John-117

"They let me pick. Did I ever tell you that? Choose whichever Spartan I wanted. You know me. I did my research. Watched as you became the soldier we needed you to be. Like the others, you were strong and swift and brave. A natural leader. But you had something they didn't. Something no one saw, but me. Can you guess...? Luck."

- Cortana

Master Chief Petty Officer John-117, better known to the public as the Master Chief, is a SPARTAN-II commando of the UNSC Navy's Special Weapons division. He served as one of the most important figures of the Human-Covenant War. After nearly thirty years of active duty, he is one of the most decorated war veterans of the United Nations Space Command, having fought in more than two hundred ground engagements against the Covenant and Insurrection, earning every major service medal except the Prisoner of War Medallion.

For much of his career, John served as the leader of SPARTAN-II Blue Team. As the war neared its end, most of John's fellow SPARTAN-IIs were killed in action during the Fall of Reach. However, John and his AI companion Cortana fled Reach and their vessel fortuitously arrived at Halo Installation 04, a one hundred millennia-old superweapon created by the Forerunners to destroy their parasitic enemy, the Flood, by killing all life in the galaxy. Having destroyed Halo, the surrounding Covenant fleet, and the Flood forces on the ring, John-117 returned to Earth and resisted the Covenant's impromptu invasion. Pursuing the invaders' flagship, the Master Chief encountered Installation 05, where civil war soon broke out within the Covenant. Weeks later, John followed the remaining Covenant forces to the Ark, the Halo Array's control center, which he disabled before the Halos could be fired.

John went missing in action after the war's final battle in December 2552, having stymied the threat of the Covenant, the Flood, and the Halos. In the interbellum, John was lauded as a hero, and though he was officially declared MIA like all Spartans, he was ostensibly believed by the UNSC to have perished. After his recovery in July 2557, he played a key role in the conflict between the UNSC and the Didact's Promethean forces and Covenant devotees, beginning on the shield world Requiem. This culminated in an attack on Earth and the Didact's temporary defeat, as well as the loss of Cortana. John subsequently reunited with Blue Team and with their help, vanquished the Didact for the second time. John and his Spartan compatriots then departed Earth to embark on new missions, eventually falling out of contact with the UNSC.

Among most humans John is known simply by his rank as the "Master Chief" or (erroneously) the "Chief". Within the military he is most commonly identified as "SPARTAN-117" or the phonetic callsign "Sierra 117". As with all Spartans, John was regarded by the Covenant as a "Demon". However, John specifically was known as "the Demon", an epithet he earned after the destruction of Installation 04, while the allied Sangheili referred him as "Spartan".

Early childhood
"Halsey"

- John

Born on March 7, 2511, John lived with his mother and father in Elysium City, on the colony world of Eridanus II. He attended the Elysium City Primary Education Facility Number 119. As a child, John had brown hair, freckles, and a small gap between his front teeth. In a memory, John recalled that his mother was kind and smelled of soap. The would-be UNSC Marine Lieutenant Parisa was a childhood friend of John's. John once saved her from drowning at Lake Gusev, after which John promised to marry her and keep her safe. A photo of the two was also taken by Parisa's father soon after, and would be kept as a memory by Parisa long after she thought John had passed away. He also was a friend of Ellie Bloom, living next to each other in their childhood, and Katrina, who played obstacle race with him and Ellie.

At the age of six, he was identified by Dr. Catherine Halsey as one of 150 preliminary candidates for the SPARTAN-II program. John was an ideal physical and mental candidate, standing a head taller than the majority of his schoolmates, having greater physical proportions, possessing greater strength, exhibiting superior reflexes, and having an aggressive drive for success. By the time he was conscripted, he had a string of forty-five victories in what Dr. Halsey referred to as a "brutal version" of King of the Hill, resulting in him having a chipped tooth and his opponents suffering various bone fractures.



When Dr. Halsey and LTJG Jacob Keyes visited Eridanus II in 2517 to study him, they were impressed with his intellect and luck. In a final test of his viability as a candidate, he was asked to determine which side an old coin would land on. He watched the coin as it flew in the air and caught it before it could land; correctly stating which side was face-up, on the side of the eagle. Later that same year, John and 74 other six-year-old children were conscripted to Reach: they were covertly kidnapped from their homes and replaced with flash clones to cover up the kidnappings. All of the clones would later die of seemingly natural causes as a result of their accelerated growth process, with John's flash-clone dying on December 7, 2517.

Spartan training
"Remember this: you don’t win unless your team wins. One person winning at the expense of the group means that you lose."

- CPO Mendez explaining trainees the main idea of teamwork.

John and the rest of the children chosen for the SPARTAN-II program were brought in the Reach FLEETCOM Military Complex, their new home for the next several years. There, Dr. Halsey informed the children of their new purpose: they were destined to become the protectors of Earth and all its colonies. The next morning John discovered his service tag, stitched into his training uniform, and his new name: John-117. John began adjusting to his new life, training with other Spartans under Chief Petty Officer Franklin Mendez.

In their first training exercise, John was grouped with fellow trainees Kelly-087 and Samuel-034 in a game of "Ring the Bell". John rushed ahead of his teammates and crossed the finish line first; however, he was befuddled to learn that his team had lost, as Kelly and Sam came last. This taught John the importance of teamwork and the next day, his team scored higher. John soon bonded with Kelly and Sam, who would become his first and closest friends among the trainees. For eight years John was schooled in history, military strategy and tactics, and weapons, and was given extreme physical training. During his training, John used to tease Serin-019 and her habit of eating leftovers from meals of the other candidates.

John quickly proved himself to be considered one of the program's top candidates. Both Dr. Halsey and Chief Mendez identified him as one of four emerging leaders within the SPARTAN-II group, along with Kurt-051, Jerome-092, and Fred-104. Dr. Halsey believed John held both the skills and natural ability to lead the entire Spartan-II group. CPO Mendez disagreed with her assessment, instead believing Kurt would fulfill the role as team leader. John's leadership skills were correctly observed, as the result from their mission clearly solidified his role as the overall leader of the Spartan-IIs. He also became the established leader of SPARTAN-IIs Blue Team.

Taking the initiative
"No one’s being left behind. We’re going to figure a way to get all of us out."

- John assuring his comrades.

When the Spartans were eight years old, they were sent on a training mission in which they were dropped over a forest located deep in one of Reach's Highland Mountains. They were expected to get safely to their extraction vehicle, an Albatross dropship. The trainees also had instructions to leave the last member arriving behind, or their punishment would be severe. John refused. After organizing them, the Spartans looked to him as their leader. It was a role he was surprised to be given, but eventually accepted. When the group came across the Albatross, it was guarded by un-uniformed UNSC Marines, leading John to assume they were a threat. He quickly devised a plan to eliminate the hostiles, capture the dropship, and ensure the safe extraction of every team member. He also decided to take responsibility as the last arriving trainee singled out for punishment. He quickly hijacked the dropship with the help of Déjà, and attacked the guards with stones, injuring them severely. Chief Mendez was not initially pleased, feeling John had violated the boundaries of the test. However, both Mendez and Halsey quickly recognized John's initiative, and promoted him to Squad Leader. After this, despite the other Spartans rising in rank and leading independent teams, John remained the de facto leader of the Spartans as a whole.

