Project SIGMA

"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. Since I am aware of the controversy surrounding the of SPARTAN-II's own methodology and attitude, 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 keeping the same asset that benefit the other candidates for the much-needed program"

- Calvin Roe, ONI Civilian Consultant 394382, speaking in 2517

Origins
Project SIGMA was a 'splinter' group of the little-known and highly controversial, established in 2517 after being approved for activation by HIGHCOM. 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 was intended as an offshoot, 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, much of which was later incorporated into the iconic MJOLNIR armour suits that served the SPARTAN-II soldiers for decades.

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 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. 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 with him previously.

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 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. 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.

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. 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, however, 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. 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. Sigma-Delta would consist of a single member, who would be given to HIGHCOM for their own specific uses, officially ceasing to exist in any way after his augmentations.

SPARTAN-II SIGMA trainees
This list is accurate as of March 3rd, 2553, and the official end of the Human-Covenant War.