John-117

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John-117
Biographical information
Birthplace:	Eridanus II
Date of birth:	2511
Gender:	Male
Height:	2.08m
Hair color:	Brown
Political and military information
Spartan tag:	SPARTAN-117
Rank:	Master Chief Petty Officer

"No soldier should be honored for doing what is expected."

— John-117 to First Lieutenant Shah, Second Battle of Mombasa

John-117, often referred to as the Master Chief by other humans, or Demon by Covenant warriors, is a United Nations Space Command SPARTAN-II supersoldier.

Background

John-117 is a genetically and cybernetically augmented warrior raised from the age of six to be a Super Soldier for the UNSC. He was initially used to put down rebels and insurgents within the UNSC colonies. When the powerful alien empire known as the Covenant attacked, the Master Chief and the other Spartan-II's were given a new a priority; protection for the entire human race. Extensive surgical alteration coupled with a ruthless lifelong training regimen has resulted in the Master Chief being significantly stronger than a normal human, and his strength and fighting ability are further augmented by the advanced MJOLNIR Powered Assault Armor he wears. He is the main character and protagonist of the Halo video game series.

He has been involved in over 200 engagements in his 27-year career, and has been awarded all of the UNSC's major Decorations except for the Prisoner of War Medallion.

Biography

In his early life, John lived in Elysium City, on the planet of Eridanus II. He was large for his age at the time, approximately a foot above his school peers. John had all the genetic markers set in Dr. Halsey's original study- he was as close to a perfect subject for the SPARTAN-II program as science could determine. He was a specimen of perfect physical proportion and stunning intellect. Dr. Halsey and Lieutenant Jacob Keyes went to his colony world to study him, and were quite amazed by his reflexes, and more importantly, his luck. To determine if he would be one of the ones chosen for the program, he was asked to determine which side a flipped coin would land on. He watched the coin as it flew in the air...and caught it before it could land, having chosen which side he wanted it to be. John and the other 74 children unwillingly participating in the program were covertly kidnapped from their homes, and replaced with Flash Clones which later died of natural causes.

Training

At first, since John was used to being different and winning by himself, he couldn't understand the point of working as a team. After his first "playground" training exercise, which was to ring the bell before any other team; John, who was disappointed with his teams cooperation, went and rang the bell by himself. Unfortunately, he didn't win because he didn't ring it with his teammates. John, having lost his team dinner that night, had realized the importance of working as a team. During the next exercise his team of Samuel-034 and Kelly-087 worked together and formed a permanent friendship. From that point on, John seemed to be a leader among the Spartan trainees, and it was not long until he became the Spartans' squad leader.

Eight years into Spartan training, John underwent physical augmentation and was one of only 33 to survive the process and remain fit for combat duty. He was torn by the loss of his teammates and had trouble determining if he had spent their lives or wasted them.

During his time with the Spartans, John was deemed the "luckiest" and was chosen to be the first to test the MJOLNIR armor. He proved it's compatibility with a Spartan user to be impressive beyond anything before known.

File:01mc.jpg

Master Chief with a Shotgun, circa Halo 2.

Before the Battle of Reach, he had fought in 207 ground engagements against the Covenant, and garnered every major service medal except The Prisoner of War Medallion. It is also during this time that he is deemed the best Spartan candidate by Dr. Halsey to work with and protect Cortana. She explains that although he is neither the smartest, strongest, nor fastest of the Spartans, he is the most well-balanced, having each of those qualities in equal measure; he is also the bravest of all the Spartans and quite possibly the "luckiest" as well.

File:Control Room.jpg

Master Chief and 343 Guilty Spark in Halo's Control Room.

The Eridanus Rebellion

MCPO John-117's first mission was against Rebels in the asteroid belt of the Eridanus System, where his homeworld was located. He was slightly wounded while leading his squad to capture the traitor Colonel Robert Watts, leader of the rebels. He received a Purple Heart after the mission.

The Covenant War

Later on, he was briefed on the Covenant threat; he and his Spartans would fight at least the next 27 years against this new threat while employing the MJOLNIR Mark IV armor.