Physical augmentation
"John-117"

- Dr. Halsey

At the age of 14, John underwent the dangerous SPARTAN-II augmentation procedures. These procedures resulted in the death of thirty trainees, with twelve more physically disabled. John was one of thirty three Spartans who made it through the process unscathed, while the wounded were sent into the Office of Naval Intelligence. Even before his cybernetic and genetic augmentation, at 14 years of age, John had a physical body of an 18-year old Olympic athlete. Far beyond the physical alternations, the enhancements boosted the Spartans reflexes, strength, enhanced eyesight, and rendered their bones nearly unbreakable. Following their treatments, John and the other Spartans were transferred to the to recover in a microgravity environment. During his first visit to the Atlas' gym, John was confronted by four ODSTs, whose sergeant then ordered the five of them into the boxing ring. In the ensuing fight, John inadvertently killed two of the ODSTs, and left the others severely injured. According to Major Antonio Silva, this incident was orchestrated by the Office of Naval Intelligence in order to test the Spartans' augmentations. While John had tried to avoid the confrontation, he nonetheless felt guilt at being forced to kill other human beings, but felt by following the orders of the sergeant he did the right thing. Then-ODST Anthony Petrosky, who witnessed the fight, would later refer to his comrades as "lambs to the slaughter"; he described John's punches as rapid-fire explosions, and that the fight was over in less than five seconds.

Following their return to Reach for further training, John and the other Spartans were soon relocated from their barracks in the FLEETCOM military complex into the abandoned titanium mines nearby. Left in the caverns virtually without equipment and pitted against Marines wearing heavy Mark I powered armor, the Spartans continuously overcame the opposition Chief Mendez planned for them using impromptu equipment and tactics.

Insurrection
John-117's first mission was against Insurrectionists within the asteroid belt of the Eridanus system, where his homeworld was located. He was shot in the side while leading his squad to capture the rebel leader Colonel Robert Watts. The official results of the mission listed eleven dead enemy soldiers and an unknown number of rebel civilians. He received a Purple Heart upon the completion of the mission.

Chi Ceti IV


Three months after Eridanus, John and his Spartans were briefed on the massacre that took place on Harvest shortly after first contact with the Covenant. A short time later, the, under the command of Captain Wallace, brought the Spartans and Dr. Halsey to the Damascus Testing Facility at Chi Ceti, where they recieved their MJOLNIR Mark IV Powered Assault Armor. When a Covenant ship, the Unrelenting, attacked the Commonwealth, John and the SPARTAN-IIs took part in their first engagement with the Covenant. The Spartans used thruster packs to launch themselves from a Pelican dropship. Each Spartan carried an ANVIL-II warhead to be used against the Covenant ship. Only two other Spartans reached the ship with John: Sam and Kelly. They entered the vessel through a puncture in its hull, caused by a MAC round from the Commonwealth. They succeeded in completing the mission and destroyed the Covenant ship, but due to a breach in Sam's armor, he was unable to leave the Covenant ship. Volunteering to stay behind and ensure the destruction of the enemy vessel, Sam was killed in the ensuing explosion. John was deeply affected at the loss of one of his closest friends. The victory showed John that the Covenant could be beaten, but only at a high cost.

Circinius IV
"Stay close to me. It's your best chance of survival."

- John-117 warning cadets about danger posed by the enemy.

In 2526, John, Kelly and Fred were sent to support Marine forces in a search-and-capture mission against an Insurrectionist leader; the skirmish quickly escalated as the Covenant's arrival forced the UNSC troops to briefly side with the rebels. Sometime later, he and Blue Team were sent to Circinius IV to reinforce the UNSC's defenses there. The Spartans eventually received a distress signal from a cadet squad pinned down at the Corbulo Academy of Military Science. John defeated the Sangheili Zealot that had been pursuing the squad, and radioed Kelly to rendezvous with him and the survivors at an extraction point up north. John, who identified himself only as "Master Chief", cleared the way to the deceased General Black's Warthog and ordered Cadet Thomas Lasky to drive.

The team was ambushed by Jackals while en route to the Pelican, causing irreparable damage to the Warthog. The team continued on foot and were relentlessly pursued by a pair of Hunters. One Hunter was killed in the ensuing battle, but in the process the squad was left with only stun rounds. John planned to put himself in the line of fire, while the cadets ran for the extraction point. However, Cadet Lasky, motivated by the death of Cadet Chyler Silva, took the Master Chief's place. The remaining Hunter fired at Lasky while John planted his last grenade inside the Mgalekgolo's worm colony. After rejoining Fred and Kelly aboard a Pelican dropship, John gave Lasky an armor fragment from the Hunter and commended the cadet on his bravery. Lasky kept the shard as a memento of the battle. He would not meet John again until 2557 on the planet Requiem.

Early to mid-war
John participated in the Harvest campaign in early 2531, where he encountered the body of fellow Spartan Daisy-023. Later that year, he led Blue Team in a raid against Camp New Hope on Victoria; Blue Team had been disrupting assets from General Howard Graves' Insurrectionists cell. John and most of the other Spartans were captured, though they were soon rescued by Kurt-051; their escape inadvertently led to Graves' death. John led Blue Team during the Battle of Jericho VII in 2535, where they killed thousands of Covenant soldiers with a HAVOK tactical nuclear weapon.

Operation: WARM BLANKET
Shortly after the Battle of Miridem in 2544, John, along with Fred-104, Kelly-087, Solomon-069 and Arthur-079, was part of a mission to rescue Dr. Catherine Halsey from a Covenant fleet. The team utilized OF92/EVA "Booster Frame" fighters, which were designed for ship boarding actions, and infiltrated the assault carrier Resplendent Fervor. While clearing the assault carrier, John encountered Sangheili Major, Thel 'Lodamee, who challenged John to an energy sword duel. Near victory, Thel was forced out of the duel when his Fleet Master separated the lower section of the assault carrier to kill the Spartans, recalling him back into the upper section. Both soldiers were left with their battle unfinished. The Spartans completed their mission and rescued Dr. Halsey, but Arthur and Solomon were killed in the battle. John was saddened by his teammates' deaths and swore he would become stronger, vowing to keep his comrades alive at all costs.

Sigma Octanus IV
By summer of 2552, he had received every medal awarded by the UNSC except the Prisoner of War Medallion. During the Battle of Sigma Octanus IV in July 2552, John led a platoon of Spartans to aid the Marine forces on the planet. John, leading Blue Team, arrived at the city Côte d'Azur to detonate a HAVOK nuclear warhead to clear Covenant forces from the city. However, the heavy Covenant presence outside the Côte d'Azur Museum of Natural History raised his suspicion, prompting him to lead Blue Team into the museum. Inside the museum, John found out that the Covenant were scanning a piece of rock while sending the information to a Covenant ship in orbit. After dispatching two Mgalekgolo guarding the rock, he took the rock and left the museum with his Spartans. John ordered the detonation of the HAVOK warhead in the city, and, along with other Spartans, Marines, and rescued civilians, returned to the, which brought them back to Reach.

Fall of Reach
"Kelly-087"

- John-117

On August 29, 2552, during the Covenant's ongoing invasion of Reach, John received an upgrade to the Mark V MJOLNIR armor as well as an upgrade to his neural interface, allowing him to support an artificial intelligence. He was then introduced to and partnered with the AI Cortana, who would become his closest friend and confidant. Before embarking on a high risk mission to capture a Covenant Prophet, the two were put through a suicidal test in an attempt by Colonel James Ackerson to defame the SPARTAN-II program. Despite the dangers, John refused to cheat the test and was determined to win it by Ackerson's rules. Despite nearly being killed, Cortana and John's teamwork allowed them to prevail in an impossible situation, the first of many such accomplishments.

On the following day, the majority of the SPARTANs were deployed to protect the generators which powered Reach's twenty Orbital Defense Platforms. John, with Linda and James, was sent to Gamma Station to destroy an unsecured navigation database onboard the prowler. If the Covenant obtained the database, they would discover the location of every human world, including Earth. The NAV database was destroyed, but Linda and James were ambushed by Covenant Sangheili. John fought one such Sangheili in close quarters combat, killing the alien before he could compromise the mission. The rest of John's team was not so fortunate; James was lost in space and Linda was critically wounded during the fighting. John saved four Marines on the station, including Staff Sergeant Avery Johnson who, unbeknownst to John, was in fact a fellow SPARTAN from Project: ORION. The team returned to the and was placed into cryo-sleep as the ship landed on and later fled Reach, and, following the Cole Protocol, jumped into slipspace. With coordinates discovered by Cortana, and in the hopes of leading the Covenant away from Earth, John would soon find himself involved in the most critical battle of the war to date.

