Battle of Installation 00

"Our fight is through the Portal, with the Brutes and the bastard Truth!"

- Shipmaster Rtas 'Vadum

The Battle of Installation 00, also known as the Ark Conflict, was a large battle between the UNSC-Fleet of Retribution alliance, the Covenant, the Flood, and Forerunner Sentinels on December 11, 2552. It was the final battle of the Human-Covenant War and was the last stand of the Covenant, making it one of the few major engagements in the entire war in which the Covenant were on the defensive.

Battle of Installation 04
During the Battle of Installation 04, Cortana intercepted the Installation's Index as it was being inserted by Spartan-117. She continued to hold on to it after she had been removed from the Installation's Control Room. She also had spent over twelve hours inside the Control Room's computer, gaining an incredible amount of information about the Halo installations, making her possibly the most knowledgeable regarding the operation of the Halo rings, the Forerunners and the Ark perhaps even more so than 343 Guilty Spark who admitted he was quite ignorant of the Forerunner structures beyond Installation 04.

Battle of Installation 05
The Battle of Installation 05 included many events that would become major factors in the Battle of Installation 00.

The UNSC AI, Cortana, remained aboard the Covenant holy city, High Charity as the Flood and its central consciousness, the Gravemind, took control of it. From there, the Gravemind interrogated her, and she willingly answered its questions.

The aborted activation of Installation 05 had set all of the Halo rings to standby, where they could be activated from the central location of the Ark.

Finally, the Covenant civil war, termed the Great Schism, and the human-Sangheili alliance began in the space around Installation 05.

Battle of Earth
The High Prophet of Truth had arrived on Earth with the rest of his fleet, to complete the digging of a Forerunner structure under the planet surface. Eventually they uncovered and activated it, opening a slipspace portal that would take them to the Ark, a Forerunner structure from which Truth can fire all of the Halo installations at once. As he departed through the Portal, a Flood-captured ship arrived on Earth and crashed. From it, John and the Arbiter were able to extract a message from Cortana, alerting them that High Charity was heading for Earth and indicating that the solution to the problem of the Flood lay beyond the portal.

While Lord Hood was suspicious of Cortana's warning and objected to going through the portal, Commander Miranda Keyes, Spartan-117 and Ship Master Rtas 'Vadum all indicated their wish to proceed through the Portal. Lord Hood gave Miranda Keyes command of the Forward Unto Dawn for the human commitment to the mission and the fleet of ships chased after the High Prophet of Truth.

Battle
"Sangheili Major"

- Rtas 'Vadum

The Fleet of Retribution exited slipspace in the vicinity of the Ark on December 11, 2552, where they found the Prophet of Truth's fleet waiting for them. Despite being outnumbered three-to-one, Rtas 'Vadum declared that they were fairly matched and the Sangheili promptly engaged the enemy fleet while the Forward Unto Dawn deployed six D77H-TCI Pelicans to locate Truth. Truth presumably landed the Forerunner Dreadnought on the Ark. It was never seen again and did not to take part in the battle above the Ark.



Operation: BLIND FAITH
Despite being harassed by Covenant Seraph fighters, five of the Pelicans deployed by the Forward Unto Dawn managed to made it to the Ark's surface. Two of the Pelicans traveled to a vast desert, where they deployed the Master Chief and four ODSTs onto a cliff edge. The team made it to a ledge overlooking a group of Jiralhanae, Unggoy, and Kig-Yar listening to a message from Truth. Waiting for the Spartan to take the first shot with his sniper rifle, the team proceeded to engage the clustered Covenant force. As their numbers dwindled, more Jiralhanae and several Carbine-wielding Kig-Yar arrived to reinforce the Covenant but ultimately the humans were successful in eliminating the Covenant soldiers. The team than proceeded through another cave which emerged into a larger area where Covenant forces were assembling an Anti-Aircraft Cannon. Recognizing the grave threat that the gun would be to the Forward Unto Dawn, the team promptly attacked the Covenant, forcing the Phantom that was carrying components of the Anti-Aircraft Cannon to drop them and flee. As the team started to get an upper hand on the Covenant forces, another Phantom arrived on the battlefield, dropping a Mgalekgolo pair to engage the humans while the rest of the Covenant fell back to regroup. Despite the opposition, John-117 and the ODSTs managed to defeat the Mgalekgolo pair, before rooting out the surviving Covenant soldiers on the nearby rise. A final Jiralhanae Captain and a large group of Unggoy met the humans as they ascended the rocky pathway but they too failed to stop the team.

