these soldiers personally assigned to them for secret missions. The man who came forward with this plan was Doctor Calvin Roe, an esteemed civilian consultant for ONI who became famous for his work in powered armour and robotics, much of which was later incorporated into the iconic MJOLNIR armour suits that served the SPARTAN-II soldiers for decades. Roe had initially been informed of SPARTAN-II by Frederick King, an ONI agent who prompted him to propose the idea of a secondary group to both Margaret Parangosky and the head of Section Three. Deliberately playing off Parangosky's dislike of Halsey, King and Roe were able to get SIGMA approved before the former returned to his work as head of the BRUTUS division, leaving Roe to manage the project as funding was diverted and facilities were created on Earth.

For SIGMA, only twenty candidates would be selected for training, a much smaller size than the 75 chosen by Halsey. Though this would still leave over fifty potential SPARTAN trainees out there, Roe reasoned that with a smaller group more improvements could be made to each individual member, making them extremely efficient in and out of combat. As with Halsey's group, funding was also an issue, contributing to the much smaller scale of the SIGMA project. In addition to those chosen from the rejected group of SPARTAN-II candidates, a few SIGMA recruits were discovered shortly after the initial colony-wide sweep for potentials for the program; they were seen as too valuable to slip by, while the other prospective recruits had already been marked out entirely by Catherine Halsey before SIGMA was created. It was decided that the trainees could not be sent to Reach, as their chance of discovery by Halsey would be too great. Instead, the twenty recruits were secretly transported to Earth, the captial of the UEG and UNSC, for their training. To act as the chief instructor for the SIGMA group, Richard Mack Senior, a semi-retired special forces hero and former ORION operative, was chosen after being personally recommended by both Calvin Roe and Admiral Margaret O. Parangosky, who had worked closely with him years before.

First-Generation SIGMA

In late 2517, all twenty of the specially selected candidates for SIGMA were abducted by ONI agents, being replaced by flash clones, who would quickly fall ill and die. They were then transported to a top-secret training facility in the United Republic of North America on Earth, where they would meet their trainers for the first time. Calvin Roe would work as the chief overseer of SIGMA, with Mack Senior as both the chief trainer and evaluator of these trainees. A single 'dumb' AI, Leonard, was also brought in to educate the children in military tactics. Due to the highly controversial nature of the project, which broke major laws, all people affiliated with the project were sworn to secrecy and largely confined to the facility, though Mack was allowed to leave periodically, living nearby. That aside, most members of staff were to live there for almost a decade, according to the projected training time for the average SPARTAN-II candidate by ONI. As the SIGMA Facility was classified as a 'black site' by ONI and did not officially exist, the staff and trainers working there were heavily monitored to ensure that no information was released; there were several incidents in which potential whistleblowers were discovered and quickly terminated by agents.

In terms of training, a secure line of information was set up from Reach to Earth, allowing SIGMA to make use of Halsey's notes and schedules for her group, in addition to their own initiatives. This was done successfully by ONI, under the pretence of having to keep track of the SPARTAN-II's training. Roe quickly noticed that Halsey was becoming oddly attached to her trainees, and, seeing this as highly unprofessional considering what they were doing to these children, made an effort to distance himself somewhat from the ones in SIGMA, allowing Mack, as a longtime soldier, to act as more of a father figure to the Spartans. After some initial difficulties, every single one of the SIGMA trainees began to show their true potential, a hierarchy quickly being established in terms of sheer ability, the specialities that each SPARTAN possessed in a certain field coming into light within a year.

Sigma Training Leaderboard

The leaderboard upon the first day of its implementation.

In early 2520, Roe made the decision to implement a 'leaderboard' for the trainees. This would rank each SPARTAN based on their combat performance during training sessions, designed to provoke some deal of competition and give them something to strive for. Though generally successful, several of the trainees became obsessed with attaining a high position in the leaderboard, several injuries occurring due to this. Chief among these was Jack-085, who was reprimanded on several occasions for excessive force against his comrades. The consistently top-performing member of the SIGMA project was Fenn-145, who remained there for the entire duration of their training.

