List of changes in Halo: The Fall of Reach rereleases

Halo: The Fall of Reach was first published in 2001, and since then has been adapted multiple times in different formats. Changes to the novels include grammatical fixes, resolved inconsistencies, and new bonus content. Changes in graphic media include modified, omitted, or added dialog and scenes; amalgamated character roles; and visual depictions varying from their original descriptions.

2010 Tor Books rerelease

 * The rerelease includes an Adjunct section at the end with several new pieces of short fiction:
 * ONI Directorate Memorandum Interrogation Findings - a series of excerpts from the interrogation of Subject 386 by Admiral Cole after the Battle of the Great Bear in 2530.
 * Word from the Third Fleet of Glorious Consequence - a message sent by Supreme Commander Luro 'Taralumee to the Vice Cleric of Zeal, after the Battle of Miridem.
 * A transmission from Vice Admiral Berlin M. Tursk to Captain Lucius Jiron, concerning the capture of Dr. Catherine Halsey during the Battle of Miridem and the UNSC response.
 * A message from Mike to Agnes, regarding Ralph-103's upbringing and reintegration into society following his dismissal from the SPARTAN-II program.
 * United Nations Space Command Transmission 34670J-17 - A transmission sent by Captain Jacob Keyes of to Vice Admiral Kopano N'Singile of Reach Central Command in 2552.
 * An ONI post-incident investigation report on a possible security breach that may have contributed to the Covenant's discovery of Reach. It involves a transcript of a SecNet conversation between Sergeants Joseph M. Poteet and Alasdair R. Schicker.
 * WINTER CONTINGENCY Declaration Supplemental Orders, an ONI directive containing orders for field agents on Reach in the event of a WINTER CONTINGENCY declaration.


 * The dropship used to transport the 75 Spartan-II trainees to the Military Wilderness Training Preserve in Chapter 5 was originally identified as a Pelican, whose troop bay would be far too small for 75 people. In the reissue the dropship is changed into a larger Albatross.


 * On page 46 of the original edition, Kelly-087 hands out parts of a map to the 75 Spartan trainees. Then on page 48, when John checks to make sure the children arrived at the lake, he counted only 67. In the re-release, the count of 67 is changed to 74.


 * In the original edition, when the Spartans are browsing through the cargo manifest of the freighter Laden, the ship is said to carry champagne of a "Beta Centauri vintage", implying the Beta Centauri system had been colonized by humanity. In the re-release, "Beta Centauri" has been changed to "Procyon". This is likely due to the fact the system is situated well beyond the known sphere of influence of humanity and thus unlikely to house a colony.


 * In the original edition, Captain Keyes refers to Ensign William Lovell as "Michael" when first meeting him. This has been corrected in the 2010 edition.


 * In the original, a UNSC frigate was referred to as the Alliance, and then shortly thereafter as the Allegiance. In the 2010 edition, the ship is referred to as the Allegiance in both instances.


 * In the original edition, the ship was referred to as a cruiser and then later as a carrier. In the 2010 edition, the ship is referred to as a cruiser in both instances.


 * On page 19, Michael Stanforth was said to be a Vice Admiral, and on page 95, it said he was a Rear Admiral. In the 2010 edition, he is referred to as a Vice Admiral in both instances.


 * In the original edition, Vice Admiral Stanforth was stated to be ten years Dr. Halsey's senior. "Ten years" is changed to "six years" in the 2010 edition, most likely to accommodate Stanforth's and Halsey's birth dates established in the ONI memorial in Halo 3: ODST.


 * In the 2001 edition, the Pillar of Autumn is said to be missing its port-side emergency thrusters, though it later uses them twice. In the 2010 edition, the mention of the thrusters being missing has been removed.


 * In Chapter 22, James-005's left arm is burnt off by an assault cannon. In the original edition, it is said a few pages later that he saluted with his left hand—while it was still missing. In the 2010 re-release, he salutes with his right hand.


