Master Chief

Master Chief Petty Officer John-117 is a SPARTAN-II commando of the UNSC Naval Special Warfare Command who became one of the most important UNSC heroes during the Human-Covenant war. With nearly thirty years of active duty he has become one of the most decorated war veterans in the United Nations Space Command, earning every known UNSC medal with the exception of the Prisoner of War Medallion.

Childhood and SPARTAN training
John was born in about 2511 and 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 dream during cryo-sleep aboard the UNSC Pillar of Autumn, John recalled that his mother was "kind and smelled of soap," and that she had "large eyes, a straight nose and full lips." The would-be UNSC Marine Lieutenant Parisa was a childhood friend of John's who John once saved from drowning at Lake Gusev; John thereafter promised to marry and protect her. Parisa's father shot a photo of the two soon after that Parisa kept as a memento long after she thought John had died.

Dr. Catherine Halsey identified John as an ideal physical and mental candidate for the 150-strong preliminary pool of the SPARTAN-II Program when he was six: he stood a head taller than the majority of his schoolmates, had greater physical proportions, and possessed greater strength, superior reflexes, and an aggressive drive for success. When Dr. Halsey and Lieutenant 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 and which was the side of the eagle. John was the first candidate Dr. Halsey and Lieutenant Keyes studied. Later that same year, John and 74 other six-year-old children were "conscripted": they were covertly kidnapped from their homes and replaced with flash clones, all of which would later die of natural causes to cover up the kidnappings. John, along with the other candidates, was taken to the planet of Reach. Dr. Halsey informed them of the SPARTAN-II Program and how they would be "the protectors of Earth and all her colonies." The next morning John discovered his service tag, stitched into his training uniform, and his new name: John-117.

John began a new life. He trained with other Spartans under Chief Petty Officer Franklin Mendez. For eight years he learned history, military strategy, weapons and received physical fitness training. Early on, he bonded with Kelly and Sam, who would become two of the few close friends that he would ever have.

John quickly proved himself to be one of the program's top candidates during his training. 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 Frederic-104. Dr. Halsey most strongly expressed her belief in John by stating that he had the skills and natural ability to lead the entire SPARTAN-II group. However, Mendez disagreed and instead believed that Kurt would fulfill that role.

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 snow-filled mountain ranges and expected to get safely to their extraction Pelican dropship. The children also had instructions to leave the last child arriving behind lest they receive painful punishment; John-117 knew, however, that he could not do that. After telling the Spartans where to meet, the Spartans looked to him as their leader, a role he was initially surprised to receive but eventually accepted. When the group came upon the Pelican, it was guarded by armed men. Those men were actually UNSC Marines but were not in uniform; the Spartans therefore mistook them for a hostile threat. John showed early acumen in critical thinking and tactics, not wishing to take for granted that guards would be friendly toward them. He came up with a plan to take the men down, capture the dropship, and ensure the safe extraction of every team member, as he made sure he was the last person aboard. To do so he ended up hijacking the dropship with the help of Déjà and beat down the men with stones, causing severe injuries among the Marines. Chief Mendez was visibly displeased by John's having attacked his Marines and leaving no-one behind, but both Mendez and Halsey recognized John's initiative and promoted him to squad leader. Thereafter, despite other Spartans' rising in rank and at least a couple rising to lead their own teams, he remained the de facto leader of the Spartans as a whole.

John's leadership skills were correctly observed: the result from their mission clearly solidified his role as the overall leader of the SPARTAN-IIs. He also became the established leader of the SPARTAN-II Blue Team. John-117 fighting ODST teamJohn-117 fighting a group of ODSTs on the UNSC Atlas.

At the age of fourteen, John underwent the dangerous SPARTAN-II augmentation procedures. These procedures killed 30 and physically disabled 12 of the Spartan trainees. John was one of 33 Spartans who survived the process unscathed, while the rest who could still operate were moved to positions in the Office of Naval Intelligence. At only fourteen years old, John was said to have the body of an eighteen-year old Olympic athlete; the augmentation process hastened their reflexes, increased their strength, enhanced their eyesight, and rendered their bones nearly unbreakable. After their augmentation procedures, John and the other Spartans were transferred to the Atlas in order to recover in a microgravity environment. Four ODSTs confronted John during his first visit to the Atlas' gym; their sergeant then ordered the five of them into the boxing ring. In the ensuing fight, John killed two of the ODSTs, and left the others severely injured, an incident which quickly blossomed into major resentment for the whole SPARTAN program throughout the Marine Corps. According to Major Antonio Silva, "people who invented John" orchestrated this incident in order to test the Spartans' augmentations.

Early military career
In 2525 John was given his first mission against insurrectionists in the asteroid belt of his home Eridanus system. He was shot in the side without heavy injury while leading his squad to capture United Rebel Front leader Colonel Robert Watts. The mission casualty list was 11 dead rebel soldiers and an unknown number of rebel civilians. John received a Purple Heart.

Three months thereafter, John and his SPARTANs were briefed on the massacre that had taken place on Harvest shortly after first contact with the Covenant. The UNSC Commonwealth, under the command of Captain Wallace, soon brought the SPARTANs and Dr. Halsey to the Damascus Testing Facility at Chi Ceti, where they received the MJOLNIR Mark IV Powered Assault Armor. When a Covenant vessel, the Unrelenting, attacked the Commonwealth, John and the SPARTAN-IIs engaged in their first battle with the Covenant. The SPARTANs used thrusters to launch from a Pelican dropship. Each SPARTAN carried an ANVIL-II Air-to-Surface Missile to destroy the Covenant ship. Only John, Sam, and Kelly reached the ship.