Alpha Halo

File:Chief 3.jpg

Master Chief fires his weapon

After many battles in the Human-Covenant War and surviving the Fall of Reach, he embarked with the Pillar of Autumn. The Pillar of Autumn was later attacked by the Covenant and was forced to crash land on Halo, Alpha Installation 04. In the midst of fighting the Covenant, Cortana discovered the secret of Halo while inserted into the computer in the Control Room of Halo; that it was a ring-shaped construct created by the Forerunners as a last line of defense against a new species of parasitic organisms called The Flood, which was released at some point by either the Forerunners or the constructs of the installations (343 Guilty Spark, 2401 Penitent Tangent, etc.); a majority of the Covenant Elites and UNSC Sailors and Marines who landed on Halo were infected by The Flood. Captain Jacob Keyes and a small group of Marines were the first humans to encounter the Covenant-released Flood; Captain Keyes was later captured by the Flood, soon after which he died. The Master Chief was then responsible for retrieving the Index for 343 Guilty Spark, a device which would activate Halo and destroy all Flood forms within a large radius. Later, Cortana informed him of the truth about the purpose of the installation (that it was a superweapon) that would destroy all life forms not just the Flood. This led him to keep the Index from 343 Guilty Spark as long as possible. While being attacked by many Covenant, Flood and Forerunner Sentinels, he later made his way back to the Pillar of Autumn and initiated the destruction of Halo. Very few other members of the UNSC forces survived, notably Sergeant Major Johnson.

OPERATION: First Strike

After the destruction of Alpha Halo, the Master Chief and Cortana floated in the space in the Longsword he used to escape. He discovered three cyro tubes floating nearby, one of them containing Linda, and pulled them into the fighter. Soon after, the Covenant Flagship Ascendant Justice came into the system along with a few cruisers. A nearby Pelican dropship made its presence known and fired at the cruiser to distract it. John then linked the two vessels and brought its passengers aboard to the Longsword. There were seven others that helped in capturing a Covenant ship, rendezvousing with the Eridanus Rebels, and destroying the Covenant space station, Unyielding Hierophant. Linda-058 was another Spartan on the Pillar of Autumn, stored in a cryogenic state because of the body damage she sustained when she and Master Chief destroyed the data base containing the info needed by the Covenant to find Earth. Anton and Li were Spartans that died in an explosion after repairing the engine on the captured Covenant ship, the Ascendant Justice.

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One of the many medals John has received

Also, two other Spartans, Issac and Vinh, survived the initial attack on Reach with Fred, Linda, Kelly, Anton, Li, Grace, Will and Dr. Catherine Halsey but sacrificed themselves by running into the middle of an entire battalion of Covenant troops and detonating an explosive. This selfless act destroyed the Covenant troops by more than half. Only Grace, Kelly, Will, Fred (Fredric), Linda and John were left. Dr. Halsey, head of the Spartan-II project sedates Kelly-087 and takes her on a mission that John and the others do not understand. John never knew of the others' fate. Prior to Halsey's disappearance, John faces a dilemma regarding the combat data on the Flood. Either he can give the regular data on the Flood, or give the complete data of the Flood encounter, which would condemn Johnson to death from ONI's subsequent experimentations. After the First Strike operation, John made the decision to hand over the regular data and omit the explanation for Johnson's survival. After this, the Spartans that are still alive search for a way to stop the Covenant from reaching Earth, which has been discovered. John finds a way to do so, by using his remaining squad to destroy the Covenant Battleship known as the Unyielding Hierophant. Linda, John, Grace, Will, and Fred infiltrate the ship and quickly move forward to their positions. They cross the ship over a period of eleven hours and reach a temple, where a copy of Cortana warns them of a new guard known as "brutes". Linda leaves for a sniping position, and the other four Spartans slip into the temple. They are ambushed by Brutes, and John is nearly killed. He manages to kill the single Brute attacking him, and kills the other Brutes his team is defending against. Grace however, is killed by the Brute Shot that some Brutes used. John activates the failsafe on her Mjolnir armor and they proceed to sabotage the generator in the Hierophant. As the Spartans escape out a side door, the failsafe on Grace's armor activates, disintegrating several elites and many grunts. John, Fred, and Will are quickly spotted by three Banshees. As they flee, Linda snipes all three of the elites out of their cockpits, allowing the others to take the Banshees. John doubles back to retrieve Linda, who manages to snipe four more elites out of their Banshees while the Elites try to kill John. Linda is ordered to let John find her, and sends Oly Oly Oxen Free over her COM channel. John finds her hanging upside-down off a catwalk, with a rope tied to her boot and another tied to the railing several meters above. She was hidden behind a brilliant light and in the depths of a deep shadow. She drops and lands on top of John, and they fly towards the place where Will and Fred are. They quickly escape, and arrive back at the Gettysburg. They see the Ascendant Justice being piloted by Vice Admiral Whitcomb and one of the Lieutenants straight towards the Unyielding Hierophant. Whitcomb discusses the Alamo and Thermopylae with John, then prepares to fight the Covenant off while the Unyielding Hierophant's fusion reactor detonates. Every one of the five hundred covenant ships maneuvers in right next to the Ascendant Justice, and the Admiral draws an SMG. The Admiral and the Lieutenant die, just as the fusion reactor explodes. The explosion annihilates four-hundred and eighty-eight ships of the fleet, leaving only a dozen badly damaged ships to invade Earth. John then leaves after witnessing Whitcomb's sacrifice, and arrives back at Earth with the last members of his team, Linda, Will, and Fred.