 * In the original edition, the first time John-117 encounters Sangheili warriors in the battlefield is on Gamma Station during the Fall of Reach. In addition, the UNSC is depicted as not having any first-hand intelligence on the species prior to the battle; Dr. Halsey only speculates their existence. This was ignored in later material; in the subsequent Eric Nylund novel Halo: First Strike, the Spartans of Red Team casually refer to the Elites at a time they would have been no more familiar with them than John and Blue Team aboard Gamma Station, and in Halo: Ghosts of Onyx, the Spartan-IIIs encounter Sangheili as early as 2537 and 2545. Later fiction has portrayed Sangheili as having been present in battles throughout the war numerous times. References to the Sangheili as being a never-before-seen species were altered to be more in line with the revised canon in the reissue. When Dr. Halsey briefs the Spartans for Operation: RED FLAG in chapter 26, the line
 * "We believe there is a 'race' of field commanders, which we are currently calling 'Elites'"
 * is changed into:
 * "We also know that there is a 'race' of field commanders we have historically called 'Elites'".
 * During the Spartans' mission to Reach Station Gamma in chapter 35, the following sentence:
 * "These must be the elite warrior class Dr. Halsey had conjectured. The Covenant's best? They were about to find out."
 * is changed into:
 * "These were Elites - the iron heart of the Covenant. Would they best the Spartans this time? They were about to find out."


 * In chapter 29, the sentence
 * "From this distance, the Pillar of Autumn could have been mistaken for an elongated frigate."
 * is changed into:
 * "From this distance, the Pillar of Autumn could have been mistaken for a Marathon-class carrier."
 * It should be noted that this is also an error, as Marathon is actually a class of cruiser.


 * The number of the Covenant ships present at the battle over Reach is changed from 314 to "well over seven hundred" in the 2010 reissue. This may be due to a line spoken by Fleet Admiral Terrence Hood in Halo 2, where he states that the fleet that destroyed Reach was "fifty times" the size of the Fleet of Sacred Consecration. However the change is only made once while all other instances state the fleet consists of 314 ships.


 * During Blue Team's mission to Reach Station Gamma, the original edition states that Kelly shouted "All secure!" while the Spartans' Pelican prepares for maneuvering, even though she is not aboard the Pelican. "Kelly" has been corrected to "Linda" in the reissue.


 * In the 2001 edition, Admiral Roland Freemont recalls all UNSC warships in the "REACH, JERICO [sic] and TANTALUS systems" to the defense of Reach. The 2010 reissue changes the spelling of "JERICO" to "JERICHO", but the rest of the line remains unchanged.

2011 Definitive Edition rerelease

 * The number of ships at Reach is changed back from 700 to the original 314.


 * The reference to the Tantalus and Jericho systems has been removed. This is because Tantalus is another planet in the Epsilon Eridani system and the "Jericho system" had been invaded by the Covenant in 2535.

General changes

 * There are several changes regarding various characters' hairstyles.
 * Kelly-087 is depicted with brown hair in the Spartans' first day of training, whereas in the novel, she had her hair dyed blue at the time. She is also depicted with a bob-cut hairstyle in later scenes of childhood training; according to Dr. Halsey's personal journal, Kelly, like the other Spartans, had her head shaved a few days after her induction into the program, with an entry describing how she had to be held down for the barbers to finish cutting her hair. Kelly is also depicted with medium-length hair in the scenes following the augmentation procedures; in the book, her hair had yet to grow back after the augmentations at the time of the Spartans' mission to Eridanus Secundus, and even later in her career she is described with a short military cut.
 * Linda-058 maintains a rather long haircut in the comic, while the novel describes her as having close-cropped hair.
 * The comic consistently portrays Dr. Halsey with black hair; the novel mentions that her hair had started graying by 2525 being completely gray by 2552.
 * There are a number of differences involving the attire of characters.
 * The comic does not depict Dr. Halsey with glasses at any point, whereas the book describes her as wearing glasses in most of her appearances.
 * During the Spartan-II trainees' mission in the Military Wilderness Training Preserve, the Spartans are shown wearing their standard training fatigues. In the novel, they wear heavy parkas because of the cold.
 * In Admiral Stanforth's initial briefing on the Covenant and the destruction of Harvest in Boot Camp, Stanforth wears a green uniform vaguely similar to the standard Navy service uniform. Mendez and Halsey are wearing similar outfits, teal and light gray in coloration, respectively. The novel describes Stanforth and Mendez as wearing black dress uniforms, with Mendez's chest covered with decorations while Stanforth's uniform is undecorated; Halsey is described as wearing gray slacks and a black shirt with her glasses hanging about her neck on a gold chain.
 * Like Halo Wars: Genesis, the series depicts space battles with considerable artistic license. In the novel, space engagements are consistently described as occurring over distances of many thousands of kilometers. For example, when the Unrelenting performs a slipspace jump near the Commonwealth, a distance of three thousand kilometers is considered to be dangerously close, enough to trigger collision alarms. Meanwhile, in the comic, ships and entire fleets exchange fire within visible range, often merely hundreds of meters from one another. This is simply a pragmatic storytelling approach and does not reflect the actual nature of space battles in the Halo universe.
 * Slipspace is depicted as a bright, blue-white tunnel with streams of lines and quadrilateral figures; in the novels, slipspace is described as being pitch black.