They entered it through a hull breach from a MAC round from the Commonwealth and succeeded in completing the mission and destroyed the Covenant ship, but a breach in Sam's armor from Covenant retaliation fire from Covenant forces prevented him from leaving the enemy vessel; he made the most of his misfortune by ensuring that the ship exploded. Sam's death profoundly affected John: it proved to him that the Covenant could be defeated, but only at the cost of many lives.

John and the remaining SPARTANs fully employed their MJOLNIR armor to fight the Covenant Empire for the next 27 years. Halo 4 Forward Unto Dawn Chief GestureJohn during the Battle of Circinius IV.

In 2526, a Covenant attack on the Corbulo Academy of Military Science sparked the Battle of Circinius IV. The UNSC had suspected the safety of the planet for several days and garrisoned it with Marines and ODSTs. The Academy was destroyed almost as soon as the attack began, but Blue Team was able to deploy to the surface undetected mere hours later. John fought to the Academy ruins and protected the cadets by fighting off Covenant forces while waiting for evacuation by Kelly-087 and Frederic-104. He first met Thomas Lasky, who was a young cadet at the time. John-117 Mark IV LegendsJohn as the operation kicks off.

Main article: Raid on the Third Fleet of Glorious Consequence

In 2544, John, along with Fred-104, Kelly-087, Solomon-069 and Arthur-079, participated in the Raid on the Third Fleet of Glorious Consequence to rescue Dr. Catherine Halsey. The UNSC deployed a prowler stealth corvette to transport SPARTANs who would infiltrate the Covenant fleet as it was forced to exit slipspace in order to traverse a stellar magnetic field. The SPARTANs were given ten minutes to complete the rescue mission or be caught in the annihilation of Third Fleet of Glorious Consequence, likely only possible through the use of a prototype NOVA Bomb. The team infiltrated the fleet with OF92/EVA "Booster Frame" fighters, which were designed for ship boarding actions. Solomon detected Catherine Halsey's beacon from a Covenant CCS-class Battlecruiser that had its hangar bay shields down. John-117 intuitively voiced his concern about this irregularity but chose to disregard it. Solomon infiltrated the vessel with cover from Kelly and quickly discovered the source: a Covenant antimatter charge.

Kelly escaped the immediate detonation due to John's warning, but Solomon was vaporized. A further scan resulted in positive readings from all enemy vessels from which John deduced that Catherine was held on the Covenant flagship at the heart of the fleet. The SPARTANs then successfully fought their way through the Covenant's Seraph formations, and sheared through the massive vessel's hangar bay energy shields with a large barrage of explosive ordnance, gauss cannon rounds, and their own Booster Frame's as projectiles to infiltrate the Covenant CAS-class assault carrier, the Resplendent Fervor. Upon entry John, Kelly and Fred protected themselves with a Bubble Shield. The clearing smoke revealed surrounding Covenant forces in the hangar bay.

With three minutes remaining, John and the SPARTANs sprinted through the collapsed Bubble Shield and down the corridors of the vessel, effortlessly slaughtering Covenant infantry as Frederic-104 breached doorways with a Spartan Laser. Ambushed by Sangheili Energy Swordsmen, Frederic locked the nearest doorway behind John and Kelly to engage them with combat knives alone. The Supreme Commander Luro 'Taralumee initiated a scuttle of the rear of the ship to escape the SPARTANs. Forced to leap from the section disconnected from the Assault Carrier, Kelly grabbed John's hand and threw him forward using inertia to increase his speed toward the escaping ship but thus threw herself back into space: John reached the ship.

After rescuing Catherine Halsey from her cryonic stasis pod, John encountered Sangheili Major Thel 'Lodamee, who deflected John's barrage of assault rifle fire and challenged him to an Energy Sword duel. Thel disarmed John and kicked him to the ground, but he was forced out of the duel when his Fleetmaster separated the lower section of the Assault Carrier to kill the SPARTAN, thereby pulling Thel back into the upper section; both combatants survived unscathed. John and Halsey descended into the ship and commandeered a weaponless Covenant shuttle craft. A Seraph formation attacked them on exit, but a Seraph commandeered by Fred and Kelly annihilated the enemy fighters and recovered John and Halsey along with fire support from their prowler. John's teammate's deaths deeply saddened him: the operation saw more SPARTAN-IIs killed in action than any before the Fall of Reach. John vowed to become stronger and never allow such a loss to happen again.

John served in over 200 campaigns against the Covenant Empire over the next 27 years. These included the Harvest Campaign, the Battle of Jericho VII, where he and a handful of Spartans destroyed a force of over a thousand Grunts, and the Battle of Sigma Octanus IV, in which John and his Blue Team detonated a HAVOK Nuclear Warhead to clear Covenant forces from the city of Côte d'Azur. By summer of 2552, he had received every medal awarded by the UNSC except the Prisoner of War Medallion: Covenant forces usually take no prisoners, and John would not allow himself or any other SPARTAN-II to be captured by the enemy.

Fall of Reach
The Fall of Reach, though brief, was of great significance for John. Here,he received the MJOLNIR Mark V Powered Assault Armor, which improved his strength and reaction time more effectively than his older Mark IV suit. He was also introduced to and partnered with the AI Cortana, who would become a close friend and ally to him. In the first test of their partnership, the two were put through a practically suicidal test in an attempt by Colonel Ackerson to get rid of John. 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 had them pass the test in an early show of the incredible partnership the two would come to develop. After Reach came under attack by a massive Covenant armada, the majority of the Spartans, led by Fred S-104, went to the planet's surface to protect the Orbital Defense Generators which powered the planet's twenty Orbital Defense Platforms. John, with Linda and James-005, were sent to Reach Station Gamma to destroy an unsecured NAV database on board the UNSC Circumference. If the Covenant obtained the database, they would discover the location of every human world, including Earth; the location of Earth by then was still a closely guarded secret. The NAV database was destroyed, but Linda and James were ambushed by Covenant Sangheili; James was lost in space, and Linda was critically wounded. John saved four other Marines on the station, including Staff Sergeant Avery Johnson. The team returned to the UNSC Pillar of Autumn and was placed into cryo-sleep as the ship landed on, then fled Reach and, following the Cole Protocol, jumped into Slipspace with coordinates deduced by Cortana from constellation data retrieved earlier, in hopes of leading the Covenant away from Earth.