Return to Earth

File:117.jpg

SPARTAN-117

Chief's Mark V MJOLNIR armor was switched by technicians aboard the orbiting defense station Cairo to a Mark VI model. He attended a brief awards ceremony aboard the station, the ceremony then was interrupted by Covenant boarders, which he repulsed. The Master Chief then briefly participated with defense in the First Battle of Earth. After confiscating a covenant bomb that was intended to destroy the Cairo, he requests permission from Lord Hood to leave the ship to "give the Covenant back their bomb". Master Chief then drags the bomb into a Longsword hanger bay to launch it. The resulting depressurization of the hanger, causes him and the bomb to be flung into hard vacuum, where he manages to gain entrance into a Covenant Capital Ship's fusion chamber and detonate the bomb. The Master Chief then hitches a ride on the In Amber Clad and lands in New Mombasa, East African Protectorate to combat Covenant landing troops. During his descent on board Pelicans, his dropship is shot down by the Scarabs main cannon. The Master Chief is briefly knocked unconscious and has to fight his way to the other Pelicans, with the aid of surviving marines from his ship. After a rendezvous with Gunnery Sergeant Pete Stacker in the Zanzibar Hotel, in Old Mombasa, the Master Chief destroys Covenant units along the shore of the city as he chases the tracks of the Scarab. Once he arrives at the edge of Old Mombasa, he encounters a small group of marines, whose platoon as been destroyed by the Scarab. The Master Chief receives a Scorpion Tank from

Master Chief with the Covenant bomb

Sergeant Johnson. After fighting through numerous highway tunnels, he arrives in various parks outside the main city, and after fighting through those, the Master Chief finally arrives in the city center, where a group of marines, under the command of Staff Sergeant Banks were pinned down. With the assistance of the Marines and a large stockpile of weapons, the Master Chief manages to board and destroy the Scarab. The Master Chief then is transported to the In Amber Clad to intercept The Prophet of Regret's flagship. When the flagship starts to enter Slipspace, Commander Miranda Keyes then is granted permission to follow it. The Master Chief and all on board the In Amber Clad are then brought to Installation 05.

Delta Halo

In Amber Clad exited Slipspace in front of a blue gas planet called Substance, with another Halo in orbit at a Lagrange point. John helljumped down to the surface with a number of ODSTs, took control of a Covenant-held island, and killed the High Prophet of Regret, who prematurely led the Covenant fleet to Earth.

Chief and Cortana plan their hunt for the Prophet of Truth on High Charity

He was then captured by the Gravemind after barely escaping the destruction of Regret's main temple, and taken under the Library, where he met his Covenant Elite counterpart, the Arbiter. Under the directions of the Gravemind, the two set off to stop the Covenant from activating Delta Halo. John-117 infiltrated High Charity to stop the High Prophet of Truth, while the Arbiter went to stop Tartarus from activating the ring's weapons system and wiping out all sentient life within the its range.

In the end, Cortana decided that she didn't want to chance a remote detonation of In Amber Clad, and stayed aboard High Charity to ensure Delta Halo's destruction. Meanwhile, John followed Cortana's directions after Truth to a Forerunner ship (The Dreadnaught), which embarked for The Ark, which is most likely to be on Earth. Upon arriving in the Sol System, John informed Fleet Admiral Hood and the remaining UNSC forces who were still defending Earth that he intended to "finish this fight."

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Second Battle of Earth

"Radio for VTOL. Heavy lift gear. We're not leaving him here."

— Johnson, upon finding what seemed to be John's corpse

"Yeah... you're not."