Boot Camp

 * Issue 1 features a new prologue centered on Colonel Watts' actions during Operation: TREBUCHET, replacing the novel's prologue featuring Blue Team battling an Unggoy horde on Jericho VII.
 * The events of the first chapter are depicted with a number of differences. In the comic, Dr. Halsey is already awake and on the Han ' s bridge by the time Jacob Keyes wakes up from cryo. In the book, Halsey awakens immediately after Keyes. Keyes is also shown wearing clothes upon waking, whereas in the novel, both Keyes and Halsey are naked while in cryo; similar concessions are applied to all scenes involving cryosleep in visual Halo media. Han ' s trip to Eridanus II is also truncated, and the shuttle's gravitational slingshot maneuver around a local gas giant is omitted.
 * Eridanus II is depicted with two moons. In the Bestiarum, the planet is established to have a single natural satellite, Ehilend.
 * In Issue 1, Vice Admiral Ysionris Jeromi sends Halsey his results on the SPARTAN-II augmentation procedures just after the children are kidnapped in 2517. In the book, he sends the results in 2525, just before the surgeries begin.
 * A new scene is included depicting the UNSC Dartmouth under a pirate attack by Watts' ship.
 * A new scene is added in which John dreams of Dr. Halsey waking him up in his first day of training.
 * The scenes depicting the Spartans' first days of training are compressed into a montage and the two consecutive "Ring the Bell" exercises are omitted as the impetus for John befriending Sam and Kelly.
 * In the novel, CPO Mendez gives John no answer when the Spartan asks if the dead candidates' lives were wasted or spent. In the comic, he avoids the question by telling John to get some rest.
 * When CPO Mendez and Dr. Halsey enter the titanium mine where the newly-augmented Spartans are training, Mendez's Warthog lacks a turret. In the novel, the Warthog is mentioned as being equipped with a missile launcher.
 * The incident aboard the UNSC Atlas with the four ODSTs in the gym is omitted.
 * It is said that Colonel Watts defected from the UNSC in 2512; this addition is repeated in the animated series. This contradicts the background first given for the character in the Halo Encyclopedia and later Watts' Halo Waypoint article, with the former establishing that Watts already led the Eridanus rebels in 2494 and the latter stating that the colonel went turncoat as early as the 2480s.
 * John is shown having a nightmare while sleeping aboard the Laden; in the novel he merely dreams of gravball and a coin spinning in the air.
 * In Issue 3, John pushes Sam out of the line of fire and is wounded during the assault on Eridanus Secundus. In the novel, John is merely grazed by a lucky shot.
 * The specifics of the Spartans' capture of Colonel Watts differs from the novel. In the comic book, Watts is shown entering a safe room before the Spartans capture him, which does not occur in the novel. The crate Watts is forced into is thrown off his apartment's balcony in the comic, whereas in the novel, the Spartans slide it down by a rope.
 * The first transmission from the Covenant to humanity that tells them their destruction is the will of the gods is an audio message in the novel. In the comic it is a video, with the Prophet of Regret personally appearing to announce it to them.
 * In the same scene, the Covenant ship first encountered at Harvest is depicted as a CCS-class or CRS-class cruiser, presumably Rapid Conversion. Halo Wars: Genesis shows and The Impossible Life and the Possible Death of Preston J. Cole explicitly states that the ship encountered by Battle Group 4 was a super-destroyer.
 * John's last meeting with CPO Mendez and the latter giving the former back the quarter that decided his entry into the SPARTAN-II program is omitted in the comic.