Installation 04
Once the ship had arrived safely at Installation 04, it emerged that the UNSC Halcyon-class light cruiser UNSC Pillar of Autumn had been followed through Slipspace by around a dozen Covenant ships, who ultimately engaged the Autumn and sent several boarding parties to board the ship. Captain Jacob Keyes ordered John to be woken from cryosleep, and tasked him with ensuring the escape of Cortana (who was the ship's AI), while he crash-landed the Pillar of Autumn on the unidentified ring.

John escaped the Pillar of Autumn on a life pod, and rallied Marines to fight against Covenant forces stationed on the ring. Cortana found out that Captain Keyes had been captured and was held prisoner on the CCS Truth and Reconciliation, by way of hacking into the Covenant battlenet. John joined the strike team that was sent to rescue Captain Keyes, where he learned that "Halo" was a super weapon. The Captain gave John new orders, to locate the map room that pinpointed the location of Halo's Control Center. When John was finished, he was dropped off in the first of three snowy chasms leading towards the Control Room. During the long trek, he encountered Fire Team Zulu and they assisted him in securing the first and second chasms.

Initially, fighting on Halo was between UNSC and Covenant forces, but after Covenant forces had unwittingly released an ancient parasite, the majority of both forces were infected, and the fighting shifted to combating the new enemy.

Flood infestation of Installation 04
John-117 was sent out by Installation 04's Monitor, 343 Guilty Spark, to retrieve the Index, an activation device for the Halo ring that John-117 is led to believe would destroy all Flood forms within a large radius. Upon John's return to Halo's Control Room, Cortana revealed that Halo's true purpose is to destroy all sentient life forms in the galaxy to starve the Flood, not to kill the Flood themselves. John was then forced to disrupt Halo's firing system by disabling Halo's Phase Pulse Generator in order to delay the Monitor's plan.

John soon joined the three-sided combat among 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 Truth and Reconciliation, John 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 proceeds 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 would pick him up. John-117 reached the extraction point, only to witness the Pelican crashing into the Autumn's hull after being shot down by a pair of Banshees. John quickly diverts his escape route towards the ship's hangar bay, which housed a Longsword fighter. Only a handful of UNSC forces survived, including Lieutenant Elias Haverson, Corporal Locklear, Warrant Officer Sheila Polaski, then-Staff Sergeant Avery Johnson, Private First Class Chips Dubbo, and then-Staff Sergeant Pete Stacker.

Journey to Earth and Operation: FIRST STRIKE
After the destruction of Alpha Halo, Cortana and John-117 fled through space in the Longsword they had escaped in. He discovered three cryotubes floating nearby, one containing Linda-058, and retrieved them. Soon after, the Covenant's flagship Ascendant Justice came into the system along with a few cruisers, some of which had possibly escaped Halo's destruction and called the flagship to Threshold. 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. The crew of the Pelican then helped John in capturing the Ascendant Justice; the human survivors then traveled to Reach to look for surviving Spartans. John eventually located some of his fellow SPARTAN-IIs on Reach, along with Vice Admiral Danforth Whitcomb and Dr. Catherine Halsey. They returned to the ship and linked it with the UNSC frigate UNSC Gettysburg. They began to travel toward Earth and soon discovered a base belonging to the Eridanus Rebels, led by Governor Jacob Jiles.

After receiving some repairs, Dr Catherine Halsey surreptitiously leaves with Kelly-087 to an unknown location aboard Governor Jacob Jiles personal ship, at the time docked with the UNSC Gettysburg/Ascendant Justice. The remaining UNSC forces 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. Just before the slipspace jump, Corporal Locklear inadvertently commits suicide while distorting the Forerunner Crystal, recovered by Dr Halsey from underneath the ruins of CASTLE base. Halsey gave it to the Corporal, shortly before her departure, intending he is to destroy it rather than let it fall into the hands of the Covenant.

John faced a dilemma regarding the combat data on the Flood which Dr. Halsey had given him. 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 result in Johnson's death.

John and the few remaining SPARTAN-IIs: Linda-058, Grace-093, William-043, and Fred-104, focused on finding a way to stop the Covenant from reaching Earth, the location of which had been discovered. They decided to destroy the Unyielding Hierophant. The SPARTAN-IIs infiltrated the station; after spending eleven hours on board, they arrived at a temple, where a copy of Cortana warned them of the Jiralhanae guards stationed at the temple. Linda took a sniping position, and the other four Spartans entered the temple. They were ambushed by Brutes, and John was nearly killed, but the team managed to kill their attackers. Grace, however, was killed by three Brute Shot rounds. John activated the fail-safe on her armor, denying her compromise by the Covenant.

The team sabotaged the generators in the Unyielding Hierophant; as they escaped through a side door, the fail-safe on Grace's armor activated, disintegrating a Covenant lance. John, Fred, and Will were quickly spotted by three Banshees, but their Sangheili pilots were killed by Linda's sniper fire. The Banshees were then captured by the Spartans. John doubled back to retrieve Linda, who killed four more Banshee pilots who were attempting to kill John. They then escaped by destroying a glass atrium, and arrived back at the UNSC Gettysburg.