Installation 04


"Captain Keyes"

- John-117

Arrived at Forerunner Installation 04, it soon became clear that the Halcyon-class cruiser had been followed through Slipspace by a dozen Covenant ships. These vessels engaged the Autumn and sent several capture parties to board the ship. Captain Jacob Keyes ordered John to be woken from cryosleep, and tasked him with ensuring the escape of Cortana while he crash-landed the Pillar of Autumn on the unidentified ring.

Believing himself to be perhaps the only surviving SPARTAN-II, John committed himself to the destruction of any Covenant unit unfortunate enough to encounter him. Initially, the fierce fighting on Halo was solely between UNSC and Covenant forces, but after the Covenant unwittingly released an ancient parasite, the majority of both forces became infected or destroyed.

John-117 was sent out by the Installation's monitor, 343 Guilty Spark, to retrieve the Index, an activation device for the Halo ring. Seeing the danger posed by the Flood first hand, John willfully took up the role as the Installation's Reclaimer. Upon John's return to Halo's Control Room, Cortana revealed that Halo's true purpose was not only to destroy the Flood, but prevent its spread by targeting all sentient life within its blast radius. John was then forced to disrupt Halo's firing system by disabling the ring's phase pulse generators in order to delay the Monitor's plan.

John carved a path through the three-sided conflict between the Covenant, the Flood and the Forerunners' Sentinels. Soon after, he tried to rescue Captain Keyes, but was too late. Captain Keyes had been transformed into a proto-Gravemind Flood form. After infiltrating the Covenant cruiser, Truth and Reconciliation, the Chief managed to retrieve the Captain's neural implants, which he used to activate the Pillar of Autumn's self-destruct sequence. After the sequence was aborted by 343 Guilty Spark, he proceeded to manually overload the fusion reactors, which would subsequently destroy both the Pillar of Autumn and Installation 04.

After successfully destroying the fusion reactors on the Pillar of Autumn, John-117 used a Warthog to reach the extraction point where Pelican Echo 419 was to recover him. John-117 reached the extraction point, only to witness the Pelican crashing after being shot down by a pair of Banshees. Quickly making his way to the ship's Launch Bay 7, John used the sole Longsword fighter stored there to escape Halo just before the Autumn ' s engines went critical.

Return to Reach
After the destruction of Alpha Halo, Cortana and John discovered three cryotubes floating nearby, one containing Linda-058, and retrieved them. Soon after, the Covenant flagship Ascendant Justice and several cruisers appeared from behind Threshold, having taken cover from Halo's destruction. A nearby Pelican dropship which had docked on an asteroid floating among Halo's debris field fired at the cruiser to distract it. After a successful escape from the Covenant battle group, John linked the two vessels and brought its passengers aboard the Longsword; these included Lieutenant Elias Haverson, Corporal Locklear, Warrant Officer Sheila Polaski and then-Staff Sergeant Avery Johnson. After a joyful reunion, the surviving humans aided John in capturing the Ascendant Justice. The survivors commandeered the ship and traveled to Reach to look for any Spartans who may have escaped the planet's glassing.

John succeeded in locating some of his fellow SPARTANs on Reach, along with Vice Admiral Danforth Whitcomb and Dr. Catherine Halsey. They returned to the super-carrier and linked it with the damaged UNSC frigate Gettysburg. Before traveling to Earth, they decided to head into the Eridanus system where they discovered that the rebel base, Eridanus Secundus, was still intact, now led by Governor Jacob Jiles. After receiving some repairs, they were forced to abandon the rebels in the face of a Covenant assault, and made their way toward the Covenant refit-and-repair station, Unyielding Hierophant, where an enormous fleet was poised to invade Earth.

Operation: FIRST STRIKE
"We're going to take this fight to the Covenant. We're going to launch a first strike."

- John-117 to his team about mission ahead of them.

John and remaining SPARTAN-IIs Linda-058, Grace-093, Will-043, and Fred-104, focused on finding a way to stop the Covenant from reaching Earth, the location of which had been compromised. They decided to destroy the Unyielding Hierophant in order to slow the fleet's departure. The SPARTAN-IIs infiltrated the station, and after spending eleven hours on board, they arrived at a temple where a copy of Cortana warned them of the nearby Jiralhanae guards. Linda took up a sniping position and the other four Spartans entered the temple. John was nearly killed by ambushing Brutes, but the team managed to slay their attackers quickly. Grace, however, was torn in half by three Brute Shot rounds. John activated the fail-safe on her armor, denying her body to the Covenant.

The team then sabotaged the generators in the Unyielding Hierophant, and as they escaped through a side door, the fail-safe on Grace's armor activated, disintegrating a pursuing Covenant lance. John, Fred, and Will were quickly spotted by Banshees, but their pilots were killed by Linda's precision sniper fire. The Banshees were then recovered by the Spartans. John doubled back to retrieve Linda and the team escaped by destroying a glass atrium, exfiltrating via space-walk and arrived back at the Gettysburg.

Vice Admiral Whitcomb and Lieutenant Haverson piloted the Ascendant Justice straight into the Unyielding Hierophant. Whitcomb discussed the battles of the Alamo and Thermopylae briefly with John, then prepared to fight the Covenant off while the Unyielding Hierophant's fusion reactor detonated. Each of the five hundred Covenant ships maneuvered next to the Ascendant Justice, desperately to recover a Forerunner navigation crystal. The Admiral and the Lieutenant were both killed when the station's fusion reactor exploded, annihilating 486 ships of the Covenant fleet, leaving only around a dozen intact. The paltry survivors of the Prophet of Truth's fleet would later be committed to reinforce the Prophet of Regret's botched attack against New Mombasa on Earth. John left after witnessing Whitcomb's and Haverson's sacrifice, and arrived at Earth with the last members of his team, Linda, Will, and Fred, as well as Johnson and Cortana. They also brought with them news of the Covenant's imminent invasion.

Before she left the group to embark on her own mission, Dr. Halsey presented John with a dilemma regarding the combat data on the Flood which she had analyzed. Providing the standard data set to Lieutenant Haverson would protect Sergeant Johnson from possible experimentation by ONI. However, providing him the complete data, which contained reference to Sergeant Johnson's escape from the Flood due to his Boren's Syndrome, would supposedly result in Johnson's death. While John initially gave the complete data to Haverson, after the lieutenant's self-sacrifice he decided to spare Johnson's life and destroyed the crystal containing the full data.

Battle of Earth


"Cortana"

- John-117

Aboard Cairo Station, John received the MJOLNIR Mark VI Powered Assault Armor and attended an awards ceremony with the newly-promoted Lieutenant Commander Miranda Keyes and Sergeant Major Johnson. The ceremony was interrupted by the arrival of the Covenant Fleet of Sacred Consecration, initiating the Battle of Earth. Upon discovering a Covenant antimatter charge on board Cairo Station, John fought his way through waves of Elites, Grunts, and Drones until he reached the bomb, allowing Cortana to access and deactivate it. Feeling he could put the device to better use than the Covenant, John launched himself and the charge towards a Covenant assault carrier. A timely bombing run by Longsword interceptors opened a breach in the warship's hull, allowing John to direct the bomb into the ship's fusion core. With seconds to spare, he launched himself back into space just before the vessel detonated. The quickly recovered the free-falling Spartan.