Covenant

 * Unrelenting is depicted as a traditional cruiser in the comic, while the book describes it as a sleek ovoid a third the mass of the Commonwealth, with a single lateral line running fore to aft.
 * In the comic, the Damascus Testing Facility is depicted as a space station orbiting Chi Ceti IV; the source novel and Dr. Halsey's journal describe it as a base located deep underground.
 * Longsword Squadron Delta survives the detonation of the Shiva missile fired at the Unrelenting, whereas in the novel the Longswords are consumed by the explosion, as they were intentionally sacrificed as a diversion.
 * The Spartans' assault on Unrelenting is decidedly different.
 * The comic depicts John, Sam, and Kelly jumping toward the ship—shown within clearly visible distance—without apparent thrusters. The three approach the Unrelenting in a tight formation while discussing their entry strategy and simply glide into the ship. In the novel, the distances involved are much greater. Even though the Spartans use thruster packs, there is a high likelihood of missing the ship which is traveling at a high velocity, forcing the Spartans to conduct careful maneuvers to intercept it. In the novel, the Spartans do not approach Unrelenting in a closely packed group and do not converse until regrouping on the Covenant ship's hull.
 * In Covenant, only John, Kelly, and Sam take part in the assault on Unrelenting, as they are the only three able to don their MJOLNIR armor in time. In the novel, all the Spartans take part in the assault, but only John, Kelly, and Sam are able to get aboard the enemy vessel.
 * In the book, Commonwealth fires a salvo of Archer missiles as decoys to cover the Spartans' approach; this is not depicted in the comic. The warheads used by the Spartans during the boarding operation are also different; in the comic, the Spartans use nuclear missiles, perhaps Shivas. In the book, they use ANVIL-II Air-to-Surface Missiles, which have conventional warheads. As seen in this image, the missiles used in the comic are far too large to be ANVIL-IIs.
 * The shot which seals Sam's fate strikes him in the chest. In the novel, he is struck in the side.
 * While escaping the Unrelenting, John and Kelly encounter several Jackals; this is not described in the book.
 * In the novel, there are four surviving Marines in Corporal Harland's fireteam at the Battle of Sigma Octanus IV. Private Walker freezes, forcing Private Cochran to shoot down two pursuing Banshees with Walker's rocket launcher. In the comic, Cochran is not present. Instead, Walker is able to break out of his fugue and shoot down the lone Banshee pursuing them.
 * The choice to remove Cochran was very likely due to the difficulties of drawing four men in a three-seat Warthog.
 * The initial skirmish above Sigma Octanus IV, the Keyes Loop, and Keyes' promotion to captain are omitted from the comic.
 * In the novel, Blue Team's fight with the Hunters in the Côte d'Azur Museum of Natural History is won by using shredder rounds to break the floor beneath their feet then pushing a stone monolith into the hole to crush them. In the comic, the battle is won by using two grenades to crack the monolith, then breaking it, so that the upper half falls and crushes the Hunters.

Invasion

 * In the novel, John meets Cortana for the first time when she is plugged into his neural interface, where the two have a short conversation. In the comic, Cortana is introduced to John via hologram.
 * In Issue 4, a Sangheili Zealot impales Linda on an energy sword. In the novel, she is shot five times with plasma projectiles.
 * Invasion adds a subplot with Red Team being deployed on Reach to defend Orbital Defense Generator Facility A-331; this sequence is not present in The Fall of Reach but is instead loosely adapted from Halo: First Strike with significant changes from the original narrative.
 * The Spartans' Pelican is piloted by Fred and Kelly with Joshua manning its troop bay gun; in First Strike, no rear gun is in evidence and the Pelican is piloted by a Naval aviator.
 * The Longswords escorting the Pelican are omitted in the comic.
 * The dropship is pursued—and shot down—by Banshees. In the book, the Covenant craft are Type-31 Seraph fighters instead.
 * The Pelican crashes with the Spartans still on board; in First Strike, the Pelican is traveling much faster, forcing the Spartans to exit at a high altitude before it crashes into a mountainside at a supersonic velocity. The subsequent part of the book detailing the Spartans' regrouping and advance on the generator complex is also omitted in the comic.
 * The events at the generator facility are portrayed with notable differences, including the Spartans encountering a single delirious Marine as opposed to the four moderately shaken survivors of Charlie Company.
 * In the comic, all the Spartans of Red Team remain at ODG A-331 when the Covenant launch their second major assault on the facility; in First Strike, only Team Beta remains at the complex by the time of the Covenant attack.
 * In an added scene, the Master Chief dreams of his and Kelly's young selves reflecting on the possibility of returning home someday while in cryosleep.