Vice Admiral Whitcomb and Lieutenant Haverson piloted the Ascendant Justice straight toward the Unyielding Hierophant. Whitcomb discussed the battles of the Alamo and Thermopylae with John, then prepared to fight the Covenant off while the Unyielding Hierophant's fusion reactor detonated. Each of the 500 Covenant ships maneuvered next to the Ascendant Justice. The Admiral and the Lieutenant were killed when the fusion reactor exploded, annihilating 486 ships of the Covenant fleet, leaving only around a dozen intact; these ships later joined the Prophet of Truth's rebuilt fleet in the attack 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.

Battle of Earth
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 Fleet of Sacred Consecration, initiating the Battle of Earth. John successfully repulsed Covenant boarders from the station. Upon discovering a Covenant Anti-Matter Charge on board Cairo Station, John fought his way through waves of Elites, Grunts, and Drones until he reached the bomb and allowed Cortana to access and deactivate it by transferring her back to his suit. Afterwards, she chose to rejoin him despite his offer for her to remain on the station. He used the charge against the Covenant by launching himself and the device, via decompression of one of the station's launch bays, towards an Assault Carrier. A timely strike by Longsword interceptors opened a breach in the warship's hull, allowing John to direct the bomb into the ship's fusion core. He then proceeded to use the blast from the bomb to launch himself back into the UNSC In Amber Clad.

John was then deployed to New Mombasa, East African Protectorate aboard the UNSC In Amber Clad, in an attempt to board Solemn Penance. Both of the strike teams' Pelican dropships were shot down by a Scarab. John and the surviving Marines on his team fought their way to the other Pelican's crash site. After rendezvousing with Gunnery Sergeant Marcus Stacker at Hotel Zanzibar in Old Mombasa, John-117 destroyed Covenant units along the shore of the city as he chased the Scarab. Upon arriving at the edge of Old Mombasa, John received a Scorpion Tank from Sergeant Major Johnson.

After fighting through numerous highway tunnels and suburbs, John reached the city center, where Marines under the command of Staff Sergeant Marcus Banks were pinned down by Covenant forces. With the assistance of the Marines and a large stockpile of weapons, John boarded the Scarab and was able to destroy it and the Covenant forces protecting it. 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 brought to Installation 05.

Installation 05
Forced to act quickly once at Installation 05, John deployed groundside in an SOEIV along with several Orbital Drop Shock Troopers. This team was tasked with locating and assassinating the Prophet of Regret. Cortana informed John of Regret's intent to fire Halo as soon as possible. He tracked the Prophet of Regret to a temple in the middle of a lake, but not before witnessing hundreds of Covenant vessels coming out of Slipspace, followed by High Charity. He quickly dispatched the Prophet of Regret, and escaped the temple shortly before it was destroyed by an overhead cruiser. John jumped off the edge of the structure and into the lake below.

Losing consciousness and being unable to swim in the lake, he was captured by the Flood's central intelligence, the Gravemind. Shortly after, Thel 'Vadam was also captured. The Gravemind appealed to the common interest of the Flood and the humans share, that of not wishing the Halos to be fired. John agreed. The Gravemind then tasked both captives with locating the Index, sending them to the two most likely locations. John was sent to High Charity, interrupting a sermon by the Prophet of Truth. The conflict between the Sangheili and Jiralhanae was beginning, leading the Covenant on the path to civil war: John was caught right in the middle.

John chased the surviving Hierarchs through High Charity, eventually catching up to the Prophets and their Brute escorts. However, only a dying Prophet of Mercy, who had been compromised by a Flood Infection Form, was left to tell him that Truth was heading to Earth. John faced another crucial dilemma: the Covenant had the Index and could activate Halo; however, Earth's defenses stood little chance of withstanding Truth's reassembled fleet. Ultimately, John followed the latter priority, forced to leave Cortana behind so that if Halo were activated, she would detonate In Amber Clad's reactors, not wanting to risk detonating them remotely. John boarded the Forerunner Dreadnought, which was bound for Earth, but not before promising to return for Cortana after he stopped Truth.

Return to Earth
After a series of firefights, captures and escapes, John exited the Dreadnought and crash-landed on Earth, within an East African jungle, where he was found by Sergeant Johnson, the Arbiter, and the rest of their squad. Johnson believed John 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 the enemy. Johnson informed him that the two races were now allies, as the disillusioned Arbiter and the Sangheili had defected 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 soon captured by loyalist Covenant Brutes, although they were rescued by John and Thel 'Vadam. After taking heavy fire from Phantoms, a Pelican dropship evacuated the team to a UNSC base known as Crow's Nest.

The base soon came under attack, but not before Fleet Admiral Terrence Hood told John his plan. Lieutenant Commander Keyes decided to evacuate all forces, many of whom were injured. 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. John-117 fought his way through many Brutes, 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 Jefe Maestro H3John-117 in Tsavo Highway. the Battle of Voi, John pushed through many Loyalist forces as he made his way to what was believed to be the Ark. Rather, this turned out to be a device that opened up a portal to the Ark. With Marine support, John destroyed three Anti-Air Wraiths, a Scarab, and a Covenant Type-27 Anti-Aircraft Cannon, allowing Lord Hood's remaining frigates to fire upon Truth's Dreadnought, with little effect. Truth then activated and fled through the Portal with his remaining Loyalist forces, while the UNSC remained behind to determine their next move.