The team then entered a small cave, where the Chief first accessed the Forerunner Terminal network. On the other side of the cave they met a pair of Marine survivors from a nearby shot down Pelican and witnessed a GA-TL1 Longsword fighter crashing. After being informed of a possible landing zone for the Forward Unto Dawn, the humans ambushed the Jiralhanae and Unggoy searching the crashed Pelican. A pair of Jiralhanae Prowlers then entered the area, with one stopping to disgorge its occupants while the other one remained on the move, using its plasma cannon to strafe the humans. After a struggle, the team managed to kill all of the hostiles in the area. Finding that several Mongooses had survived the Pelican crash, the humans mounted up on the vehicles. They then entered a much larger open area where the Longsword had crashed. A large Covenant force including Ghosts and Choppers occupied the area but the now-mobilized UNSC party was successful in wiping them out. Passing the crashed Longsword and a pair of SOEIVs that had landed and had the ODSTs which had once occupied them killed once they left their pods, the team arrived at a crashed Phantom, where they promptly wiped out its surviving passengers. The team than located a large Forerunner wall where a group of Covenant were being engaged by the Sentinel defenders. With the assistance from the Sentinels, all of the Covenant were eliminated. Avery Johnson descended in his Pelican, informing the Master Chief that he had spotted a structure that was similar to the Cartographer of Installation 04 on the other side of the wall, and Keyes set it as their objective. The Dawn would need to land first however, in order to deploy a vehicular force that would be sufficient to punch through the Covenant forces in front of the Cartographer building. With the Sentinels providing aerial support, the team proceeded forward, destroying a pair of Ghosts before assisting a group of Marines being attacked by more Covenant. The vehicles led by the Chief then moved to the sighted Landing Zone, which was occupied by Ghosts, a Wraith, several deployable lookout towers and a pair of Anti-Air Wraiths that were firing into an aerial battle between Banshees and Hornets. Despite staunch opposition, the human force was able to clear the landing zone, allowing the Dawn to disengage from the space battle and descend to the surface of the installation, landing safely.



From the Dawn's hangar, the Master Chief was reinforced with three Scorpion tanks, a Warthog and more Marines. A Pelican arrived to transport the surviving ODSTs away while the rest of the soldiers mounted up. With 343 Guilty Spark having arrived to guide them, the mechanized force then fought their way back to the Forerunner wall, destroying untold numbers of Covenant vehicles and ground troops. Arriving at the wall, which the Covenant had now reinforced with a number of Wraiths, the UNSC troops were forced to clear out all of the defenders in order to make it to the wall. The Chief, along with Guilty Spark, went through the upper, smaller doorway while the rest of the UNSC force, now reinforced with two more Warthog's, one of which was a Gauss Warthog, went through the larger, lower doorway. The Spartan arrived at a platform overlooking a deep chasm. Here, the Monitor guided John-117 to activate the light bridge that would allow the rest of the force to move onward. The Chief continued through the wall, emerging outside as a Scarab passed over him. Far below, a Covenant armored force destroyed the Warthogs that had emerged from the wall first. The Gauss Warthog, harassed by Ghosts and losing its gunner, made its way up to the Chief, where the driver offered the vehicle to the Spartan. The Chief made his way down a winding path, his gunner destroying the Ghosts and a plasma cannon before regrouping with the force of Scorpion tanks. Sergeant Stacker and the Chief led the Scorpions against a battalion-sized force of Covenant heavy armor, including Choppers, Ghosts, Wraiths and infantry with heavy weapons, reinforced by a Phantom. The Scarab than returned to the area, but even with its presence, the humans were able to clear out all of the Covenant, with John-117 personally taking down the Scarab. As the Scarab went down, Rtas 'Vadum announced that his fleet had wiped out all of the Prophet of Truth's ships; despite being outnumbered three-to-one in space, the Sangheili fleet made short work of the Covenant space forces due to the Jiralhanae being outmatched by the Sangheili in their knowledge of naval warfare, and the Shadow of Intent landed near the Cartographer.