Fall of Reach animated adaptation
The animated adaptation, like the comic series before it, features several changes necessitated by its medium. The greatest change is that in order to keep the length of the series to approximately one hour this adaptation only covers the first half of the story ("Reveille" and "Boot" in the novel; "Bootcamp" and the first two issues of "Covenant" in the comics). This is also due to the fact that the animated series was released alongside Halo 5: Guardians and serves to educate viewers of the history of Blue Team, whereas the novel and comic adaptation serve as prequels to Halo: Combat Evolved. Listed below are the changes which are present in the animated series; due to their overwhelming number, simple omissions or truncations are not listed. Changes which are in keeping with one previous adaptation but not the other are listed as such.
 * The series opens and closes with all-new scenes in which Blue Team meets on a glassed Reach and reminisces about their past prior to the events of Halo 5: Guardians.
 * Rather than the third-person perspectives of the source material, the three parts of the series are narrated from the perspectives of Catherine Halsey, Sam-034 and Kelly-087, respectively.
 * The characters' attire and physical characteristics generally conform to their comic representations rather than their descriptions in the novel. Notably:
 * Halsey's civilian attire while observing John is nearly the same as depicted in the comic (though Keyes' suit is noticeably more casual than in either previous adaptation).
 * Halsey is depicted without glasses.
 * Kelly is abducted with her hair its natural brown rather than dyed blue. She is also depicted as having brown eyes, whereas the novels as well as prior depictions portray her with blue eyes. Fred-104 is similarly depicted with brown eyes; he is described as having blue-green eyes in the novels.
 * In the novel, Samuel-034 is described as having darkly tanned skin and green eyes. After the Spartans' augmentations he is noted as having grown his hair out to three centimeters. In the animated series, he has a pale complexion, blue eyes, and maintains a short buzz cut until his death.
 * Unlike the comic adaptation, in which the 14-year-old John-117's face is always partially obscured whenever he appears without a helmet, his face is fully shown in the animated series.
 * Keyes' revival on the Han in shown in the manner of the comic, rather than the novel.
 * John and the other boys play King of the Hill on series of platforms, rather than a literal hill.
 * Halsey tosses the quarter in the air multiple times (with John correctly estimating which side it will land on each time), whereas in the novel she flips it only once.
 * When Halsey first addresses the Spartan cadets, they have all had their hair shaved into buzz cuts. In both previous adaptations, they all had their civilian haircuts at this time, with their hair not being shorn until several days into the program, as attested by Dr. Halsey's personal journal.
 * Jorge-052 makes a brief cameo in which he is hit with a humbler stun device for correcting a drill instructor on the pronunciation of his name.
 * Three Spartan-II candidates die early in the training. Halsey's narration refers to this as "removing the chaff from the wheat". All previous canon sources explicitly state that all seventy-five trainees survived until the augmentations. Nevertheless, following the SPARTAN-II augmentation procedures Halsey explicitly states that twenty-seven children died, representing thirty-six percent of the candidates, math which only holds true if all seventy-five underwent the procedures.
 * The "ring the bell" exercise is once again included, though with several differences: the events take place some time into the training, rather than on the first day; the obstacle course is indoors, rather than outdoors; and John's team includes all of Blue Team, Fred and Linda included, rather than just himself, Sam and Kelly. Only the first bell exercise is shown.
 * The mission in the Military Wilderness Training Preserve takes place in below-freezing conditions, as described in the novel, rather than the temperate environment of the comic. The trainees wear thin (though presumably insulated) body suits, rather than the novel's heavy parkas.
 * During John's debriefing after the wilderness mission, a brief scene is added in which Halsey tells John that the 300 Spartans at Thermopylae were betrayed, though their sacrifice saved Greece; this serves as foreshadowing of the events of Hunt the Truth and Halo 5: Guardians. John also asks about the highest rank he can attain, and is told that the highest nom-commissioned rank is Master Chief Petty Officer. John vows to achieve this rank, foreshadowing his future nickname.
 * As in the novel, Vice Admiral Ysionris Jeromi's report is received immediately before the augmentation procedures in 2525, though it is an audio message rather than the text file of the novel or the video message of the comic.