— John-117, grabbing Johnson's arm

File:H3 Chief.png

Chief and a fire team of Marines take cover in a jungle.

John eventually escaped and crash landed on Earth. He was found by Sergeant Johnson, the Arbiter, and the rest of their team. At first, Johnson thought the Chief had died, though he awoke and was ready for battle again. Upon awakening, John charged the camouflaged Arbiter, thinking he was an enemy, until Johnson told him that they were allies. John and the rest of the team then traveled through the jungles on Earth, searching for evac to a nearby military base. Johnson and his team split up from John and the Arbiter, in order to prevent capture. Johnson however was captured, and the Chief was determined to rescue him. He found Johnson at a Brute encampment, where he and the Arbiter battle loyalist Covenant forces until Johnson's team was freed. They were then under heavy fire by Phantoms; however, a Pelican dropship saved them from the phantoms and evacuated the team to a UNSC base.

At the base, John met up with Commander Miranda Keyes. During a transmission from Lord Hood, the Prophet of Truth interfered with the signal and assured the UNSC they'd be defeated. Master Chief, the Arbiter and the rest of the UNSC were forced to fight and defend the base. When it was lost, they planted a bomb to destroy the base, along with members of the loyalist Covenant forces. Master Chief fought his way through many Brutes, eventually reaching an elevator to escape the explosion. He met up with several marine survivors underground, and they escaped the base and headed for the city of Voi.

Battle of Voi

"On Halo, you tried to kill Cortana. You tried to kill me!"

— Master Chief to 343 Guilty Spark

At the Battle of Voi, Master Chief pushed through many loyalist forces as he made his way to what he believed was the Ark. In actuality, it was a only a device that would open up a portal to The Ark. At the cartographer, Master Chief was able to destroy an anti-aircraft gun and allow Lord Hood's ships to fire upon Truth's defenses. Truth fled through the portal with his loyalists forces in a hurry, while the UNSC remained behind to determine their next move. Just as the Second Battle of Earth seemed to finish, a flood-infested Covenant warship crash landed in Voi. Master Chief was forced to, once again, battle the Flood and stop them from spreading. He learned that the only way to contain the Flood was to force the crashed Flood infested warship to explode.

During the battle, Ship Master Rtas 'Vadum came to aid the UNSC. He was able to fight off the Flood, as the Master Chief was sent on another task. The Elites informed the UNSC that the Flood had Cortana on that warship. Master Chief went to recover her, though it turned out to be a recorded message from Cortana. The Monitor, 343 Guilty Spark, took the message to the Shadow of Intent, where the Elites and the UNSC watched Cortana's recording. The Elites were able to stop the infestation by glassing half the continent of Africa, much to Lord Hood's displeasure.

After the meeting, Master Chief was set on heading for the Ark, along with the Elite forces, as Lord Hood held up against the remainder of the loyalist forces on Earth.

Battle of The Ark

"How close are you, Chief?"
"Not close enough…"

— Commander Keyes and Master Chief

The Elites carried the Master Chief and UNSC forces through the cartographer's portal, which led the team to the Ark. There, the team was determined to stop Truth from activating the seven Halos. Master Chief led a squad to one tower, The Arbiter to the second, and Johnson to the third, as Keyes and 'Vadum held off the loyalist starships in space.

Master Chief fought through many loyalist forces and eventually made his way to the top of the tower, where he deactivated part of the shield to Truth's location. The Arbiter soon followed, however Johnson was not responsive. He was overrun and captured by Truth. They needed Johnson to activate the rings, and so Master Chief and the Arbiter were sent to rescue Johnson and stop Truth. On the way there, the two fought Brute forces once more. During the battle, the ship High Charity teleported to the Ark, which brought the Flood into the battle as well. They managed to deactivate the third tower, but Truth already had Johnson captive.

When Master Chief and the Arbiter arrived at Truth's location, they realized they weren't close enough to stop him, since the elevator had been lifted. Miranda Keyes then forced her way into the edifice, breaking through the window with her Pelican. She managed to shotgun a Brute, but was soon surrounded. Truth killed Miranda when she hesitated to kill Johnson to stop Truth. Johnson, losing the will to fight, was then forced by Truth to activate the Halos. Master Chief and the Arbiter were finally able to make it to the top, and went after Truth. Immediately, they encountered the Flood, however, the Flood also wanted to stop Truth. And so, the final Brute defenses were defeated by the Flood as Master Chief and the Arbiter reached Truth. Truth had been infected already by the Flood, and the Arbiter killed him, as Master Chief deactivated the rings.