It was in the early 2520s that the decision was made to split SIGMA into several groups upon the completion of their then-experimental augmentation procedures. This was approved by HIGHCOM, though Mack disagreed with it, believing that it would be better for each and every SPARTAN to remain together in the years to come. In addition, the largest group, Sigma-Alpha, would be told that their comrades perished during augmentations, allowing for a complete cover up on the other nine's files. Alpha, the largest group, consisting of eleven members, would be deployed on counter-rebel operations across the colonies, acting in areas where the other SPARTAN-II's could not. Beta, consisting of three members, would function as an intelligence-gathering team permanently assigned to a UNSC prowler for discreet missions. Gamma, which was made up of five members, would fill a role similar to Alpha's, but on smaller missions that required a greater deal of discretion, such as capturing high-value individuals or recovering specific objects.

In 2525, however, SIGMA was to undergo rapid changes, the project goals being greatly expanded in scope. The Covenant, a conglomeration of alien races, had attacked the colony world of Harvest, killing tens of thousands there. Later that year, Biko and several other Outer Colony worlds were assaulted and 'glassed' by these aggressors. With this new, massive threat to humanity as a whole, HIGHCOM ordered their training to be accelerated to the final stage: a series of physical, biological and chemical augmentations which would greatly enhance the subjects into true SPARTAN soldiers. As Halsey's group had underwent their own augmentations two months before, with over half 'washing out' of the program at this stage, ONI was able to greatly upgrade the procedures and correct prior mistakes. reducing the 56% casualty rate to a relatively low 14% in such a short period of time. In late May, the SIGMA Spartans went for their own augmentations aboard the UNSC Hopeful, and by what was considered a miracle by some, all survived without any deaths or debilitating injuries despite some heavy scarring in some augmentees. Though their number of twenty was still lower than the thirty-three survivors of Halsey's SPARTAN-II's, SIGMA was considered to be an unprecedented success.

Immediately following their augmentation procedures, nine SIGMA members, who would make up Sigma-Beta, Gamma and Gamma, were taken away from the facility, being assigned to separate bases on Luna, Mars, and the UNSC Point of no Return respectively. The sole 'washout' of the entire group, Derek-142, was kept aboard a medical station to recuperate from his injuries, and would eventually go through the augmentation process several more times until it was sucessful. The other eleven members would, as it had been decided by HIGHCOM, be sent out on missions against the Covenant, leaving counter-insurgency operations to Sigma-Gamma. The group spent several weeks recovering from their augmentations on the UNSC Hopeful before being transported back to Earth. It was not long after this happened that a breakout occurred in the SIGMA facility, leaving dozens dead. SPARTAN Jack-085, one of the best-performing trainees in the program, along with Ahmad-126, killed several guards, evaded Leonard and attempted to escape. This came as a great shock to Roe, who had believed that the intense mental conditioning that the SPARTAN's received would make them unshakeably loyal to their superiors and the UNSC in general. The pair slaughtered their way towards the hangar bay, trapping SPARTAN-133 and SPARTAN-041 as they attempted to stop them. They later encountered SPARTAN-035, who allowed them to pass but refused to join them, much to Jack's dismay. 035 was later questioned for his actions, but never charged for what was seen as a severe lapse in judgement.

With fears of Jack and Ahmad possibly recruiting more Spartans to their cause, Roe sealed off the facility barracks, where five of the others were at the time. Though this momentarily halted their progress, the escapees kept going, and were confronted by Richard Mack Senior. Though the veteran soldier was able to almost convince the pair to give up, a fight broke out, Mack holding his own for some time before being captured as four of the other Spartans arrived, forcing Jack to release him to escape. The pair left the facility via Pelican, initiating a week-long manhunt. Ahmad was found dead on the outskirts of a nearby city, having apparently committed suicide[1]. Jack disappeared, and in spite of all commercial flights from the city being thoroughly searched for the next few weeks, he was never found. Though ONI dispatched agents to search for the rogue SPARTAN, he proved near-impossible to locate; the young man's superb skills proved handy in avoiding not only his pursuers but the colony-wide surveillance grid as he fled Earth.

