The SPARTAN-IV program uses only consenting adult volunteers, the augmentation of adults having been made possible by advancements in the technologies pioneered by the prior Spartan programs. Unlike the mainline SPARTAN-IIIs who were forced to use SPI Armor due to budgetary constraints, all Spartan-IVs are equipped with MJOLNIR armor, now mass-produced by several private companies. The Spartan-IVs serve in a dedicated UNSC service branch known as Spartan Operations, whereas their forebears operated within other chains of command. Unlike the other military branches, the Spartans lack a formal rank hierarchy altogether, instead employing a more malleable framework based on an individual Spartan's skills and specialization.
Like the augmentations performed for the Spartan-IIs and the improved procedures utilized in the subsequent SPARTAN-III program, the Spartan-IVs undergo a series of procedures to enhance their physical capabilities and to wear Mjolnir powered armor. 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. By the time of the initiation of the SPARTAN-IV program, the technology had advanced to the point that adults could be augmented without major risk, although the improvements to the subject's strength and speed are not as extensive as in the previous two programs. As such, the newest generation of MJOLNIR armor increases the speed, strength, endurance and reaction time of the Spartan's without putting as much stress on the body which would require more extensive augmentations similar to that of the Spartan-II program. This means that The pool of candidates for the Spartan-IV program could be expanded much further than the previous Spartan programs.