After the deactivation of the rings, the Gravemind revealed himself, laughing as he succeeded to prevent his own destruction. The Flood then attacked the Chief and the Arbiter. Luckily, both their skills helped them survive the attack and escape the Ark. As they were leaving The Ark, Chief saw what seemed like a vision of Cortana. He was led to the exit by her, and it was revealed that a replacement for Installation 04 had been built, apparently by the Ark. Chief was set to once more detonate the Halo, but first, he took a detour at High Charity to retrieve Cortana.

Finding Cortana

"You... found me..."

— Cortana to the Chief

On High Charity, the Chief battled through hordes of Flood forces, both hybrid and pure forms. He faced hundreds on the ship, but he eventually found his way over to Cortana's location. Finally, Chief's visions stopped, as he found Cortana and retrieved her, keeping his promise to her. The two then were once again reunited. And Cortana quoted one of her first words to John "Keep your head down...Theres two of us here remember?". The Chief made his way back through High Charity and forced the ship to explode. On his way out, Cortana detected a friendly unit helping out the Chief as he escaped. It turned out to be the Arbiter, and Cortana was surprised the two had "made nice".

As the ship High Charity was destroyed, the Flood was believed to be defeated.

Installation 04 replacement

John-117 witnesses Guilty Spark's treachery

"Halo. It's so new... unfinished. I'm not exactly sure what will happen when we fire it..."

— Cortana to the Chief, evaluating their plan to activate Halo

"We'll head for the Portal. And we'll all go home"

— Chief to Cortana

The next task of the Master Chief and the Arbiter was to destroy the Flood by activating the replacement Installation 04. The two landed on the Halo with their Pelican they escaped with from High Charity. Master Chief and the Arbiter were surprised when the Flood was not defeated, but instead trying to rebuild itself on the Halo. Flood dispersal pods released many of the Flood into battle against Master Chief and The Arbiter, forcing them to fight their way up to the tower where the ring would be destroyed. During the battle, Sergeant Johnson arrived on the Halo aboard the UNSC Forward Unto Dawn.

File:Chief and Arbiter Escape Halo.jpg

John and the Arbiter escape.

Johnson helped the Chief and the Arbiter fight their way on the Halo using a Spartan Laser. They had the Monitor open the door to the control room and lock the Flood out. However, once inside, Guilty Spark's "protocol" forced him to stop the team from activating Installation 04. He shot Johnson and gravely injured him, locked out the Arbiter from the room, and attempted to kill Master Chief. However, Chief resisted and continued to stand and fight. Just as the Monitor seemed invulnerable, Johnson was able to charge his Spartan Laser and shoot the Monitor, temporarily distracting him. He then told the Chief to "kick his ass" and gave him the Spartan Laser, which Chief used to kill the Monitor for good. In some cases, If the player trades the Spartan Laser with a plasma rifle, then Johnson will appear to shoot himself, though he is alive for the cutscene. Master Chief was determined to save Johnson, but Johnson knew he was going to die.

"If we don't make it-"
"We'll make it."
"It's been an honor serving with you, John."

— Cortana and Master Chief

He gave Chief the chip containing Cortana and told him never to let her go again. His last wishes were to be sent out with a bang. Chief activated Installation 04, as he headed out. Both Cortana and the Arbiter gave their condolences for the loss of Johnson to the Chief. The team fought the Flood as they escaped the Halo. Cortana remembered Johnson had come aboard the Dawn, and told the Chief to use his warthog to escape quickly. After evading death once more, John and the Arbiter made it onto Forward Unto Dawn and escaped the explosion of Installation 04.

The ship then went through the portal, back to Earth.

Distress

"I'll miss you."
"Wake me... when you need me."

— Cortana and Master Chief

Unfortunately for Master Chief and Cortana, the rear half of the ship did not make it back to Earth. The portal wasn't able to sustain itself from the explosion of The Ark and closed as the ship was half way through. Only the front half, with The Arbiter, was able to make it back to Earth while the rear compartment of the ship ended up in the unknown. Cortana, relieved that John survived, explained this to the Chief, and that it could take years before anyone discover their distress signal. Chief, whose armor's life support reserves were slowly draining, then put himself in a cryogenic chamber, to preserve him as the ship traveled aimlessly in space.