The Chief and his forces dismounted from their vehicles, fighting their way up a series of ramps towards the entrance to the to the Cartographer building. At the top, they met with Thel 'Vadam, who dismounted from a Pelican along with a pair of Marines to accompany the Chief inside. With the help of 343 Guilty Spark, who unlocked several locked doors, the team entered a room where a number of Unggoy were sleeping. The Arbiter advised the Chief to kill them while they slept. Killing all of the Unggoy and their Jiralhanae overseer, the team continued downward, eliminating more unaware Covenant in another room before a Jiralhanae soldier gave away their position in yet another room. Despite their presence now being know, the team were able to fight through to an exterior platform where the Cartographer terminal itself was. The Chief accessed the terminal, learning that Truth had already fortified himself in a facility that would allow him to remotely activate the entire Halo Array in the core of the Ark and had activated a large barrier around the entire core to ward off the attacking forces. After discovering Truth's location, a Phantom swooped in to attack. Thel 'Vadam drew its fire, allowing the Chief to escort Spark clear. Johnson announced that there was a large force of Covenant aerial support heading towards their location, and led the air battle against them while 'Vadam stole a Banshee to assist him. The Chief met with one of the Marines, who informed him that the Pelicans would land a level down from their current position. Shortly after, a group of Unggoy threw plasma grenades that killed the other Marine who was guarding the entrance to the room. The Chief and the Marine killed the Unggoy as well as a War Chieftain and his Bodyguards. They then moved downward, emerging onto the upper level of a seemingly-empty room aside from one occupant; Jiralhanae Chieftain Cethegus. The Chieftain took a moment to taunt the Spartan, before leaving the room for the exterior platform. A group of camouflaged Jiralhanae Stalkers then attacked the Chief.

Outside, Cethegus regrouped with the Jumpers from his pack, and was addressed by a hologram of the Prophet of Truth nearby. Cethegus was to defeat the Spartan in single combat, his failure to do so bringing him a fate worse than death. By this point, John-117 had slain the Stalkers and made his way out on to the platform. The Jiralhanae Jumpers moved back, allowing Cethegus to challenge the human. The ambitious Chieftain charged at John-117. After a struggle, the Master Chief was able to best Cethegus. As the Chieftain fell, the rest of his pack sprung into action, hoping to avenge their fallen commander, but they were unsuccessful and the Spartan was soon the sole survivor of the encounter. Pelican Kilo 023 arrived to pick the Spartan up. After some initial uncertainty regarding a huge flock of Sentinels that were heading elsewhere on the installation, the human-Sangheili alliance decided that until the Prophet of Truth was stopped, nothing else mattered, and they left the Cartographer.

Battle of the Citadel


The UNSC assault team, travelling in five Pelican dropships, along with a pair of Sangheili Phantoms began their attack on a trio of towers that, once disabled, would drop a section of the barrier protecting the Citadel in which the Prophet of Truth was located. As the assault force closed in, they split up. Two Pelicans, including Kilo 023 containing the Master Chief and a squad of ODSTs would hit the first tower. The Phantoms, which carried Thel 'Vadam and his Sangheili, would assault the second and the other Pelicans, ferrying Sergeant Johnson and his squad would disable the third tower. As Kilo-023 and her wingman approached the first tower, they started to take fire from an Anti-Aircraft Wraith stationed on a beachhead near the tower. Kilo-023's wingman was struck in her right wing by AA fire, which rocketed her forward into Kilo-023, crushing the Warthog that was slung underneath before she spiraled into the ground. Kilo-23 was able to continue forward and landed on the beach nearby. John-117, carrying a Spartan Laser, lead the ODSTs against a large Covenant force that was protecting the AA Wraith. Fighting their way past the crashed Pelican, the team was able to take down a War Chieftain and his entourage before the Master Chief neutralized the Wraith. With the beachhead secure, Commander Keyes arrived in her Pelican to deliver a Warthog and Mongoose for the team to use in their assault on the tower. At the same time, the Shadow of Intent began a diversionary bombardment against the barrier, firing plasma torpedoes at the barrier shield.

