Battle of Installation 00

The Battle of Installation 00 was a large battle between the UNSC-Covenant Separatist alliance, the Covenant Loyalists, the Flood, and Forerunner Sentinels. It was the final battle of the Human-Covenant War and the Covenant Civil War. The Battle of the Ark and the last stand of the Covenant marked one of the few major engagements in the entire war that 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 and the Human-Separatist alliance began in the space around Installation 05.

Second Battle of Earth
The High Prophet of Truth had arrived on Earth and began digging for a Forerunner structure. Eventually they uncovered and activated it, opening a 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, they 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
The High Prophet of Truth, having successfully activated the artifact in Voi, left Earth through a Slipspace portal to the Ark, a Forerunner structure that can be used to fire all of the Halo installations at once. Despite Lord Hood's urging, Commander Keyes took the Forward Unto Dawn with a small fleet of Separatist Cruisers led by the Assault Carrier Shadow of Intent and proceeded through the Slipspace portal, arriving at the Ark. The Separatists immediately engaged the Brute fleet stationed to protect the Prophet while the Dawn and the Aegis Fate deployed the Master Chief and Orbital Drop Shock Troopers in six Pelicans to locate Truth. Despite being outnumbered three-to-one in space, the Separatist fleet made short work of the Loyalist space forces, likely due to the Elites remarkable tactical adeptness. The Brute's tactical haplessness can be heard in a radio transmission, saying "No! Shoot the Carrier!" The Covenant Loyalist Fleet had been destroyed and the only Loyalists left alive were Truth and his forces on the Ark. Also, presumably Truth landed the Forerunner Dreadnought on the Ark although it was never seen again and was specifically said not to take part in the battle above the Ark.



Five of the Pelicans deployed by the human Frigates had made it to the Ark. The Master Chief and four ODSTs were deployed, ambushing a group of Brutes, Grunts, and Jackals listening to a message from Truth. They then proceeded to ambush another group of Covenant Loyalists building an Anti-Aircraft Gun. They 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 second shot down Pelican and witnessed a Longsword fighter crashing. After being informed of a possible landing zone for the Forward Unto Dawn, the humans ambushed the Brutes and Grunts searching the crashed Pelican, then destroyed a pair of Brute Prowlers that attacked. Now with Mongooses and Prowlers, they continued past the crashed Longsword, a pair of HEVs that had landed and had the ODST's which had once occupied them killed once they left their pods, and a crashed Phantom to a battle between Covenant and Sentinels outside a Forerunner barrier. Avery J. Johnson informed 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. After meeting another group of Marines being attacked, the vehicles led by the Chief then moved to the sighted Landing Zone, which was occupied by a pair of Anti-Air Wraiths. After they cleared the LZ, the Dawn disengaged from the space battle and dived onto the surface of the installation, landing safely.



From the Dawn's hangar, the Master Chief, ODSTs, and Marines were reinforced with three Scorpion tanks and a Warthog. The human force then fought their way through a large reinforcements force back to the Forerunner wall. The Chief went through the upper, smaller doorway while the armor and vehicles (reinforced with one more Warthog and a Gauss Warthog) went through the larger, lower doorway. After activating a light bridge the Spartan went through the wall, only to see a Scarab and a Loyalist armored force destroy the Warthogs. He then fought his way to the lower doorway, which then finally opened fully, letting the tanks through. Sergeant Pete Stacker and the Chief led the Scorpions and a Warthog through two Loyalist defense lines of Choppers, Ghosts, Wraiths, and infantry with heavy weapons, reinforced by a Phantom. When the Scarab returned, the humans then proceeded to destroy it, plus the Choppers and infantry reinforcing it. By now the Elites had defeated the entire Loyalist space fleet. The Shadow of Intent, landed near the Cartographer. The Aegis Fate had landed on a Brute-controlled desert Forerunner facility and demolished the forces there. Rtas 'Vadum likely ordered all his remaining ships except for the Shadow of Intent to go back to Earth and wait for his return.