With this unfortunate mishap befalling SIGMA, Mack Senior departed the facility after a speech to his trainees, having been called back to serve as a military commander against the Covenant, along with many retired veterans, such as Preston Cole. Over the next couple of months, Sigma-Alpha received their experimental MJOLNIR Mark IV armour, training to efficiently use the suits for some time before finally being dispatched on a 'trial run' against an insurrectionist siege the next year. The other SIGMA teams were put through essentially the same process, though immediately after his reassignment the records of Derek-142 ceased to exist; Roe and the other project staff were unable to track him afterwards. The first mission undergone by the SPARTAN-II's was classed as a great success, with no casualties and all mission objectives being successfully completed by the nine members of Sigma-Alpha. Shortly after this, word came down to SIGMA that their operators were finally ready for deployment against the Covenant.

Marco Early War

SPARTAN-035 and SPARTAN-133 in 2526

With the SPARTAN-II's officially under the command of ONI and the UNSC Navy, Roe was assigned to MJOLNIR armour development, working to improve from the original models produced, making them more efficient for combat use. SIGMA operated efficiently over the years, Alpha being deployed against the Covenant on Brennus in 2530 after several years of counter-insurrection operations. Over the years, they were often used for field testing of MJOLNIR variants, such as CQB, EOD and SECURITY, making the most of them in combat and determining if they were to be mass-produced. In their many years of war, the SIGMA Spartans did not encounter the Reach-trained ones at all, nor was their presence ever detected by Catherine Halsey, largely due to a dedicated group of ONI agents covering their tracks and ensuring that SPARTAN-II deployment was coordinated to prevent any accidental meetings, which would uncover SIGMA's secrecy.

Over the years, very few could deny the extreme efficiency of both SPARTAN-II and it's subsidiaries, including SIGMA and others. Many victories were won and disasters averted due to the actions of these soldiers in the field, this level of success, unparalleled by any special forces unit before in history, justified the near-astronomical costs for constant armour requisitions, namely upgrades or occasionally, new suits. SIGMA did, towards the latter half of the war, begin to sustain casualties. During the Battle of Schönheit in 2545, SPARTAN-127 and SPARTAN-136 were declared MIA, in accordance with ONI's Directive 930, which declared that no SPARTAN-II asset could be declared as Killed in Action, for reasons of keeping up morale. In 2548 came the biggest loss of SPARTAN-II assets in the war, with every member of Sigma-Gamma disappearing during the Battle of New Oslo after the activation of an unknown alien artefact. Again, there were no confirmed deaths and a great deal of ambiguity as to where they had ended up, something that led to the incident becoming highly classified, but it still denied the UNSC five crucial assets in the future.[2]

Jack 2534

Jack-085 would re-emerge as an Insurrectionist leader in 2550.

The final two years of the war saw the fighting increase to an unprecedented level as SPARTAN-II assets were thrown into combat again and again with mounting casualties. Operation: SWEEPOUT in 2550 saw two more Sigma Spartans die as the rogue SPARTAN-085 engaged the UNSC in battle, but it was the conclusive year of the Human-Covenant War that proved to be the most devastating. Two members of Sigma-Alpha, along with Richard Mack Senior, were killed during the Battle of Harpa in March, with the others barely escaping. SPARTAN-063 was killed in July, his body being the only one recovered by his team mates. It was during the Fall of Reach, the biggest battle of the war, however, that saw the most extensive SPARTAN deployments, and deaths. Only one member of Sigma-Alpha was killed, though there were excessive casualties among other SPARTAN-II and SPARTAN-III assets defending the colony world. In addition, the founder of the SIGMA Project, Calvin Roe, was among the millions killed while defending the planet. His death was reported shortly after the Battle of New Alexandria[3] in 2552 by members of Sigma-Alpha.