The team soon arrived at the entrance to the first tower, finding it heavily defended with a Wraith, a pair of Prowler, numerous Ghosts, Shade turrets and other infantry. As the battle around the tower raged, Keyes' Pelican returned to drop ordnance pods containing weapons for the team. Eventually clearing the area, the team proceeded inside, where they fought through more Covenant forces. Making their way to the elevator that would lead to the tower controls, John-117 went alone while the rest of the team waited behind to watch for hostiles. Before he could deactivate the tower however, the Spartan had to contend with a Jiralhanae pack lead by a Chieftain. Eventually clearing the room, John-117 located the controls and shut the tower down. At the same time, Thel 'Vadam and his Sangheili disabled theirs. Unfortunately, Sergeant Johnson and his team ran into heavy resistance at the third tower. Johnson managed to make a final transmission warning Keyes to keep her Pelican clear because of the number of hostiles before he was cut off. Commander Keyes then ordered the Chief to meet up with Thel 'Vadam and jointly assault the third tower. The Chief returned down to the lower level, where he helped his team fight off a small group of Covenant trying to reactivate the tower. They then returned to their vehicles and made their way back to the beachhead. There, a UNSC pilot offered his Hornet to the Chief. The Spartan, with the aid of several other Hornets and Pelicans, made their way to the airspace around the second tower where the Sangheili Phantoms were under heavy attack from a large number of Banshees and a Covenant Phantom. The UNSC air force promptly engaged the Covenant, allowing the Sangheili to engage their Phantom's cloaking systems to escape. The UNSC were able to clear the vicinity of the second tower before making their way onward to the third. The third tower was heavily defended by a pair of AA Wraiths, Shades, another standard Wraith and a huge group of Jiralhanae lead by a fuel rod gun-wielding War Chieftain. The Chief managed to knock out the anti-air, allowing the Sangheili Phantoms to return, where they disgorged Thel 'Vadam and his men to begin a ground-side push. Ultimately, the combined assault from the air and the ground managed to collapse the Covenant defenses.



Landing his Hornet, the Chief, along with Thel 'Vadam and a unit of Sangheili made their way into the tower, engaging the surviving Jiralhanae from the battle outside the tower. Here they discovered the corpses of several of the Marines from Johnson's group, but the Sergeant himself wasn't among them. Inside the tower, the team was confronted by a Mgalekgolo pair and a massive swarm of Yanme'e who descended from above. After a protracted battle, the team was able to wipe out the Mgalekgolo and most of the Yanme'e, the survivors retreating from the way they came. As they made their way up to the elevator, another pack of Jiralhanae as well as the surviving Yanme'e vainly tried to halt their progress but failed. Once more, the Chief proceeded to the tower controls by himself, wiping out a group of Stalkers and their War Chieftain commander. Once the Spartan activated the controls, the barrier dissipated immediately. The Shadow of Intent prepared to bombard the Citadel, but was prevented from doing so when the Flood-infested High Charity arrived, launched debris that crippled the Sangheili carrier and spread Flood across the Ark. Keyes insisted that this would only pressure Truth into activating the rings, and ordered her remaining forces to attack him directly.

One of the pieces of debris from High Charity crashed through the window of the room John-117 was in. In moments, the Spartan was swarmed by Flood forms, with Pod infectors reanimating the fallen Jiralhanae into combat forms. Fighting through the Flood, the Chief returned to the lower level where he found 'Vadam and his Sangheili engaging more Flood. Pushing through numerous Flood forces, the team made it outside where Pelicans were in the process of deploying armored vehicles for the push towards the Citadel. John-117 and Sergeant Stacker lead the assault force, which included a Scorpion tank, a Gauss Warthog and a Mongoose. The assault force fought through the cliffs to the cliffside near the Citadel. Here, the Jiralhanae threw everything they had at them - Wraiths, Ghosts, Prowlers, Shade turrets and heavy weapon-wielding infantry attempted to counter the UNSC armored vehicles while Banshees and Phantoms fought against Hornets and Pelicans for superiority in the air. After a tough battle, the UNSC ground forces pushed through to a break in the cliffs that would allow them to make their way to the entrance to the Citadel. Sergeant Stacker called in more Hornets to land nearby for the Chief to use as a pair of Scarabs arrived in front of the Citadel as the Covenant's last line of defense. After a lengthy battle, John-117 was able to take out one of the Scarab walkers. At this point, Commander Keyes ordered all forces to focus their fire on the second Scarab. Under the sustained assault, it didn't take long for the Scarab to buckle, before John-117 finished it off. With the Scarabs down, any remaining Covenant stragglers were soon moped up by the UNSC.