John was then deployed to New Mombasa, East African Protectorate aboard the In Amber Clad, in an attempt to board the Solemn Penance, the Prophet of Regret's flagship. Both of the strike teams' Pelican dropships were shot down by a Scarab. John and the surviving Marines fought their way to the other Pelican's crash site. After rendezvousing with Gunnery Sergeant Stacker at Hotel Zanzibar in Old Mombasa, the Master Chief destroyed Covenant infantry and armor along the shore of the city as he chased the Scarab. Upon arriving at the edge of Old Mombasa John commandeered a Scorpion Tank from Sergeant Major Johnson, which he used to punch a hole through the city's alien occupiers.

After intense fighting through numerous highway tunnels and suburbs, John reached the industrial zone, where Marines under the command of Staff Sergeant Banks were pinned down by Covenant forces. With the assistance of the Marines and a large stockpile of weapons, John boarded the massive Scarab and destroyed it from the inside. John was then transported to In Amber Clad to intercept the Prophet of Regret's flagship. When the flagship started to enter Slipspace, Lieutenant Commander Keyes was granted permission to follow it. John, and all on board In Amber Clad, were transported to Installation 05.

Installation 05


"This is not your grave...But you are welcome in it."

- Gravemind to John-117 while capturing him.

Forced to act quickly at Installation 05, John was deployed groundside in an SOEIV along with several Orbital Drop Shock Troopers. Cortana told John of the Prophet of Regret's intent to fire Halo and complete their religion's Great Journey. Recognizing the extreme nature of the threat, John was tasked with locating and assassinating Regret. He tracked the Prophet to a vast temple in the middle of a lake, but not before witnessing hundreds of Covenant vessels coming out of Slipspace, followed by High Charity, the Covenant's holy city. Quickly disposing of a force of Sangheili Honor Guards, John assassinated the Prophet and escaped the temple before it was destroyed by a nearby carrier. John jumped off the edge of the structure and into the lake below.

Losing consciousness from the impact, John was captured by the Flood's central intelligence, the Gravemind. Shortly after, the Arbiter was also captured. The Gravemind appealed to John's common interest in preventing the firing of the Halo array. Reluctantly, John agreed. The Gravemind then tasked both captives with locating the Index, sending them to the two most likely locations where it could be found. John was sent to High Charity, interrupting a sermon by the Prophet of Truth. The conflict between the Sangheili and Jiralhanae came as a direct result of John's assassination of a High Prophet, leading the Covenant to civil war.

John wasted little time in devastating the ranks of the Prophet's guardians, chasing the surviving Hierarchs through High Charity. John nearly cornered the San'Shyuum and their Brute escorts, but was too late to prevent Truth's escape. A dying Prophet of Mercy, compromised by a Flood infection form, cackled that Truth had ordered his Dreadnought to Earth where he would complete the destruction of the human race. John then crushed the infection form with his armored hand. While this act killed Mercy, he was shortly thereafter resurrected as a Flood-controlled puppet. John faced another crucial dilemma: the Covenant had the Index and could activate Halo; however, Earth's Home Fleet stood little chance of withstanding Truth's remaining forces.

Ultimately, John was forced to leave Cortana behind. In the event of Halo's activation, she would detonate In Amber Clad's reactors directly and perish with the city. John boarded the Forerunner Dreadnought, but not before promising to return for Cortana after he stopped the Covenant.

Return to Earth
"Lord Hood"

- John-117

After a vicious series of firefights, captures and escapes, John exited the Dreadnought and crash-landed on Earth, where he was found by Sergeant Johnson, the Arbiter, and the rest of their Marine squad. Johnson believed the Chief to be dead, and requested heavy lifting gear in order to recover the Spartan's body. However, John awoke to battle-ready condition only moments later, showing his incredible tolerance to pain and shock. He attempted to attack the Arbiter, believing that the Elites were still a human enemy. Johnson informed him that the two races were now allies, as the disillusioned Arbiter and the Sangheili had been expelled from the Covenant.

John and the Marines traveled through the jungle, searching for evacuation to a nearby military base. Johnson and his team split up from John and the Arbiter. The sergeant and his squad were captured by Prophet-loyalist Covenant Brutes, although they were soon rescued by John and 'Vadam. After taking heavy fire from Phantoms, a Pelican dropship evacuated the team to a UNSC base known as Crow's Nest.

The hidden facility soon came under attack, but not before Fleet Admiral Terrence Hood told John his plan to counterattack the Covenant forces above and surrounding the excavated Forerunner artifact near Voi. Lieutenant Commander Keyes decided to evacuate all troops before Truth could launch his assault. John, Thel and the remaining UNSC Marines defended the base during its evacuation, planting a massive bomb to destroy the base along with the invading Covenant forces. The Master Chief fought his way through dozens of Jiralhanae warriors, escaping the explosion in an elevator. He met up with several Marine survivors underground, and they escaped the base and headed for the city of Voi along Tsavo Highway, crushing Covenant resistance on their way.

At the Battle of Voi, John dashed towards what was believed to be the Ark. Instead, the artifact opened a slipspace portal to the Ark. With Marine support, John and Thel 'Vadam destroyed three Anti-Air Wraiths, a Scarab, and a Covenant anti-aircraft battery, allowing Lord Hood's remaining frigates to fire upon Truth's Dreadnought. Unfortunately, MAC rounds had little effect on the Forerunner Dreadnought, and Truth fled through the Portal with his remaining loyalist forces. The UNSC remained behind on Earth to determine their next move.

Just as the battle seemed over, a Flood-infested Covenant warship crash-landed in Voi. John, and his allies fought to contain the Flood infection, eventually destroying the infected warship. During the battle, Shipmaster Rtas 'Vadum came to aid the UNSC. He deployed a Special Operations Sangheili strike team through orbital insertion pods, assisting John as he attempted to recover a fragment of Cortana hidden aboard the vessel, who he learned was on the crashed vessel. Aided by the unexpected appearance of 343 Guilty Spark, John retrieved the damaged data device and was brought aboard 'Vadum's flagship, Shadow of Intent. The Sangheili were able to stop the Flood infestation by glassing the city and its surroundings, much to Hood's anger.

The Sangheili and the UNSC watched Cortana's recording, which contained a warning that High Charity, now overwhelmed and controlled by the Gravemind, was heading for Earth. However, she offered hope, hinting at a way to stop the Halos from firing and to neutralize the Flood. Convinced of the reliability of Cortana's message, John resolved to journey to the Ark, while Hood mobilized remaining UNSC forces on Earth. John accompanied a joint UNSC-Sangheili task force through the portal aboard the to the Ark.

Installation 00
Recognizing the fate of all life within the galaxy was at stake, the UNSC-Sangheili task force was determined to stop Truth from activating the remaining six Halos at any cost. The infantry strike team descended in Pelicans and Phantoms while the Shipmaster's fleet fought a 3:1 battle against an armada of Brute controlled ships. John landed on the surface of the Ark, eliminating Covenant loyalists in the area to secure a landing zone for UNSC frigate, and to find the Ark's Cartographer. Traveling in Scorpions, Warthogs, and captured Prowlers, John and other Marines located the Cartographer and learned that Truth was in the Installation's Citadel, a structure where the entire Halo Array could be activated. John then escaped from the Cartographer and proceeded to assault the fortress. After his arrival to Installation 00, John-117 began to discover a number of terminals containing ancient Forerunner communications logs, as well as direct messages from the Forerunner ancilla Mendicant Bias.

John-117, Thel 'Vadam, and a squad of Marines were assigned to separately attack three barrier towers, which were emitting a protective shield around the Citadel. Although John and 'Vadam managed to deactivate two of the towers, Sergeant Johnson was captured at the third, spared only to activate the Halos from the Ark's Citadel. John, 'Vadam, and the Elites deactivated the last tower, lowering the shield. Just as the Shadow of Intent was about to destroy the Citadel, the Flood-controlled High Charity exited Slipspace, bringing the Flood into the conflict and disabling the Shadow of Intent.