 * As in the comic, CPO Mendez tells John to get some rest when asked whether the Spartans' lives were spent or wasted. A new scene is added in which immediately following this conversation, Sam attempts to comfort John and invites him to the shooting range. John declines the offer and heads to the gym, setting up his confrontation with the ODSTs, events which take place more than three weeks later in the novel.
 * Sam's narration states that John was still struggling with the loss of his men when he fought the ODSTs, implying that he was not in control of his emotions. John is also shown climbing on top of and repeatedly pummeling a fallen ODST (punching him at least 15 times), fighting far more aggressively and offensively than is depicted in the novel, in which he only strikes at the ODSTs when attacked. The fight takes place entirely on the floor of the gym, rather than in the boxing ring on the orders of a Marine sergeant as in the novel.
 * An added scene shows Halsey watching the fight on a monitor as it takes place, observing John's actions and physical responses with curiosity whilst completely unfazed by the brutality he is inflicting.
 * As in the comic, John has a nightmare while sleeping aboard the Laden.
 * Blue Team uses M7S silenced submachine guns during the assault on Eridanus Secundus rather than MA2B assault rifles, while the Insurrectionists appear to be using standard un-silenced M7 SMG's instead of HMG-38's. Linda also uses an M7S instead of her custom-tuned SRS99C-S2 AM sniper rifle.
 * As in the comic, John is wounded by one of Colonel Watts' guards while pushing Sam out of the line of fire rather than by a random, unlucky shot.
 * In an added conversation, Sam scolds John for sacrificing himself for him, stating, "A queen doesn't sacrifice everything to collect a pawn." To this John replies, "All the pieces go back in the same box when the game is done," in a reference to Cortana's first words.
 * A shortened version John's reunion with Jacob Keyes takes place just before the Spartans are told of the events at Harvest, rather than years later prior to his debrief at Camp Hathcock following the events of the Battle of Sigma Octanus IV (which is not depicted in the series).
 * The Harvest briefing takes place immediately following the Eridanus Secundus raid rather than nearly two months later. The Spartans are wearing black body suits rather than UNSC Navy Dress Uniforms.
 * As in the comics, the first transmission from the Covenant to humanity that tells them their destruction is the will of the gods is a video, however this time the Prophet of Regret remains shrouded in darkness, his features hidden with only his silhouette discernible.
 * As in the comic, the Unrelenting is depicted as a.
 * As in the novel, all of Longsword Squadron Delta is intentionally sacrificed and vaporized by the nuclear explosion.
 * As in the novel, Damascus Testing Facility is an underground facility on the surface of Chi Ceti IV.
 * When first outfitted with the MJOLNIR Mark IV, each of the members of Blue Team is outfitted with same helmet variants they wear in Halo 5: Guardians, save for John who wears the standard Mark IV helmet, and Sam who wears a CQB helmet. In all previous adaptations they all wear identical standard Mark IV armor.
 * The Spartans' assault on the Unrelenting is generally consistent with the comics rather than the novel, though all five members of Blue Team now participate; Fred and Linda enter the ship from the other side then rendezvous with the others at the core and leave the ship together. The Spartans are shown using thrusters built into their MJOLNIR armor - a feature of the MJOLNIR [GEN 2] in Halo 5: Guardians. They also carry the same weapons as they use in Halo 5: Guardians; noticeably, Sam carries a BR85HB battle rifle from Halo 4, which was not yet in service in 2525.
 * Unlike previous adaptations, where the Spartans exclusively encounter thin-headed Ruuhtian Kig-Yar aboard Unrelenting, Blue Team first run into and kill an Unggoy. They then encounter a Sangheili in a hangar bay, where they charge at each other and Sam is shot in the chest; previous adaptations have Sam shot as a door opens in a narrow corridor. Finally, in the core they engage numerous Ibie'shan Kig-Yar, the stout-headed subspecies introduced in Halo 4.
 * In Kelly's added narration she states that, "We knew we weren't finishing the fight, we were just getting started," in reference to John's final words in Halo 2 and Halo: Combat Evolved, respectively.
 * While in the novel the Spartans use the warheads from regular Anvil-II missiles to destroy the Unrelenting, in the animated series the Commonwealth's Pelicans carry HAVOK tactical nuclear weapons which the Spartans use to destroy the ship by attaching one to the Unrelenting's reactor and detonating it. However, like in the novel, they do use a countdown timer attached to the warhead to set it off.