A Phantom dropped Thel 'Vadam and 343 Guilty Spark in front of the Citadel, where they met up with John-117. Spark activated a light bridge and the Spartan and Sangheili entered the Citadel alone. As they made their way in, several viewscreens light up showing the Prophet of Truth giving a speech attempting to reassure his remaining followers to hold firm and also declaring that he was about the activate the Halo Array. Realizing that they had very little time left, Spartan-117 and Thel 'Vadam hastily made their way to the elevator that would carry them to Truth's level.

Sergeant Major Johnson, who had disappeared during the assault on the barrier towers, had in fact been captured by Truth's forces and was being tortured into pressing the switch to activate the Array; Truth needed a "Reclaimer" to perform the action. Johnson attempted to goad the Chieftain that was holding him into killing him to prevent this, but Truth realized this and stopped him. With Spartan-117 and the Arbiter too far away to stop the Prophet, Commander Keyes took her Pelican dropship and crashed it directly into the facility in an attempt to rescue Johnson. She attempted to hold off Truth's Jiralhanae Bodyguards with a shotgun and a magnum, but it became apparent that she wouldn't be able to kill all of them, and Truth taunted that either her or Johnson would activate the Array. Realizing what needed to be done, she pointed her pistol at Johnson, who encouraged her to shoot him and then herself to deny Truth a means to activate the rings. Before she could however, Truth used a Spiker to shoot Keyes in the back, killing her. Johnson, completely stuck by grief and shock, is easily made to press the panel, starting the activation sequence for the Halo Array. At this time, John-117 and Thel 'Vadam arrived on that level, where they were confronted by a pair of Flood tank forms. Instead of attacking, the Gravemind spoke to the pair through the Flood forms, offering an alliance to stop their common foe, knowing that only the Chief would be able to stop the activation sequence. Unable to see another way, the two agreed and they began a combined assault on the last bastion of Covenant soldiers protecting the Prophet of Truth.

A large group of Unggoy and Kig-Yar lead by a Jiralhanae Captain guarded the first bridge. The two tank forms lumbered into their midst, the huge Flood forms easily crushing the smaller Covenant soldiers. With large numbers of Pod infectors along with the efforts of the Spartan and Sangheili, the forces on the first bridge soon crumbled. On the second bridge, a pack of Jiralhanae including a unit of Jumpers fought viciously to halt the process of John-117, Vadam and the Flood, but with each Jiralhanae that fell, a new Flood combat form was produced and as a result, the Covenant forces began to collapse. Even the Chieftain and a group of fuel rod gun-wielding Unggoy Heavies failed to stop the determined assault. The Covenant defenders on the third and final bridge were slaughtered by the Flood before the Chief and Thel even arrived. With that, all Covenant in the Citadel had been eliminated, and the way to Truth was clear. Crossing the light bridge to the Citadel controls, the Chief and 'Vadam passed by several Flood corpses and found Johnson cradling the dead body of Commander Miranda Keyes. He urged John-117 to stop the rings. Thel 'Vadam approached Truth, who was on the floor and had already been partially infected by the Flood. Declaring his intent to have his revenge against the Prophet as the infection began to ravage Truth's body, 'Vadam allowed the Prophet to live long enough to see the Chief deactivate the Halo Array. In a final defiant declaration, Truth announced himself as the voice of the Covenant, before being fatally stabbed in the back by Thel's energy sword. With Truth's death, the Covenant was brought to an end.



Almost immediately after the death of the Prophet of Truth, the Gravemind announced his sudden betrayal, his tentacles surrounding the platform. Johnson attempted to airlift John-117 and Thel away but one of the Gravemind's tentacles struck the Pelican, sending it spiraling out of control and knocking the pair to the ground near the platform. The two quickly got to their feet, standing back to back with their weapons ready as the Gravemind taunted them. Thel acknowledged that they had traded one villain for another. Suddenly, the Gravemind retracted his tentacles below the platform as a pair of combat forms clambered up to challenge the pair. Quickly slaying the combat forms, the Master Chief and Arbiter hastily made their way back towards the lift they had used to enter at Johnson's urging. As they went, myriad Flood forms attempted to stop their progress. On the second bridge, a squadron of Sentinels arrived to assist the duo. With the assistance of the Forerunner constructs, John-117 and Thel soon made their way back to the lift. Discovering that the controls aren't working, they opt to use a shaft at the back of the lift. The Spartan enters first. A flickering image of Cortana leads him to a control panel. Upon activating it, an incomplete Halo ring rose out of the Ark's Foundry; it was suddenly clear what Cortana's "solution" to the Flood was. Realizing what needed to be done, John-117 announced his plan to fire the ring to 343 Guilty Spark. The Monitor agreed that a tactical pulse would eradicate the local Flood infestation and made his way to the ring for final preparations. The incomplete ring lacked an Activation Index however. The only way they could get another Index was to rescue Cortana from High Charity since she still possessed the Index from Installation 04.