After defeating the last remnants of the Covenant forces around the Citadel, including two Scarabs, John and 'Vadam entered the Citadel. Although Miranda Keyes had forced her way in, breaking through the central window with her Pelican, she was soon surrounded. Knowing that only a Reclaimer could activate the Halo array, Johnson demanded that Keyes kill him, and then commit suicide to prevent galactic extinction. However, Keyes hesitated for a split second, during which Truth shot and killed Keyes with a Spiker. Truth then forced Johnson to begin the activation sequence for the array. In an unexpected turn of events, John and 'Vadam again made a temporary alliance with the Flood to stop the activation of the Halos. Truth's final unit of personal guards were crushed by the unlikely allies. As John and the Arbiter reached the Prophet, it was clear the San'Shyuum was already succumbing to the parasite. Thel 'Vadam executed the last of the High Prophets with his energy sword, while John deactivated the rings.

The Gravemind then betrayed John and 'Vadam, laughing as it had successfully used the pair again for its own ends. After fighting past waves of Flood, the two escaped with their lives. As they were leaving the Citadel, John saw a vision of Cortana that led him to the exit. There, he learned her plan: a replacement for Installation 04 had been built by the Ark, but was not yet connected with the rest of the Array. Since the Ark and the ring were so far from the inhabited galaxy, John decided to activate Installation 04B and destroy the Flood once and for all. But first, he headed to the remains of High Charity to keep a promise to Cortana.

"John-117"

- Cortana

On High Charity, John cut his way through hordes of Flood, taunted with images of Cortana falling into rampancy and by threats from the Gravemind itself. He finally reached the failing AI, on the verge of succumbing to the Flood's influence. After recovering her storage module, Cortana readied the Activation Index from the first Installation 04. John then destroyed the holy city by overloading its backup generators. On his way out, Cortana detected a friendly contact, which turned out to be Thel 'Vadam. High Charity exploded as the trio narrowly escaped on a Pelican.

Activating the Halo
The final mission of the war for John, 'Vadam, and Cortana was to destroy the Flood forever by activating the replacement Installation 04. The three landed on the Halo, discovering that the Gravemind was already trying to rebuild itself on the Installation. Flood dispersal pods released combat forms against John and the Arbiter, forcing them to fight their way up to the Control Room, where the ring could be activated. During the battle, Sergeant Johnson arrived and assisted the Chief.

After defeating the Flood forces around the Control Room, 343 Guilty Spark unlocked the door to the interior. Once inside, however, Guilty Spark realized that the team intended to fire the Halo before it could be completed, which would destroy the ring. Unable to cope with losing a second installation, 343 succumbed to rampancy. The AI mortally wounded Sergeant Johnson, and then turned on the Spartan.

"You are the child of my makers. Inheritor of all they left behind. You are Forerunner. But this ring...is mine."

- 343 Guilty Spark, betraying the Master Chief

John stood his ground, even after being hit by several energy blasts, and fought against Guilty Spark with all of his strength. Although the Monitor seemed to be invulnerable, Johnson shot the Monitor with a Spartan Laser, temporarily distracting him. He then handed John his weapon who destroyed Guilty Spark once and for all. Avery's injury was fatal, and he requested that his friend "send [him] out with a bang," after handing over Cortana's data chip. His last words were, "Don't ever let her go."

Cortana then activated Installation 04B, and the survivors fled to the Forward Unto Dawn onboard a Warthog, fighting the Flood and local Sentinels on the way. The team boarded the Dawn and escaped the firing and destruction of ring and the Ark. However, the Slipspace portal the frigate opened could not sustain itself under the stress, and its closure severed the ship in half, sending 'Vadam to Earth. John and Cortana were left drifting in unknown space.

Missing in action
"Were it so easy..."

- Thel 'Vadam, on the "death" of John-117

John and Cortana were presumed dead after several months of searching by ONI's director, Admiral Parangosky. The forward half of the Forward Unto Dawn, bearing the Arbiter, crash-landed on Earth. Lord Hood commissioned a memorial near Mount Kilimanjaro in Africa in honor of UNSC service members lost during the war. John's Spartan tag was carved onto the memorial by an unknown party and was accompanied by the improper insignia of the Master Chief Petty Officer of the Navy.

Stranded in space
"Wake me... when you need me."

- John's last words before entering cryostasis

John-117 and Cortana managed to survive the explosion of Installation 04B in the remaining cargo portion of the Forward Unto Dawn, but it was nearly powerless and could not be properly navigated. Cortana, relieved that John had survived, explained this to the Chief, and that it could take years before anyone could discover their distress signal. In a similar conversation to one after the destruction of Installation 04, Cortana listed what John had done and told him, "It's finished," and this time, he agreed with her. John entered a cryotube, at which point Cortana stated that she would miss him. John replied her to wake him when she needed him.

In 2556, while still stranded in space, Cortana attempted to talk to John while he was still asleep. Unable to get a response from him, she recounted the history of the galaxy, seemingly unaware that John could not hear her, and showing major signs that she was descending into rampancy.

Requiem and the Didact
"Cortana"

- John-117

In July 2557, nearly five years after John went into cryo-sleep, the aft half of the Forward Unto Dawn entered orbit above Requiem, a Forerunner shield world. As Covenant remnant forces near Requiem began to board the Dawn, Cortana awakened John from cryosleep. With Cortana's assistance, John fought off the intruders across the ship and used one of the ship's nuclear missiles to destroy an incoming Covenant cruiser. Shortly afterward, however, Requiem's access gateway opened, pulling the remains of the Dawn, as well as any Covenant ships in immediate proximity, into the interior of the shield world. Having crashed on Requiem, John took notice of Cortana's escalating signs of rampancy and she explained that her condition may be reversible if they managed to get to Earth and find Dr. Halsey in time. Fighting their way through numerous Covenant forces occupying the structure, John was attacked by advanced Forerunner defense drones which Cortana identified as Prometheans. Evading or destroying pursuit, John attempted to warn the approaching of the dangerous gravity field that had disabled the Forward Unto Dawn.

After John disabled two energy pylons preventing them from contacting Infinity and attempted to use the supposed relay satellite in Requiem's core to establish contact, it became clear that a great threat had been imprisoned within Requiem. Instead of contacting the Infinity, John had accidentally released the Didact, an ancient Forerunner warrior, from his Cryptum. Easily disabling John with his powerful abilities, he declared the return of the Forerunners as the galaxy's rulers and saviors. Humanity remained weak and unworthy in his eyes of inheriting the Mantle. Having always revered the Forerunners as gods, the Covenant quickly swore alliance to the Didact and his armies.

Narrowly escaping the collapsing core facility, John and Cortana translocated to the planet's surface only to find their warning to the Infinity came too late. The massive warship crashed nearly 80 kilometers away, with a massive force of Covenant and Prometheans closing on their position. John was successful in regrouping with a group of Marines and SPARTAN-IVs, led by Commander Thomas Lasky, who John had previously met on Circinius IV over thirty years earlier. Recognizing the Chief immediately, Lasky asked John and Cortana to clear a landing zone so that Infinity's ground forces could fall back to the ship which had fallen under siege. Commandeering a Scorpion tank, John led the attack to the crippled vessel alongside Commander Sarah Palmer's Spartans. Using the UNSC's latest weapon, the Mantis walker, John rallied a force of nearby Marines and regained control of the ship's interior. After reinitializing the ship's secondary MAC guns and missile batteries, the tide turned in the UNSC's favor and the Didact was forced to retreat.

Conflicting loyalties
"The Didact has to be stopped. If you won't do that... I will."

- John-117 to Cpt. Del Rio before disobeying his order.