Just as the battle seemed finished, a Flood-infested Covenant warship crash-landed in Voi. John, Arbiter, and the remaining Marines fought to contain the Flood infection, learning that the only way to contain the Flood was to destroy the 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 was sent to retrieve Cortana from the cruiser, as it was believed that she was on board. Aided by 343 Guilty Spark, John retrieved a damaged data device and was brought aboard 'Vadum's flagship, Shadow of Intent. This data turned out to be only a message, rather than Cortana herself. The Sangheili were able to stop the Flood infestation by glassing the city and its surroundings, much to Hood's displeasure.

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, with information of a way to stop the Halos from firing and neutralize the Flood threat. 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 UNSC Forward Unto Dawn to the Ark.

Installation 00
The Sangheili carried UNSC forces through the Slipspace portal which led to the Ark. The team was determined to stop Truth from activating the remaining six Halos. They descended in Pelicans while the Shipmaster's fleet fought hard against the Brute ships. They flew to the surface of the Ark to eliminate the Covenant in the area, to secure a landing zone for Forward Unto Dawn, 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. John then escaped from the Cartographer and proceeded to assault the fortress.

John-117, The Arbiter, and a squad of UNSC Marines were assigned to separately attack three Barrier Towers, which were emitting a protective shield around the Citadel. Although John and Arbiter managed to deactivate two towers, Sergeant Johnson was captured in the battle, being spared to serve as a Reclaimer. John, Arbiter, 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 battle and disabling the Shadow of Intent.

After defeating the last remnants of the Loyalist forces around the Citadel, including two Scarabs, John and the Arbiter entered the Citadel. Although Miranda Keyes had forced her way in, breaking through the central window with her Pelican, she was soon surrounded. As she hesitated before killing Johnson and herself, Truth shot and killed Keyes with a Spiker. Truth then forced Johnson to begin the activation sequence. In an unexpected turn of events, John and the Arbiter made a temporary alliance with the Flood to stop the activation of the Halos. The final Loyalist defenses were crushed by the Flood as John and the Arbiter reached Truth, who was already being infected by the Flood. Then the Arbiter executed him with his energy sword, while John deactivated the rings.

The Gravemind then betrayed John and the Arbiter, laughing as it had succeeded in preventing its own destruction. After fighting past waves of Flood, the two escaped. As they were leaving the Citadel, John saw a vision of Cortana that led him and the Arbiter to the exit. There, he learned her plan: a replacement for Installation 04 had been built by the Ark, and was not yet connected with the rest of the Array. Since the Halo was so far from the inhabited galaxy, John decided to activate the ring and destroy the Gravemind, but first headed to the remains of High Charity.

On High Charity, John battled his way through hordes of Flood, being taunted with images of Cortana falling into rampancy and by threats from the Gravemind. He finally reached Cortana, who still had the Activation Index from the first Installation 04. John then destroyed the 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.

Firing Installation 04B
The final task for John, Arbiter, and Cortana was to destroy the Flood by activating the Installation 04B. The three landed on the Halo, finding that the Gravemind was 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 to assist John in battle.

After defeating all Flood forces around the Control Room, 343 Guilty Spark unlocked the door to the Control Room. Once inside, however, Guilty Spark realized that the team intended to fire the Halo before it could be completed, which would destroy the ring. After mortally wounding Sergeant Johnson, he then turned on John.

“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 John-117

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

Cortana then activated the second Installation 04, and the Arbiter and John fled to the Forward Unto Dawn on board a Warthog, fighting the Flood and local Sentinels on the way. The team boarded the Dawn and escaped the firing and destruction of the replacement Installation 04. However, the Slipspace portal which was opened for them could not sustain itself under the stress, and its closure severed the ship in half, sending Thel 'Vadam to Earth. John and Cortana were left drifting in space towards Requiem.

Missing in action
John and Cortana were presumed dead when they did not make it back to Earth. 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 servicemen lost during the war. As there were no pictures to remember him by, John's SPARTAN ID number, 117, was carved onto the memorial by an unknown party, and the UNSC Master Chief Petty Officer of the Navy insignia patch was taped beside his ID number. Ironically, he and a few other Spartans were the only ones truly Missing In Action.

Stranded in space
John 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, without airlocks or a bridge, could not be properly navigated. Cortana, relieved that John had survived, explained this to John, and that it could take years before anyone could discover their distress signal. In a similar conversation to one at the end of Halo: Combat Evolved, Cortana listed what John did and told him "it's finished," and this time, John agreed with her. John placed himself in a cryotube, at which point Cortana said, "I'll miss you." John replied with "Wake me… when you need me.", and went into cryosleep.

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
Four years, seven months, and ten days later in 2557, the Forward Unto Dawn arrives at the Forerunner Shield World named Requiem. Cortana wakes John-117 from cryosleep when they are scanned by Requiem. Shortly after, the Dawn is boarded by Covenant forces seeking to deny them access to the shield world. After shooting down a Covenant cruiser, Requiem opens and draws both the Dawn and the Covenant fleet into the shield world. John miraculously survives the impact and lands on Requiem, where Cortana reveals that she is descending into rampancy. John's undying loyalty to Cortana leads him to promising Cortana he'll get her back to Earth and getting Dr. Halsey to fix her, however Cortana states she cannot recover from rampancy. John presses on and navigates the wreckage, and while doing so, finds the transmission of the UNSC Infinity, although faint.

Cortana tells John they need to hijack a Covenant ship and as they close in on the Forerunner Facility, the Infinity's signal clears up enough to hear a word. In the Forerunner facility, John and Cortana find a Localized Cartographer, revealing to John and Cortana that they are on Requiem. When John asks Cortana to find out what the Covenant Remnant are searching for, the console is locked up by an unknown source. They reactivate the Cartographer, and after doing so the transmission from the Infinity is picked up again, much clearer than before. Cortana attempts to contact the Infinity, however to no avail. She then suggests for John to use the Cartographer to find the Infinity's location. The Cartographer refuses initially, although soon points John to Requiem's core, which he doubts is an accurate estimation of the ship's whereabouts. Cortana states that the planet is hollow and that somebody could have got deeper into Requiem than them. Afterwards she suggests to take a portal to the core from a Terminus on the far side of the complex. John fights his way to the Terminus, which is situated atop a Tower.