Johnson picked up the Arbiter and the Chief while Guilty Spark went off to the new Installation. The party then headed to the Shadow of Intent, where Johnson, 'Vadam, and Ship Master 'Vadum rounded up the UNSC and Sangheili forces. Meanwhile, Master Chief infiltrated High Charity, successfully recovering Cortana and the Index and sabotaging the city's reactors. He escaped with the help of 'Vadam and fled onboard a crashed Pelican as the station exploded, ostensibly destroying the Gravemind.

Finishing the fight
"Rtas 'Vadum"

- Thel 'Vadam

With the Index secure, Thel 'Vadam ordered Rtas 'Vadum (who had safely evacuated humans and Sangheili back onboard the Shadow of Intent) to escape back through the slipspace portal to Earth while he, Spartan-117, and Sergeant Major Johnson moved in on the Control Room of the incomplete Halo. The Dawn was left behind for them to use to escape. The Gravemind, meanwhile, had begun to rebuild itself on the new ring, and sent Flood dispersal pods to kill the three interlopers. The Chief, 'Vadum, and Johnson, with the assistance of local Sentinels and 343 Guilty Spark, fought through the Flood and entered the Control Room. Spark explained that the new Halo would be ready to fire within days, to which the group, particularly Johnson, protested. When Guilty Spark informed the three that activating Halo now would destroy both the Ark and the installation, Johnson told him to "deal with it" and prepared to activate the ring.

"Send me out...with a bang."

- Johnson's last words

Unwilling to let "his" ring be destroyed again, 343 Guilty Spark went rampant, mortally wounded Johnson, took down Spartan-117's shields and blew the Arbiter out of the room. However, with the help of a dying Sergeant Johnson and his Spartan Laser, Spartan-117 managed to destroy Guilty Spark and start the firing sequence of the new Halo. He and the Arbiter then took Johnson's Warthog and rushed towards the Dawn as the incomplete Halo powered up and started breaking apart. The two drove their way through hordes of battling Flood and Sentinel drones, with the ring world literally falling to pieces around them. The two heroes made it onto the Dawn, where the Arbiter was almost crushed by a Scorpion Tank due to the sudden acceleration of the ship. Agility and a pair of crates saved him. Spartan-117 then inserted Cortana into a holotank and she activated the Dawn's engines. The Arbiter made his way to the bridge of the ship and took her into Slipspace just as the new Halo fired, with Master Chief almost being crushed by the same tank which descended through the cargo hold and into space. However, the Slipspace portal collapsed as the Dawn entered it, and while the forward half with the Arbiter made it to Earth, the rear half fell out of Slipspace at an unknown location, with Cortana and Spartan-117 floating into the dark abyss.

The Battle of Installation 00 ended the Human-Covenant War. Months later, a monument was erected near the remains of Voi in remembrance of those who died in the line of duty, including Spartan-117 who was labeled MIA. The Arbiter, the Shipmaster and their brethren then departed Earth for Sanghelios.

Aftermath
"For us, the storm has passed. The war is over. But let us never forget those who journeyed into the howling dark, and did not return. For their decision required courage beyond measure; sacrifice, and unshakable conviction that their fight, our fight, was elsewhere. As we start to rebuild, this hillside will remain barren. A memorial to heroes fallen. They ennobled all of us, and they shall not be forgotten."

- Fleet Admiral Terrence Hood in the memorial ceremony

Installation 00 and the Flood
The firing of the Halo ring caused unprecedented damage to the Ark while sterilizing the installation of the Flood forces around and on it, including the Gravemind commanding the massing Flood amid the battle. Over two years later on March 20, 2555, during Operation: FAR STORM, Luther Mann and N'tho 'Sraom arrived at the Citadel to stop the Halos from firing. Scattered around the basin were the remains of human and Covenant vehicles left over from the battle, including the empty husks of the two Scarabs.