Chief's last words before going into cryogenic freeze were "Wake me, when you need me" to Cortana.

Assumed death

Back on Earth, it was assumed that both the Master Chief and Cortana were lost, presumably in The Ark's explosion, since half the ship did not make it to Earth. A memorial was held in Forward Unto Dawn's crash site, for all those lost in the Human-Covenant War. The Chief's Spartan ID number, 117, was carved into the memorial by an unknown person or persons, and taped beside his number was the UNSC Master Chief Petty Officer insignia patch.

Into the Unknown

After an unknown amount of time, the remainder of the Dawn, containing Cortana and the preserved body of the Chief, drifted toward an unknown object, with planetwide city lights that formed the Marathon logo. Master Chief's fate is currently unknown.

Age

Technically, when the events on Halo occurred, he is about 41 years old in "real time". However during the 27 years of war against the Covenant, UNSC ships had to make Slipspace jumps to get from system to system and from battle to battle. It is stated in the official website that "faster-than-light travel is not instantaneous; 'short' jumps routinely take up to two months, and 'long' jumps can last six months or more." It is also known from the novels that UNSC personnel go into deep-sleep in cryochambers during FTL jumps. Therefore, since it is known that the Master Chief and his Spartans were present at dozens of battles in Inner and Outer colonies, the Master Chief's actual biological age should be much younger, as he would have been in cryo-stasis while in transit from system to system and aged almost nothing in the process. This would also explain why Dr Halsey does not seem as old as she should be. Another explanation is that perhaps the human lifespan in that time period is possibly significantly longer and the onset of aging is delayed due to improved medical care in the 26th century, and that the Spartans, including John-117, have been biologically enhanced as well besides the cybernetic augmentation.

John's Face

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A cleaned up version of the video face, notice the pupilless eyes and the scar.

There have been numerous times when people have claimed to see John's face. During the Halo 3 Beta several players posted videos of a possible version of the Master Chief's face. However it was recently revealed that the face seen in the beta was an easter egg inserted into the beta by Bungie, and that it is in fact actually a model of one of the employees.

Prior to this news people disputed the fact that the face was John 117's. First of all, if the armor permutations (for example, the EVA Armor and the CQB Armor) in multiplayer have the face inside the helmet too, it wouldn't be the Chief's (John 117 is still in Mark VI armor in the campaign, and he does not change to any of the armor permutations in the campaign either) Second, it could be there for style. If your camera happens to go through the biped's visor, it wouldn't just go through the biped right away, you would see a face.

117

Main article: 117

The significance of his tag number 117 remains unclear to many fans, though attempts have been made to figure it out. The theories range from biblical, to Marathon, to pure seven references. Inside the Halo Universe the number was simply randomly assigned, but why Bungie chose the number is still being debated.

Quotes

See John-117/Quotes

Trivia

• Master Chief is the first gaming character to become a Madame Tussauds waxwork.
• At the age of six John had brown hair, freckles, and a small gap between his front teeth. It is unknown if he still has those features anymore.
• In Halo 2 Multiplayer or Campaign, if someone presses "down" on the D-pad, the Master Chief biped will put his gun down as if he was ceasing fire. Throwing all your grenades and holding down the left trigger will also produce the same effect. It has been used in many machinima like "Red vs Blue" or "The Codex". Elites can do it too. However, only the latter method works on Xbox Live. This was disabled in Halo 3 but changed to holding down LB,RB,A,crouch,down on the D-pad for 3 seconds your gun should disappear and your player will hold their gun in the cease fire position. If done correctly, you should hear a little noise.
• In both Halo: Uprising Issue 1 and Halo 3, John is referred to as Sierra 117, which is also the first mission name in Halo 3. This refers to the Phonetic Alphabet, as the word for 'S' is Sierra possibly standing for Spartan.
• It is interesting to note that while John is in the navy, in the games he always goes to land when a space battle is happening.
• At the end of Halo 3, shown on the memorial to fallen heroes, the Master Chief Petty Officer insignia next to the 117 carving has three stars, with the third being being covered up by tape. This is the rank insignia for Master Chief Petty Officer of the Navy (highest position for an enlisted soldier). Rank insignia may've changed over the centuries or it may have been a posthomous promotion. It is also interesting to note that this is the good behavior variant of the rank insignia.

Sources

Halo 3 - Believe:"Gravesite" Commercial[1]