With a momentary lull in the fighting, John was called to a strategy meeting with Andrew Del Rio, Captain of the Infinity. Skeptical of the threat of the Prometheans, Rio ordered an immediate attack on a Forerunner gravity well preventing the ship from leaving. A strike force of Spartans led by John was deployed with a Mammoth ultra heavy ground vehicle supporting the attack. Facing daunting odds, the UNSC was able to defeat a large armored strike force of Covenant and Prometheans and disabled the gravity beam. Diverted to an underground facility along the way, John was confronted with a vision from the Librarian, who warned him of the Didact's plans to enslave humanity with a device known as the Composer. The Librarian also provided John with a gift: a medical treatment to counteract the Forerunners' devolution of the human genome, and a means to resist the effects of the Composer.

Regrouping aboard the Infinity, Captain Del Rio dismissed the threat of the Prometheans and prepared the ship to depart the system. Defying direct orders, John took the increasingly unstable Cortana and departed the Infinity. Armed with a Pelican gunship provided by Commander Lasky, John launched several attacks on support pillars providing the Didact's Cryptum with shields and power, with the goal of preventing him from leaving the planet and attacking Earth and other colonies. John's attempt to stop the Didact ultimately proved unsuccessful, as the Didact managed to leave Requiem aboard his vessel, escorted by a flotilla of Covenant ships. Stowing away aboard a Lich, Master Chief pursued the Forerunner to Ivanoff Station, a UNSC research base orbiting Halo Installation 03 where the Composer was kept. Dr. Sandra Tillson, a lead researcher aboard the base, helped guide John to the artifact amidst a swarm of Covenant attackers. Despite John reaching the artifact first, the Didact was successful in obtaining the Composer and immediately tested the device on the crew of the station, completely destroying their bodies and assimilating their minds to power additional war machines. However, John survived, thanks to the genetic enhancements imposed by the Librarian.

Battle aboard Mantle's Approach
"Cortana"

- John-117

With the Didact approaching Earth, planning to imprison all of humanity into digital form, John pursued the Promethean aboard an F-41 Broadsword fighter on the outer hull of the Promethean's ship. As the ship exited slipspace near Earth, John was surprised to find the Infinity and the rest of the Home Fleet ready and waiting for the Didact. John was able to destroy the ship's point defense guns, giving Infinity the chance to punch through the vessel's hull. Entering the breach, John fought his way to the Forerunner's location. Despite the UNSC's best efforts, the Didact began to fire on Earth with the Composer, annihilating the population of New Phoenix, Arizona. Armed with a HAVOK warhead, John confronted the Didact for the second time. While John was unable to hurt the Forerunner with conventional attacks, the dying Cortana disabled the Didact's armor and immobilized him with hard light shackles. With the last of his strength, John used a pulse grenade to destroy the Forerunner's armor, sending him down into a slipspace rupture beneath the Composer. With time having already run out, John detonated the nuclear bomb manually as a desperate last resort.

Using the last of her power, Cortana was able to save John from the blast, saving his life at the cost of her own. The two had one final conversation, with John remarking that he was supposed to have protected her. Cortana insisted that they were supposed to protect each other, and did. Smiling and seeming at peace, Cortana welcomed John home, and then faded away completely. Left adrift in space, John was recovered by a UNSC search-and-rescue team shortly afterward. Later, John spoke with (now Captain) Lasky about the loss of his close friend and companion. Aboard the Infinity, John rejoined Palmer and the other Spartans, and had his MJOLNIR Mark VI armor removed for the first time in several years.

The Composer's Forge
"Chief, is there anything you'd like to advise us on right now?"

- Fred-104 to John-117 upon arrival to Composer's Abyss

On July 25, 2557 John was debriefed by the UNSC Security Council, though this questioning session as well as his survival were kept secret from Doctor Halsey. John confirmed that Cortana and the Composer were both destroyed over Earth, but he was unable to confirm the Didact's death. With there being no proof of a living Forerunner, the Council decided to tell the general public that the attack on New Phoenix was caused by the Covenant remnants and ended by the return of a hero, the Master Chief. Following his meeting with the Security Council, the Master Chief met with Lord Terrence Hood. Hood asked the Master Chief if he could advise a team on Installation 03 to investigate the loss of contact with a science team escorted by Spartan Black Team on the ring. The Master Chief then reunited with Blue Team, consisting of Fred-104, Kelly-087, and Linda-058.

John and the rest of Blue Team took a Longsword fighter to Gamma Halo and landed in near the science team's camp. There, the Spartans found the corpses of both the science team and Spartan Black. After being attacked by Promethean Knights, Blue Team discovered the former location of the Composer and within, the Composer's Abyss, a facility used to store the Composer's victims. The Spartans entered a slipspace portal at the end of the Abyss and were teleported to the Composer's Forge, housing six new Composers, where they were confronted by the Didact and his Promethean constructs. During the battle, 859 Static Carillon, the Forge's monitor, transported Installation 03 over the Forge by the Didact's request. The Didact subsequently took one of the Composers and departed for the Halo, intending to use the ring to eradicate humanity. Infuriated by the Didact bringing his Prometheans to the Composer's Forge, Static Carillon allied with the Spartans and escorted them back to the portal, holding off the hordes of Promethean machines.

Blue Team returned to the surface of Gamma Halo from the Composer's Abyss, arriving just in time as the Didact's new Composer rose from the pit. John fell behind while the Didact attacked and prepared to kill the others, starting with Kelly. Before he could do so, the Master Chief sneaked behind the Didact and stabbed him in the eye with his combat knife. Intending to correct his mistake of not having killed the Spartan when he had the chance, the Didact grabbed John by the head, lifted him in the air and squeezed, cracking his visor. However, the rest of Blue Team intervened, prompting the Didact to throw John aside. The Forerunner quickly disabled all four Spartans, but Static Carillon arrived and teleported the Didact into the Halo's control room before he could finish them off.

After recovering, John picked up the ring's Activation Index the Didact had dropped and intended to confront the Forerunner in the control room while the rest of the team returned to their Longsword. Using the Index to override the system's safeties, the Master Chief gave control of the Halo to Static Carillon who then ejected the section of the ring housing the control room, causing it to plunge toward the planet below. The monitor teleported John away just as the segment struck the Composer's Forge and the Didact was digitized by the Composers. John and Static Carillon materialized aboard Blue Team's Longsword, where the monitor bade farewell to the Reclaimer before departing to take Gamma Halo to an undisclosed location.

Self-reassignment
"Kelly-087"

- John-117

John returned to Earth with Blue Team where he was debriefed by Fleet Admiral Hood. While Lord Hood believed the Didact to be dead, the Master Chief considered it safer to call him "contained". Hood ordered John and the other Spartans to take a leave from combat, but upon returning to his team the Master Chief instead told them they were embarking on a new mission — evidently one of his own making. Blue Team then departed for their new activities; their whereabouts in the coming months would remain classified. After their departure, the Master Chief's behavior was discussed by two high-level individuals within ONI, who deemed his self-reassignment a predictable consequence of his nature and unwavering dedication to his career.

Eight months after the Didact's defeat, John and Blue Team were dispatched to investigate the abandoned ONI research facility. During the mission, John was confronted with an ominous vision of Cortana warning him that the "Domain was open" and that the "Reclamation was about to begin". Not long after this, John and Blue Team would apparently go AWOL.



Apparent treason


John-117 and the rest of Blue Team discovered that an extremist organization known as Sapien Sunrise was planing an attack on Richard Sekibo on Biko. As a peace conference on Biko between the UEG and Sangheili representatives was coming to an end, John entered the embassy and instantly killed a member of Sapien Sunrise who was disguised as Richard Sekibo's bodyguard. A firefight began, in which a total of eighteen human lives were claimed. John fled the embassy alongside the Sangheili delegation, which he escorted to safety. Outside the embassy, the rest of Blue Team was waiting in an evac ship for John. Unfortunately, Sekibo was killed and John was unable to save him. His corpse was left behind in a field near the embassy on Biko. The next day, local officials discovered a signal beacon that led them to the body of Sekibo. After this event, the UEG and Biko government covered it up by making it appear that John had killed authorized bodyguards and Sekibo. This false story was spread throughout the inner colonies. The media started referring to John as "The Fallen Spartan". As Benjamin Giraud prepared to expose the cover up, and reveal the atrocities committed by the people behind the SPARTAN-II Program, the UEG and Biko undercut him by radically reversing their claims, admitting and denouncing the involvement of Sapien Sunrise in the attack, utterly discrediting Giraud. Even Senator Andrew Del Rio, who had condemned the Master Chief in an official statement, reversed his position and took some immediate leave.