Forward Unto Dawn
The Portal between Installation 00 and Earth collapsed while was still inside it. As a result, the ship was cut in half; the front arriving at Earth and the back half being lost in space. The Arbiter, sitting on the bridge at the time, was part of the front half but, without any engines, soon crashed into the ocean. However, John-117 and Cortana were in the rear half and were declared MIA by the UNSC. In reality, they had survived the Portal's collapse. John-117 went into cryo-sleep while Cortana activated an emergency locator beacon indicating their status. After drifting in an unknown region of space for over 4 years, the rear half of the Dawn was caught in the gravity well of a Forerunner shield world known as Requiem.

Legacy
"Jerome-092"

A monument was made near the town of Voi, not far from the portal structure. It read, "In memory of those fallen in the defense of Earth and her Colonies. March 3, 2553." On it were photos of UNSC personnel who went through the portal but did not return; John-117 was honored with an etching of the number "117" and an erroneous Master Chief Petty Officer of the Navy badge taped next to the number. With the exception of Thel 'Vadam, the Sangheili were not present at the dedication service, instead remaining aboard Shadow of Intent. After the ceremony, Lord Hood, despite being unable to forgive the Sangheili for what they did to humanity at the beginning of the war, shook 'Vadam's hand and thanked him for standing beside the Master Chief at the Ark. The Arbiter then departed to Shadow of Intent, and joined Rtas 'Vadum on the bridge, both agreeing to return to Sanghelios to ensure its safety. Thel 'Vadam was given command of the carrier and all Sangheili onboard departed for their homeworld.

In March 2555, the Ark's monitor, 000 Tragic Solitude, sought revenge against humanity for damaging the Ark years prior. To do so, the ancilla placed the remaining Halos on a brief countdown to activation, prompting a joint UNSC-Swords of Sanghelios mission to the installation to stop the rings from firing. After Solitude's plan was thwarted, the UNSC established research facilities on the Ark.

The Banished arrived on the Ark in November 2558, killing UNSC personnel across the installation. In March 2559, the crew of the newly arrived engaged the Banished with help from Isabel, the logistics AI of one of the UNSC research facilities. Approximately six months after the initial hostilities with Spirit of Fire, a force of Banished warriors lead by Voridus used a Scarab to blast a hole in the containment shield around the ruins and rubble of High Charity, as they sought to scavenge materials to aid their ongoing struggle against the UNSC. This inadvertently caused a Flood outbreak onto the installation, leading to a desperate struggle between the Banished and the parasite. After some time, the Banished managed to destroy a Proto-Gravemind that was moments away from becoming a Gravemind and the Ark's Sentinels once again quarantined the Flood.

Ships
UNSC

Sangheili
 * Shadow of Intent
 * Pious Inquisitor

Covenant
 * Twilight Compunction
 * Gathering of Praise

Units
UNSC
 * UNSC Home Fleet
 * 105th ODST Division
 * 7th Shock Troops Battalion
 * 11th Marine Force Reconnaissance/ODST
 * S4/BLCE/1/7
 * S4/BRT/1/7
 * Alpha Company
 * Charlie Company

Allied Sangheili
 * Fleet of Retribution

Covenant
 * Truth's fleet

Personnel
UNSC
 * Commander Miranda Keyes
 * Master Chief Petty Officer John-117
 * Cortana
 * Lieutenant Hocus
 * Sergeant Major Avery Junior Johnson
 * Gunnery Sergeant Reynolds
 * Gunnery Sergeant Stacker
 * Private First Class Chips Dubbo

Fleet of Retribution
 * N'tho 'Sraom
 * Shipmaster Rtas 'Vadum
 * Arbiter Thel 'Vadam
 * Usze 'Taham

Covenant
 * Prophet of Truth
 * Cethegus
 * Hekabe and his family clan

Forerunner
 * 343 Guilty Spark
 * Mendicant Bias
 * 000 Tragic Solitude

Flood
 * Gravemind

List of appearances

 * Halo: First Strike
 * Petra
 * Halo 3
 * Halo Legends
 * Origins
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * From the Office of Dr. William Arthur Iqbal
 * Halo: Broken Circle
 * Halo: Hunters in the Dark
 * Halo Mythos
 * Halo: Tales from Slipspace
 * Dominion Splinter
 * Halo Wars 2
 * Halo: Envoy
 * Halo: Legacy of Onyx
 * Halo: Bad Blood