Upon reaching it, Cortana attempts to open a portal to the point of the Infinity's transmission location. When she tries to do so, The system responds with the Forerunner symbol for Reclaimer. She tries again. However, when the portal opens, a large number of Promethean Knights spawn around them, but hesitate to engage in combat. John then jumps into the portal, evading the AIs. They exit the portal somewhere near the core, close to a console. The "satellite" in the centre of the core is amplifying the Infinity's transmission, but two beams coming from it are interfering with the "satellite". Cortana then opens another portal to an area near the first pylon, where John encounters the Prometheans. He fights through them and takes down the pylon, which clears up the signal even more. Upon returning to the console, several Covenant Remnant ships exit slipspace at the core, and start heading toward the second pylon. John then portals near to this point, fighting his way to and disabling it, making the transmission clean. John is then contacted by the Infinity's captain, who picked up John's IFF Tag. Cortana attempts to warn the Infinity not to enter Requiem, but the signal received by Captain Del Rio is faint, thus the ship is ordered to move faster, endangering the crew greatly.

John is advised to head to the satellite quickly by his companion, and when doing so finds the Covenant and the Prometheans in a firefight. He makes his way through them and upon reaching the "satellite", Cortana tells John to touch two pillars with the Reclaimer symbols on them. In order to contact the Infinity and to warn its captain, the SPARTAN does so. Instead of being a satellite, the machine is revealed actually to be the Ur-Didact's Cryptum, with him needing a Reclaimer to be released. The Didact is then let out from his spherical cell after one-hundred-thousand years of imprisonment. Stating that Humans were not fit to uphold the Mantle, he calls The Librarian 'meddlesome' in attempting to protect humans and by simply waving his hand regains control of all the Prometheans; turning their Hardlights orange instead of blue. He dismisses John and Cortana, by throwing the Master Chief into a far-away wall,rendering him less of a threat as he tries to recover from the impact, he then tries to avoid the didact's jump into slipspace, but is left unconscious with the didact leaving the core, destabilizing it in the process. John awakens and escapes the planet's core by Ghost, using it to jump back to the surface just in time to watch the Infinity crash, the Didact following to scan it.

Rescuing the UNSC Infinity
Following the Didact, John fights his way through countless Prometheans in a jungle on Requiem, eventually encountering Commander Lasky and Commander Palmer as well as several Spartan-IVs and marines. Fighting alongside the marines through more Prometheans, John eventually discovers several Knights commanding Covenant forces. After extracting via Pelican, John joins forces with his successors as they fight their way to the Infinity in a scorpion, where Captain Del Rio orders him to take a Mantis and deal with the Didact's cryptum outside the ship. Fighting his way through dozens of Prometheans and Covenant soldiers, John makes it to the outer hull of the ship where, after fighting off several waves of Banshees and Phantoms, he activates one of the Infinity's MACs where it and the rest of the ship's defenses repel the cryptum. After meeting up with Del Rio, John and Cortana tried to convince the captain of how much a threat the Didact really is, only for their efforts to be in vain as Del Rio was more concerned with having the Infinity escape and send a report back to FLEETCOM. When John attempted to make it a point about the Didact's vulnerability, Del Rio retorted with a veiled insult about John being the final SPARTAN-II before the bridge.

Destroying the Gravity Well and escaping Requiem
John was later deployed along with Gypsy Company to destroy the gravity well keeping Infinity inside the planet. Hitching a ride with a Mammoth, he worked his way down a canyon-like landscape, using a Target Locator to destroy a Particle Cannon en route. He later entered a Forerunner structure in hopes of disabling a certain restraining piece of technology, but was instead lured into what appeared to be a shaft of blue light after Cortana went missing. He was encountered by the preserved consciousness of the Librarian in Requiem's system and told of the Didact's plans to use a device known as the Composer against humanity after a remedial education on the history of the Human-Forerunner relations and the Forerunner-Flood War. In order to combat the Didact effectively, the Librarian advanced his evolutionary process to render him immune to the Composing process, soon releasing him to fend off the Didact.

John destroyed the gravity well and returned to the Infinity, where he tried to convince Captain Del Rio of the threat the Didact posed. Del Rio refused to believe it, which angered Cortana, having another fit of rampancy surprising the crew. Del Rio ordered Cortana to be decommissioned because of her outburst, only to have John take her chip away before anyone else could. Del Rio ordered for the chip to be returned only to be turned down by John, angered even further Del Rio ordered for John to be arrested at the hands of Palmer. John gives a final warning of the Didact, and leaves the bridge. Lasky decided to circumvent orders and instead give John a Pelican to help in his efforts to defeat the Didact. John left the Infinity and went to disable two towers that were generating a shield around the Didact, later attempting to use a control tower to trap the Didact inside Requiem. When that failed due to Cortana's worsening condition, John decided to hitch a ride on one of his escort Liches. Leaping from a tower, the SPARTAN skydived down to one. The Didact's Cryptum fused with a Forerunner ship, the Mantle's Approach, in the planet, and he, along with the few dozen escort Liches and, unbeknownst to him, John-117, went through a slipspace portal leading to Installation 03.