The Guardians
Sometime before October 27, 2558, John and the rest of Blue Team partook in a mission to find the. Departing from a D79-TC Pelican Blue Team managed to infiltrate the Argent Moon by shooting out one of the windows, subsequently causing many Sangheili part of Jul 'Mdama's Covenant to be sucked out into the vacuum. During a fight with a Mgalekgolo John was separated from Blue Team. While alone John started to experience visions from the Domain, with the image of Cortana telling him that Meridian is next and the reclamation is about to begin. With Covenant reinforcement incoming John was forced to destroy the Argent Moon and flee with the rest of his team in a Prowler. Despite receiving orders to return to Infinity John decided to refuse and take the Prowler and Blue Team to Meridian in order to beat the other Spartan team sent there.

Shortly after the UNSC declared him AWOL, Fireteam Osiris, a Spartan-IV unit led by Spartan Jameson Locke, was sent to recover him. Osiris consulted John's "old friend", Arbiter Thel 'Vadam, for the Spartan's whereabouts on Sanghelios some time after John and Blue Team evidently visited the city of Sunaion, which was home to a Forerunner Guardian.

Personality
"Our duty as soldiers is to protect humanity, whatever the cost."

- Master Chief about what it takes to protect human lifes

Until the age of six, John lived a normal life with his family on the colony of Eridanus II. His conscription into the SPARTAN-II program was to shape much of his personality in the years to come. However, despite his difficulty relating to non-SPARTAN personnel, John nevertheless showed great depth of character throughout his many years of service.

As with all Spartans, John strives to win at any situation, at all costs. Although the drive to win was ingrained to the Spartans as part of their indoctrination, John appears to have possessed such an inclination even prior to his conscription; as a child, he would win at any game he played, including chess, gravball or King of the Hill. He is extremely determined to complete any mission at hand, and often disregards his personal safety to do so. He is also noted for his exceptional luck, which, along with his combat skills and unyielding persistence, has allowed him to emerge victorious from situations many would consider impossible. Because of his many years of constant combat and military conditioning, John is not as emotional or sensitive as he once was, especially to fear. Although he is not devoid of fear, he simply acknowledges the feeling and puts it aside. He is calm in the face of danger but not foolhardy, as demonstrated during his first encounter with the Gravemind, when he warned the Arbiter that his arrogance was likely to get him killed.

John is generally stoic and taciturn, but not devoid of a sense of humor. He often makes dry remarks about the situation in hand; however, this seems to be more frequent when interacting with Cortana than anyone else, such as the other Spartans. He does not see himself as a superior being and fears for the lives of others before his own, putting himself in harm's way for the safety of civilians, and fellow soldiers, and does not judge others. Indeed, he is known to show an exceptional care for soldiers under his command and has shown great respect for the baseline humans he has fought alongside. An example of this is during the Battle of Installation 04. When making his way up to the Silent Cartographer, two Helljumpers, PFC Hosky and another Corporal, were killed by two Hunters. Afterward he regretted their loss, blaming himself for their deaths. This, and his reaction to Johnson's death on Installation 04B show that he does exhibit care and sympathy for soldiers under his command, even if he does do a good job of concealing his feelings. He was also impressed by the humans who comprised his team following his escape from Installation 04, including Sheila Polaski and Corporal Locklear, regarding the latter "as much a warrior as any Spartan".

John is also known as a man of his word and will strive to keep any promise he makes, even at great personal risk. As he was forced to leave Cortana behind on High Charity, John promised to come back for her after dealing with the Prophet of Truth. Cortana chided him not to make a promise when he knew he couldn't keep it. However, despite incredible odds, John did keep his promise, as he fought his way through the Flood into High Charity to retrieve her. Upon finding her, Cortana was in a weak and damaged state. Unfazed, the Master Chief told her, "You know me. When I make a promise..." to which Cortana replied, "You keep it." This encouragement gave her the strength to compose herself after enduring the mental tortures of the Gravemind.

John's unfaltering, determined nature also serves to mask his feelings on many occasions, as he prefers to devote all attention to the goal at hand. He is cautious and observant, only making changes in his plans if they are of the utmost necessity. John realizes his duty as a Spartan is to serve and help those in need, and can work professionally with anyone he is sent into battle with. Although John has difficulty understanding the 'undisciplined' lifestyle of civilians, he is fiercely protective of their lives and humanity as a whole. The mass slaughter of civilians at the hands of the Covenant was enough to drive even the stoic John into a cold rage. After the massacre on Draco III, John and his Spartans remained on-site until every Covenant soldier responsible for the atrocity was dead.

John greatly dislikes being kept in the dark, ambushes and fighting human soldiers. Once, when cornered by four large ODSTs in a gym, he did his best to avoid a confrontation. In the end, he was forced to defend himself with lethal force. While killing Covenant never placed a burden of guilt on John, ending the lives of fellow human beings was something he never felt comfortable remembering. As a soldier, John knows when it is appropriate and inappropriate to fight, and has great control over his emotions thanks to a clear state of mind. Due to his augmentations, he reacts much faster than an average human, seeing events at a fraction of normal speed. It is almost a clairvoyant state of mind, and as a result of this, has an acute intuitive insight and perception of any situation combat or non-combat. He has been known to have vivid and long-enduring memories of the past, such as in dreams. No matter how well-adjusted he is, however, John always seems to need to have a quiet place away from crowds after a battle in order to feel at peace.

While reflecting on his life during his battle with the Didact John stated that he did not remember anything from his childhood from before his conscription: not his name, his family, his home, except the King of the Hill game he played with the other children in his school's playground. Through thirty years of warfare he was always prepared to die in battle, but when he was about to die by Didact's hand on Gamma Halo, he discovered he was not ready to die. After defeating the Didact, John continued to obsessively embark on new battles even after receiving an R&R order from Lord Hood.

When Lord Hood offered John a commission, even suggesting he could be conferred the rank of admiral, the Master Chief jokingly replied, "The Admiral doesn't have quite the same ring to it".

Relationships
"When you first came here, you fought the trainers when they took this away from you — broke a few fingers as I recall...It has an eagle on one side. That bird is like you — fast and deadly."

- CPO Mendez presenting to John an ancient silver quarter during their last meeting

John does not open easily to strangers, and is withdrawn even by Spartan standards; he seems to prefer being referred to as "Master Chief" by civilians, and has shown an aversion to taking his helmet off in the presence of others unless necessary. Friendships are made for life, however—once given, his trust is forever, one example being Cortana, whom he initially doubted. Like most Spartan-IIs, he thinks of Doctor Catherine Halsey as a nearly mother-like figure, and holds a deep personal respect for his trainer and mentor SCPO Franklin Mendez. The Spartans, Cortana, Dr. Halsey, and SCPO Mendez, being the only family he really ever had, assume a larger-than-life importance for John-117.

John formed close friendships with the other Spartans he grew up with since his childhood, most notably Samuel-034 and Kelly-087, his first friends within the group. While still feeling the loss of comrades deeply, he has grown more accustomed to combat than most soldiers. Nevertheless, he was deeply affected by the deaths of each of the Spartans, particularly Sam. He was also saddened by Linda-058's apparent death aboard Gamma Station and was greatly relieved after Dr. Halsey successfully resuscitated her. However, having accepted the responsibility of command for the SPARTAN-IIs, he maintains a certain professional distance to his comrades and mostly keeps his feelings to himself to maintain his authority.