The three remaining members of Sigma-Alpha would take the survivors from Upsilon and Tau teams into their group following their narrow escape from Reach aboard the UNSC Bright New Day. In the following weeks Sigma would take part in the Loss of Hope near the end of the battle, and the Battle of the Zenith Complex immediately after. It was here that they would encounter SPARTAN-071 for the first time in decades during a mission to secure Forerunner data for the Office of Naval Intelligence. Shortly afterwards, Sigma would participate in the unsanctioned Operation: MOBY DICK, surviving the costly operation before fleeing back towards the Sol System. Sigma-Alpha would not make it back to Earth until the Covenant already began their invasion, sacrificing their ship to destroy a Covenant cruiser and taking part in the Battle for Moscow alongside Whiskey-04. The Spartans would be part of a number of smaller operations towards the end of the war, though they would remain on Earth during the decisive Battle of the Ark. Following the end of the Human-Covenant War, Sigma-Alpha would take part in a number of smaller operations, largely against Covenant remnants and Insurrectionists. The Sigma Project was shut down in January of 2554 due to the Spartan branch's increasing prevalence, though some members remained within the UNSC Navy.


Sigma-Alpha's survivors in 2558: Jax-007, Kane-098 and Marco-035.

Despite its status as a little-known, secretive project that was completely overshadowed by other SPARTAN programs, Project SIGMA's Spartans accomplished a great deal during their active years and were responsible for multiple victories over the Covenant Empire. Records of SIGMA would be kept secret from the general public and any surviving support staff were either paid off or kept under heavy surveillance to prevent word of the project's existence from leaking out. By 2558 at least five SPARTAN-II's from the program were considered active and fit for military service, though they would largely be consigned to separate stations due to being so highly sought-after by various groups within the military for their tactical expertise and skillsets.


This list is accurate as of January 1st, 2558, four years after the official end of Project SIGMA. [4].

Second-Generation SIGMA

"I am Doctor Calvin Roe of the Office of Naval Intelligence. You are all now part of the second generation of Project SIGMA. The twelve of you will comprise UPSILON and TAU teams, as part of a new Spartan initiative. Your work for humanity has only just begun."
―Roe, speaking to the survivors of Operation: PROMETHEUS

In early 2537, long after the original SIGMA Spartans had been sent off to war, the plan was made for the recruitment of groups of SPARTAN-III soldiers to serve as a new generation of soldiers under the direct command of ONI, rather than serving on suicide missions like their brethren. While some members of the 300-strong Alpha Company were pulled for this very purpose, at the behest of Lieutenant Kurt Ambrose, their trainer, to operate elsewhere, the decision was made that more would be needed to carry out operations that even their SPARTAN peers would be unaware of. Operation: PROMETHEUS, which took place in late 2537, proved to be the most dangerous mission undertaken by Alpha Company, and culminated in the deaths of all but twelve participants, who were able, albeit barely, to escape K7-49, the mission location, and return safely to a nearby Prowler. Once aboard, they were met by Margaret Parangosky, Calvin Roe, and Colonel James Ackerson, the progenitor of SPARTAN-III. There, the decision was made to keep their survival a secret, and incorporate these survivors into two teams, aptly named UPSILON and TAU, making up a second generation of SIGMA Spartans under Roe's instruction.

Due to the relatively small size of the SPARTAN-III group, and the augmentation procedures they had undergone, known as Project: CHRYSANTHEMUM, it was decided that both teams would be eligible for MJOLNIR armour usage. Despite the astronomical cost of a dozen suits, this was justified as it would greatly improve their performance on the battlefield, where they were sorely needed. This was approved, the twelve members of Upsilon and Tau gradually being trained to use their MJOLNIR suits. Unlike the members of Noble Team, who possessed similar 'superior' genes to the SPARTAN-II candidates, these Spartans were originally made to wear cut-down MJOLNIR suits in combat, their augmented bodies gradually adjusting as time went on. Like the original SIGMA units, Upsilon and Tau were sent on smaller strike operations against the Covenant, fielded as shock troops on the frontlines in various campaigns over the years, proving to be quite effective as groups. The two teams were often used in conjunction with one another, Upsilon specialising in heavy firepower and demolition operations, while Tau became proficient in missions that required subtlety and stealth. As the SPARTAN-II's were constantly being deployed in the field under the command of the UNSC Navy for the most part, they remained unaware of the SPARTAN-III's existence for some time.