Ivanoff Station and the Composer
After traveling through the slipspace portal safely by hiding under a piece of a Covenant Lich, John-117 arrived with the Didact and Covenant Remnant forces at Installation 03. There the UNSC research facility fell under attack by the forces from Requiem. John-117 managed to enter the Lich,incapacitate the Covenant crew and take over the bridge, sending a broadcast to the station and warning them of the impending attack, telling them to have an immediate evacuation. In the middle of the message Cortana's rampancy stopped John-117's broadcast with another outburst. She ignored his command to stop the Lich from a crash course with the station and continued to ramble, causing the captured vehicle to crash into the station.

After waking up in the remains of the crash, John-117 regained communications with the station's head scientist, Dr. Tillson. He recommended for her to evacuate the station. Replying that the Covenant had taken over the landing bays, John-117 then told her to at least prepare for evacuation while he secured one. He fought his way through the station, defeating multiple Covenant Remnant squads until he eventually had cleared an evacuation point. From there he made his way to Dr. Tillson to explain the situation of the Didact's yearning for the Composer on the station. As the Composer was too large to move with anything less powerful than the biggest star ship in the UNSC, The SPARTAN asked for Dr. Tillson to give Cortana access to the station's supply manifest in order to search for a means of destroying the Composer.

Cortana managed to find a nuclear warhead on the station, and the Master Chief decided that it was the only way the Didact could possibly be stopped from taking the Composer. Telling Tillson this caused her great distress, as she had dedicated herself to researching the Composer for a very long time. However, she still gave the SPARTAN her word that she would make sure the warheads were primed for a remote detonation. Apologizing, John once again asked for Tillson to begin the evacuation.

When Tillson began this evacuation, the first evacuation shuttle was shot down by the Covenant. Cortana realized that she and John would be able to program the station's defenses to provide cover for the evacuation. Fighting his way to the defense console, Cortana's rampant outbursts continued to worsen. While Tillson's team rigged the warhead, Cortana programmed the defenses, succeeding to make them target the Covenant. The SPARTAN then went to rendezvous with Dr. Tillson, but was hindered by the Composer's location being compromised. Fending enemies off once more, the Chief told Dr. Tillson that, ready or not, he needed the weapon then. On his next broadcast to her, he received no response, and so headed back to the elevator platform to get to a cargo bay, hopefully to find the nuke and Dr. Tillson. An immense energy wave hit the elevator in mid-transport, stopping it. The Mantle's Approach then pulled the Composer away from Ivanoff Station with ease. John tried to focus Cortana on finding the Tillson.

Cortana researched Tillson's career files, stating her full name (Sandra K. Tillson), and that she was a student at Pegasi institute where she obtained a doctorate in Archaeology. Cortana soon found her on another deck in the station and confirmed her bio signature was stable. The elevator continued on its course and John-117 exited it to find Tillson and a large crowd of distressed scientists. Telling her that the Didact stole the Composer, he inserted Cortana into the system and asked to check the flight catalog for anything that can carry a payload. Tillson in confusion asks the Chief how the Didact moved the Composer, then, trembling, told him "Wait... something is happening" as the Didact charged a beam. He asked Cortana to activate the station's defenses, but they did not respond. Cortana continued to search through the catalog but found nothing. Unable to help, Cortana watched as the Composer composed every member of the science team at once, only knocking John unconscious because of his immunity to the weapon.

Infiltrating the Didact's ship
An unspecified amount of time passed before John-117 awakened and saw Cortana, distraught, sitting at the console. She asked him if he was okay and, crying, said she could hear what was left of the scientists after monitoring the data pulse. The SPARTAN clearly attempted to avoid emotional conversation, and stoically stated that they needed to move. Cortana sadly said that the scientists were gone, to which John dutifully added that more would follow if the Didact reached Earth. Cortana returned to dwell on her ensuing rampancy and how the UNSC would pair John with another AI, possibly another Cortana model if Halsey let them. He told her that he wouldn't let that happen. She ignored his stubborn optimism and desperately informed him that the new AI wouldn't be her. Beginning to power up a Broadsword in the hangar, the AI let the Master Chief know that whatever the Librarian did to John-117 worked.

John-117 made his way to the hangar, entering the pilot seat of the Broadsword, which was being armed with the warhead. He then set off from Ivanoff Station in pursuit of the Didact. Cortana stated a plan of boarding the ship and finding the bridge when the Didact began to prepare for another slipspace jump. She warned him that the Broadsword's shields were not rated for slipspace, but John replied that the Didact's were, before boosting forward to take refuge inside his enemy's shielding. The SPARTAN then started to fly along the outer hull of the Didact's ship, toward the Composer, dodging pieces of the ship as they moved and activated defenses attempting to destroy him.

During this time, the Didact broadcasted a signal, expressing his surprise and dismay at how John-117 wasn't composed and that such inoculation should not have been possible. Cortana explained that the Didact was with the Composer and that they could destroy both of them at once. John continued to fly through the outer hull of the ship until Cortana told him that they were coming out of slipspace. Communications from Earth warned them of the fleet's detection of the unknown ship. Master Chief then attempted to contact Captain Del Rio on the Infinity. Thomas Lasky, however, picked up John's transmission. John questioned him as to where the captain was, with Lasky replying that FLEETCOM wasn't happy with Del Rio abandoning the Chief on Requiem, and that he himself would have to do instead. John explained the Didact's intentions and that he and Cortana were in a Broadsword carrying a HAVOC grade payload, with the intention of destroying the Composer. Lasky had the orbiting fleet engage the Didact and the Composer.

The SPARTAN managed to fight through the remainder of the outer hull and located the Composer and the Didact. Attempting to gain access to the Composer, Master Chief was cut off from an opening to it. John informed Lasky of this, to which he recommended deactivating the shields so Infinity could make another opening. John-117 proceeded to destroy the shield and weapon generators. With the defenses down, the Infinity moved into position, using its MAC cannon to shear a path into the Didact's ship and granting John-117 an entrance.