Cortana
In a strange twist of fate, one of John's closest friendships was with the AI Cortana, a construct "born" from the mind of Dr. Halsey herself. Despite some initial hesitation towards working with an AI out of fear of conflicting directives, John and Cortana quickly formed a formidable team. After a near-fatal training exercise masterminded by ONI Colonel Ackerson, John realized that Cortana would be a great help instead of a liability. Their relationship evolved from a partnership to a close friendship over the course of the Battle of Installation 04, probably due in part to the amount of time the two spent with each other. During their adventures, John showed absolute trust in Cortana, believing in her when even Lord Hood was unsure of her reliability, even willing to trust her enough to risk Earth on her word that she had a way to stop the Flood. Years later, on Requiem, he went as far as to disobey a direct order to give her up for decommissioning. The two also had similar personalities: they both had a propensity to blow things up, with John commenting he wasn't sure which one of them was better at it. The pair also enjoyed executing dangerous plans. After Cortana explained to John his strategy to use a disabled bomb to blow up a Covenant carrier was crazy, he offered to leave her behind. Instead, she quipped, "Unfortunately for us both, I like crazy." Cortana ultimately sacrificed herself to save him and John was clearly devastated by her death.

Thel 'Vadam
John and Thel 'Vadam's first meeting on Delta Halo was hostile, with the Arbiter continually referring to the Spartan as "Demon" and John's insistence that the San'Shyuum were making a "big mistake" by activating the Halo rings. Upon their next meeting on Earth, John was quick to try and kill the Sangheili before Johnson stopped him. They remained initially wary of one another, but learned to trust each other in combat against the Covenant and the Flood. Thel proved his trustworthiness to John through actions such as assisting him in the rescue of Sergeant Johnson, or counseling his fellow Sangheili not to glass all of Earth after the Flood outbreak at Voi. When they reached the Ark, the two's reliance on each other was cemented, and John demonstrated his respect for Thel by allowing him be the one to kill the Prophet of Truth. The Arbiter also came to his aid on High Charity despite having little need to do so, and chose to fight with John to the end in his efforts to stop the Flood and consoled him on Johnson's death. 'Vadam was the last one to see John alive before the latter went missing after the war, and afterward expressed to Lord Hood mild doubt that John might be dead. 'Vadam would later refer to John as a "friend", and upon learning that he was still alive following the events on Ealen IV, Thel believed that he was the key to the galaxy's future.

Age and appearance
John's age is affected by the same ambiguities as all beings who undergo extended voyages through space. Though he is chronologically 47 years old as of mid-2558, he has spent much of his life in cryosleep, particularly when he spent almost five years adrift aboard Forward Unto Dawn. Cellular activity is slowed to near standstill in cryosleep, effectively halting the aging process. As a result, John's biological age is significantly less than his age as measured by Terran chronology.

John has "...short hair, with serious eyes, a firm mouth, and a strong jaw." His skin is unnaturally pale since he has spent most of his life in his armor. He rarely shows his face to anyone but his closest acquaintances, reinforcing his reputation as a nearly mythic soldier. Shortly before his abduction at the age of six, John was "a typical six-year-old male, with tousled brown hair and a sly smile that revealed a gap between his front teeth".

Equipment
Throughout his career, John has shown a preference for the standard-issue set of the given Mjolnir armor generation used at the time. His Mjolnir armor is invariably colored olive green with a gold visor, which has made his appearance iconic among humans and Covenant alike. At some point during his four-year cryosleep aboard the Forward Unto Dawn, Cortana used nanomachines to repair John's MJOLNIR Mark VI armor. Cortana also rewrote the suit's firmware, altering the HUD as well as improving the suit's shield-recharge rate and its compatibility with Covenant and Forerunner armor plugins. His upgraded suit displays the Braille characters"117" on the left of the breastplate.

After the Skirmish on Installation 03, John received an upgrade for his Mark VI armor, bringing it into the GEN2 line of Mjolnir PAA. The armor still looks like his updated GEN1 Mark VI, the most prominent difference being a redesigned bodysuit. His armor also now lacks the prominent gash on the chestplate and his helmet is intact again after the Didact severely damaged it during Blue Team's battle against him on Installation 03.

Production notes

 * John is the protagonist and main playable character throughout the core of the Halo series. He is voiced by Steve Downes in the original trilogy, the Reclaimer Saga, Halo: Reach's Firefight mode, and the audio version of "Palace Hotel". In the Halo Legends shorts "The Package" and "Odd One Out", John is voiced by David Wald. In Halo 4: Forward Unto Dawn, he is physically portrayed by Daniel Cudmore, who is known for portraying the mutant Colossus in the X-Men film series, while provides his voice. Bruce Thomas provided John's motion capture performance in Halo 4 and apparently served as the model for his face in the game's Legendary ending.
 * John-117 is likely named for Sylvester Stallone's character John Spartan, Prisoner #117, from the 1993 action film Demolition Man. Spartan is placed in cryostasis before awakening decades later, much as John-117 is introduced emerging from cryosleep in Halo: Combat Evolved.
 * John appears as an Easter egg in Halo: Reach, asleep inside a cryo pod in the Pillar of Autumn's hangar.
 * Late in the development of Halo: Combat Evolved, (when the game was known simply as Halo) Microsoft urged Bungie to change the main character's title from "the Master Chief" to "the Commando", as they felt that it better suited the tone of the game.
 * In Halo 5: Guardians, John-117's character-specific base attributes are increased melee damage and faster shield and health regeneration rates. His default weapons loadout includes an MA5D assault rifle, an M6H magnum, and two fragmentation grenades.

Trivia

 * At some point during the Human-Covenant War, a John-117 action figure was made. Gabriel Thorne's grandmother bought one after he was recruited into the SPARTAN-IV program.
 * A tower in the shape of John's helmet can be found on Mars in Bungie's Destiny.
 * Fable II makes a reference to the Master Chief with a character of legend named "Hal", also called the Minstrel Chief. The armor featured (clearly inspired by Halo's MJOLNIR Powered Assault Armor) is known as "Hal's Armor". A sword resembling the Energy Sword is also featured in the game, known as "Hal's Sword". In addition, with the Special Edition, the player can obtain the title "Master Chief" for their hero for free from any title vendor.
 * A wax sculpture of the Master Chief is on display at Madame Tussauds in Los Angeles and Amsterdam. He is the first video game character to receive a Madame Tussaud's wax sculpture.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Conversations from the Universe
 * Halo Graphic Novel
 * The Last Voyage of the Infinite Succor
 * Armor Testing
 * Halo: Ghosts of Onyx
 * Starry Night
 * Believe
 * Diorama
 * Halo Landfall
 * Halo: Last One Standing
 * Halo: Uprising
 * Halo 3
 * Halo Wars
 * Halo: Helljumper
 * Halo Legends
 * Origins
 * Homecoming
 * Odd One Out
 * The Package
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Mona Lisa
 * Palace Hotel
 * Human Weakness
 * Halo: Reach
 * Data pads


 * Halo: Fall of Reach
 * Boot Camp
 * Covenant
 * Invasion
 * Halo: Glasslands
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo: The Thursday War
 * Halo 4: Forward Unto Dawn
 * Scanned
 * Halo 4
 * Spartan Ops
 * Halo: Initiation
 * Halo: Escalation
 * Halo: Mortal Dictata
 * Halo: Broken Circle
 * Halo: Nightfall
 * Halo 2 Anniversary
 * Terminals
 * Halo: New Blood
 * Hunt the Truth
 * All Hail
 * The Cost
 * Halo: Spartan Strike
 * Halo: Hunters in the Dark
 * Halo: Fleet Battles
 * Halo: Last Light
 * Halo: The Fall of Reach - The Animated Series
 * Halo 5: Guardians