The only SPARTAN-III SIGMA members to survive the Fall of Reach: Martin-A136, Louie-A199 and Alex-A121.

These Spartans operated efficiently for many years, eventually coming into contact with Sigma-Alpha Team during the Siege of Fargad. The mass SPARTAN presence during the battle was a major boon for the UNSC defenders, who in spite of retreating had inflicted massive casualties on the enemy fleet and slowed down the Covenant advance into the Inner Colonies. They would continue to operate for years after this, augmenting Marine and Army units on ground campaigns and building up a formidable reputation as excellent if savage fighters. With the Fall of Reach in late 2552, nine out of the twelve SPARTAN-III Sigma members were killed over the course of a month, making Reach the biggest loss of SPARTAN life since TORPEDO and PROMETHEUS. Their deaths came as a surprise hen reported to HIGHCOM, considering the excellent survival record these Spartans had possessed beforehand. As per the Cole Protocol, their bodies were disposed of or made inaccessible to the Covenant by their surviving comrades. The three survivors were folded into the remnants of Sigma-Alpha for the remainder of the Human-Covenant War.


This list is accurate as of January 1st, 2558, four years after the official end of Project SIGMA.

Project Shutdown

With both Richard Mack Senior and Calvin Roe killed in 2552, Project SIGMA was left with no real leadership. Those few who were aware of the project and alive at the time had been reassigned to other projects by this point by ONI and most of the SPARTAN personnel were either dead or missing. As such, the surviving Spartans were transferred into the joint unit under ONI's supervision in 2553. Project SIGMA continued to officially operate for another year as the accumulated data was compiled and personnel accounted for. It was shut down for good in 2554, having been completely superseded by Spartan Operations, which dealt with all remaining SPARTAN-II and SPARTAN-III soldiers and was the main body in charge of their deployments. Several SPARTAN-II members of the project did remain with the UNSC Navy instead of joining the branch due to their long-standing affiliation with the branch.

Behind the Scenes/Trivia

  • The idea for a 'Project Sigma' was made shortly after this user started work on this wiki, with the belief that it could help to explain the discrepancy in SPARTAN-II and III numbers during the war. Over time this was greatly revised and expanded to become what it is today.
  • Due to new SPARTAN-II tags emerging as new Halo content is created, any SIGMA candidates with conflicting tags can be assumed as part of a group discovered after Catherine Halsey's initial sweep that were given numbers originally belonging to the Reach-trained Spartans.


  1. Later tests proved that he had in fact received a fatal gunshot to the head from Jack, a fight having evidently broken out between the pair
  2. Post-War data suggests that Sigma-Gamma discovered a Forerunner device, most likely a highly advanced Slipspace translocator that transported them to an unknown location.
  3. While Sigma-Alpha reported his demise, eyewitness accounts and partially-deleted helmet recorders heavily suggest that SPARTAN-035 killed Roe, though there was no conclusive evidence.
  4. This list does not regard ONI Directive 930
  5. Sigma-Gamma were declared MIA in 2548 following an operation in the Outer Colonies, upon destroying an entire Covenant Legion as they tried to take control of an unknown alien artefact. The SPARTAN Team continued to make transmissions for several hours following the destruction of the site, despite not being found, leading to the MIA status.
  6. Though not conclusive, there is some evidence to suggest his involvement with the Insurrection, possibly commanding their forces at Endrin until Operation: SWEEPOUT in 2550.
  7. Assigned to Project THOR along with other SPARTAN assets deemed 'unstable' following psychiatric evaluation in 2554
  8. It is largely unknown as to why the records of this particular S-II are either deleted or untraceable, though dedicated searches come up with the following code: CDRΣS142UNK/MIA. His whereabouts after his augmentations are unknown outside the highest echelons of the UNSC.
  9. Awarded the Colonial Cross posthumously.
  10. Post-War analysis of the incident suggests that this was a friendly fire event perpetrated by Codename: PYRRHUS, who was killed not long after.
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