Project: CHRYSANTHEMUM was the codename given to the SPARTAN-III biological augmentation procedures. They represented a significant improvement over the augmentations used in the previous SPARTAN-II Program, being safer and far less invasive to perform while producing similar results.
The CHRYSANTHEMUM bioaugmentation set improved upon the augmentations of the SPARTAN-II program, pioneered by Dr. Catherine Halsey. With advances in technology, the casualty rate for SPARTAN-III candidates was usually 0%, as opposed to the 56% casualty rate of the SPARTAN-IIs. The genetic requirements for the candidates could also be loosened from the exceedingly strict criteria of the previous program, although the range of compatible individuals still remained incredibly narrow, with any aberrations from the required genetic set increasing the risk of failure to an unacceptable level. The broader selection criteria also made potential behavioral problems more likely among the SPARTAN-IIIs.
The Spartan-IIIs' augmentations were chemically induced instead of surgically implanted like many of the SPARTAN-II enhancements, and they had no need of a growth hormone catalyst in the form of a thyroid implant like the SPARTAN-IIs. However, the augmentations also still had to be administered at the onset of puberty like in the previous program, as the bodies of either prepubescents or adults would reject the chemicals. Due to the Office of Naval Intelligence accelerating the schedule of the program in order to have the Spartans deployed in the field within a shorter span of time, puberty was artificially induced for the candidates via human growth hormone as well as cartilage, muscle and bone supplements added into their food. As a result, the candidates had the bodies of near-adult Olympic athletes at an average of only twelve years of age, and it took some time for them to acclimatize to their larger physiques.
 All SPARTAN-IIIs
|8942-LQ99||"carbide ceramic ossification catalyst" drug.||Skeletons become virtually unbreakable, allowing survival in harder impacts.|
|88005-MX77||"fibroid muscular protein complex" drug.||Increased density of individual's muscles, greatly enhancing physical strength.|
|88947-OP24||"retina-inversion stabilizer" drug.||Color sharpness is significantly improved upon, and night vision is heightened.|
|87556-UD61||improve the colloidal neural disunification solution||Greatly improves the individual's reaction time, decreasing the time taken to react by 300%; "Spartan time".|
 Gamma Company
In addition to the standard set of chemicals, Kurt Ambrose covertly had a set of three additional drugs added to the augmentations of Gamma Company in hopes of increasing their survivability in the field. All of the three had been outlawed by the UNSC Medical Corps in 2513.
|009762-OO||Neural-altering non-carcinogenic mutagen.||Alters key regions in the individual's frontal lobe. Enhances aggressive response to dangerous levels. Requires regular doses of 009127-PX and 009927-DG to be taken to avoid uncontrollable aggression.|
|009127-PX||cyclodexione-4, bipolar integration drug||Counters the effects of 009762-OO.|
|009927-DG||miso-olanzapine||Counters the psychological effects of 009762-OO.|
The CHRYSANTHEMUM procedures took place aboard the mobile hospital ship UNSC Hopeful. The augmentations were administered over the course of a week; the subject was kept in a mostly sedated state throughout the process, which was conducted in a large, open operations room housing 400 sections separated by semi-opaque plastic curtains. Each compartment was filled with medical equipment, including a sterile field generator overhead as well as vital signs monitors and a chemotherapeutic infuser. The infuser contained vials for the various chemicals, which were administered to the subject via IV and osmotic patches. The Spartans were given a number of drugs to allow them to withstand the procedures themselves and counter their potential negative effects; these included shock reducers, analgesics, anti-inflammatories, anticoagulants, and pH buffers.
Despite the SPARTAN-IIIs' expendable nature and lower-grade equipment than the SPARTAN-IIs, their enhancements represented a "quantum leap" over the previous program's bioaugmentation set. As a result, the SPARTAN-IIIs are virtually equal to the SPARTAN-IIs in terms of physical capabilities and similarly capable of superhuman feats associated with Spartans. While most SPARTAN-IIIs were issued with SPI armor as opposed to MJOLNIR for budgetary reasons, the small number that did receive SPARTAN-II grade equipment were in many ways indistinguishable from SPARTAN-IIs.
During Operation: TORPEDO, Tom-B292, 12 years old at the time and equipped only with SPI armor, engaged a Sangheili armed with a plasma pistol and an energy sword in hand-to-hand combat. The Spartan's enhanced reflexes allowed him to dodge a plasma pistol bolt and sword swing at point blank range. He then proceeded to throw the Elite to the ground and finish it off with his assault rifle. During the battle, Elites and Jackals moved out of cover because they realized that it was suicide to face Spartans in close quarters.
The muscular augmentations provided an individual SPARTAN-III the strength of "three normal soldiers". During Operation: TORPEDO, SPARTAN-IIIs ran at a speed of nearly 30 KPH (around 18 MPH). Spartan-IIIs were also described to have been moving with "speed and reflexes that no Covenant could follow". "They dodged, snapped necks and limbs, and with captured energy swords, they cut through the enemy until the field ran with rivers of gore and blue blood". Approximately 300 Spartan-IIIs faced thousands upon thousands of Covenant, including Covenant air support, and were described to have been winning the battle until 7 Covenant cruisers emerged as reinforcements.
It was stated by CPO Mendez that Spartans only grew stronger and faster as their bodies grew accustomed to their augmentations. During the battle on Pegasi Delta, most of Beta Company were roughly twelve years old. If the Spartan-IIIs lived long enough to mature, their physical abilities would have improved significantly.
The mutagen 009762-OO, administered only to the Spartans of Gamma Company, makes the Spartans almost completely immune to shock under extreme stress, allowing them to endure injuries and physical pain beyond even a SPARTAN-II; for example, Dante-G188 remained standing momentarily after a number of Needler rounds had blown his chest open, initially not even realizing his grave injuries. As a side effect, the drug suppresses higher brain functions over time; without the regularly administered counteragents, cyclodexione-4 and miso-olanzapine, the Spartan would lose their strategic judgment and become more prone to impulsive, instinct-driven behavior.
 List of appearances
- Halo: Ghosts of Onyx (First appearance)
- Remember Reach
- Halo: Glasslands (Mentioned only)
- ^ a b c d e Halo: Ghost of Onyx, page 63
- ^ a b c d e f g h i j Halo: Ghosts of Onyx, pages 101-102
- ^ Halo: Ghosts of Onyx, pages 82-83
- ^ Halo: Ghosts of Onyx, pages 98, 100
- ^ a b c d e Halo: Ghost of Onyx, page 107
- ^ Halo: Reach
- ^ a b c Halo: Ghosts of Onyx, pages 21-23
- ^ Halo: Ghosts of Onyx, page 99
- ^ Halo: Ghosts of Onyx, page 17
- ^ Halo: The Fall of Reach, page 73
- ^ Halo: Ghosts of Onyx, page 340