John entered the ship, and, in an attempt to stop him, the Didact caused the pathway to close down on the Broadsword. John expertly maneuvered his fighter through the compressing pathway until it shrank to a narrow strip of white light, making the Broadsword crash. He stepped away from the destroyed hull of his Broadsword, somehow seemingly unscathed, Cortana queried John as to what his next move was. He procured the nuclear warhead and magnetically locked it to his armor, designating it as "Plan B". From there he fought his way through waves of Promethean resistance leading to the Didact. Eventually the duo reached the central control area of the Composer. The Chief then used a gravity lift to thrust himself across a void, reaching the lower floors of the control center. John accessed a terminal to try to allow Cortana to deactivate the shield the Didact deployed to protect the Composer. Cortana told him to insert her into a few terminals around the Composer so that she may the shielding around it. After fighting his way to the first generator Cortana revealed that she was going to do something that he was not going to like. Her holographic form tore into multiple copies as she ejected her rampant personality spikes into the system, in order to overwhelm and disable the shielding under the stress of the sheer amount of multiplying rampant copies. Repeating this process, John-117 moved to engage the Didact, who declared that he (John) had failed, firing the Composer onto Earth and Composing the population of New Pheonix. John went to retrieve Cortana but the Didact disintegrated the terminal, launching a desperate John backwards.

John proceeded through more waves of Prometheans Knights, whilst Cortana sent a message of text to his HUD to show that she had survived within the systems of the Mantle's Approach. He began to hear multiple strange voices from the rampant personality spikes of Cortana proclaiming their intent always to take care of him.

Locating a gravity lift, the SPARTAN was elevated to a light bridge directly connected to the Composer. He caught sight of the Didact within the orange aura above the Composer, but his enemy quickly vanished, sensing his presence. Vocally challenging John, the Forerunner claimed that the man had persisted too long offering him the opportunity to have his "resolution". John turned with a jolt to notice the Didact behind him and attempted to engage him, before being thrown back by his Forerunner enemy, having the warhead knocked away from him and sliding across the light bridge and his Battle Rifle pushed into the abyss below.

Regaining his footing, John-117 became torn between his options of charging the Didact or retrieving the warhead. He ran for the warhead but was stopped by the Didact who lifted and held him over the slipspace portal that was powering the Composer, claiming John was misguided and that humanity's imprisonment in the Composer would be a kindness. The Didact began to close his fist, exerting a crushing force on John and causing him to groan in what would be extreme pain even for a SPARTAN-II.

Before he could drop John into the abyss, the Didact was surrounded by Cortana's rampant personality spikes who emerge from the light bridge. After a short confrontation with the Didact, Cortana attacked the Didact and bound him by the arms to the bridge by using her hardlight forms. John-117 was released and crashed chest-first onto the edge of the light bridge, barely able to grab onto the ledge, with the swirling orange abyss beneath him. He climbed up the bridge and swiftly charged the Didact, plunging a Pulse Grenade into his armor. The Didact, however, broke free from Cortana's bonds and pushed him away, sending him sliding across the bridge. Freeing his other arm, the Didact began to slowly lift John into the air, with the SPARTAN exerting sounds of desperation and pain, preparing for an almost imminent demise. The grenade detonated, causing the Didact to lose focus, become seriously injured and drop John, stumbling off the bridge into the slipspace rupture below. Out of time, John painfully crawled towards the warhead, frequently crashing onto the light bridge. He prepared to make the ultimate sacrifice. Taking one final look up at Earth, John yelled in defiance to his enemy and smashed his hand on the tip of the warhead, detonating the nuclear weapon. Master Chief H4Master Chief, observing Earth.

John awakened in a strange area, surrounded by hardlight. He called Cortana's name. John received no reply, and began to look around when a blue light drew his attention. A now human-sized Cortana stepped out of a coding circle around them and slowly approached him. John asked the AI how to leave, but Cortana said that she wouldn't be coming with him this time. Stubbornly refusing to believe this, the SPARTAN ordered that they go together, and, with his voice quivering, told her, "I am not leaving you here." Cortana sadly said his name before resting her hand on his armor for the first and last time. She sighed and emotionally revealed that she had been waiting to be able to touch him. The Chief reminded Cortana that it was his job to protect her; however, she told him that it was their job to look after each other -- and that they had done so.

After briefly touching John, she then began to walk away. Choked up, he begged for her to wait. Disappearing into the data-circle and leaving behind a devastated John, Cortana was gone. The hardlight aura around him flickered and faded and the debris of the Mantle's Approach fell around him. Left drifting in space, Pelican Nine-Sixer came across and rescued him, taking him to the Infinity where he is greeted by a large force of marines and Spartan-IVs.

A brief confrontation with Lasky on the observation deck of the Infinity showed the now lonely soldier that he felt soldiers and people were two different things -- and Lasky informed him that they were not. Suddenly John came to a realisation about himself. Being brought up as a killing machine had distanced him from being a human, and he now saw that he had distanced himself from almost every other person he had ever known. He recalled what Cortana had asked him earlier, about who out of the duo was the real machine, and finally he found himself an answer: it was him.

John was next seen entering the Spartan-IV training deck aboard the UNSC Infinity, surprising most of the trainees there. He proceeded to an armor removal station where a team of scientists removed his armor, whilst the other Spartan-IVs and personnel looked on in respect and admiration. (His eyes appear if the Halo 4 campaign is completed on the Legendary difficulty.)

Subsequently, John was debriefed on his clashes with the Ur-Didact and his encounter with the Librarian. His whereabouts are currently unknown.