343 Guilty Spark, now working with the UNSC-Separatist alliance, led Spartan-117 and the Arbiter Thel 'Vadam, plus a pair of Marines, to the Ark's Cartographer. Fighting their way through several incompetent forces that were asleep, they get back outside where they pinpoint the Prophet's location. By then Truth had already holed himself in a secure facility in the core of the Ark and had activated a large barrier around the entire core to ward off the attacking forces. After discovering Truths location, the UNSC-Separatist troops were attacked by a large Loyalist air force. Johnson led the air battle against them, and 'Vadam stole a Banshee to help him. The Chief, with the pair of Marines, fought his way past a Brute Chieftain and his squad and a group of Stalker Brutes. He then dueled with a Brute Chieftain and defeated squad of Jump Pack Brutes before being picked up by Pelican Kilo 23 after the Loyalist air force was dealt with. The humans and Elites set forth to attack Truth to stop him from activating the rings.

Battle of the Citadel


The UNSC ground forces, carried in five Pelicans, along with Separatist reinforcements in a pair of green Phantoms, assaulted three emitter pylons that powered a small section of the barrier. The Master Chief and a pair of ODSTs were deployed a distance from the first tower by a Pelican after hostile fire shot down a second Pelican carrying Marines and a Warthog. The crashing Pelican also took out the ODST's Warthog. Thel 'Vadam and Elites assaulted the second tower. Sergeant Johnson took four Marines and attacked the final tower. Clearing the Loyalists heavy weapons on the beach, a new Warthog and a Mongoose were deployed and taken through heavy resistance to the tower. Clearing it, the Chief learned that the Separatists had taken down the second tower, but Johnson had been ambushed by enemy reinforcements. The Chief returned to the beach, commandeered a Hornet and helped destroy Loyalist Banshees and a Phantom, securing air control for the UNSC-Separatist forces outside the barrier. Destroying the Brute defenders outside the third tower with Hornets and Pelicans, Master Chief, Thel 'Vadam, and a team of five Elites discovered the corpses of the Marine team, except for Johnson's. When the defending forces were eliminated and the barrier deactivated, the Shadow of Intent began its attack on Truth. At the same time the former Covenant city ship High Charity arrived from Slipspace and crashed on the Ark. Debris spread from the city ship heavily damaged the Shadow of Intent and helped spread a new Flood infestation on the Ark as a means to stop Truth and to be safe from the Halo activation array. Keyes insisted that this would only pressure Truth into activating the rings, and ordered the remaining forces to attack him directly.

Fighting through an infestation of the Brutes they had just killed and Johnson's Marines, the Elites and the Chief met up with Sergeant Stacker's Marines, supported by a Scorpion, a Gauss Warthog, and a Mongoose. The humans and Elites fought through the cliffs into the Citadel where the Halos could be activated was located. The Loyalists attempted to reinforce their troops by a large amount of Phantom transports gathered from around the installation, but the UNSC air forces countered this by attacking the Phantoms and their Banshee escorts with Hornets and Pelican Gunships. The ground forces managed to destroy the remaining Loyalist armor on the mountainside. Given another Gauss Warthog and air support from a flight of Hornets and a Pelican, the Marines destroyed Banshees, Ghosts, a Prowler, plus a pair of Scarabs dropped in front of the Citadel by Brutes. After the destruction of the Scarabs, the Loyalists had lost their grip on the Citadel area. Without any heavy support, Spartan-117 and 'Vadam personally attacked the facility where Truth was to activate the Halo installations.

Sergeant Major Johnson, who had disappeared during the assault, was in fact captured by Truth's forces and was being tortured into pressing the final switch to activate the other Halos. Commander Miranda Keyes was killed by the High Prophet of Truth with a Spiker. With Spartan-117 and the Arbiter too far away to stop High Prophet of Truth, Commander Keyes grabbed a Pelican dropship and crashed into the facility to rescue Johnson, but was killed soon after by Truth himself. However, her actions delayed Truth long enough for Spartan-117 and the Arbiter to stop him. The Gravemind dispatched Flood forces to assist Spartan-117 and the Arbiter in preventing the Halos' activation and the Arbiter personally killed Truth. However, the Gravemind betrayed them and while Johnson managed to escape with Commander Keyes' body in the Pelican, Spartan-117 and the Arbiter had to fight their way outside. 343 Guilty Spark had managed to facilitate the making of a new Halo through the Ark, explaining that a tactical pulse from it would eliminate the Flood infestation. However, this new Halo lacked an Activation Index. 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 Sanghelli forces. Meanwhile, Master Chief (and the Arbiter in Halo 3 Co-op) headed towards High Charity via Banshee. Through a tough battle, Spartan-117 and the Arbiter successfully entered the ruins of High Charity and recovered Cortana, using a partly-damaged Pelican to escape while High Charity was destroyed as its reactors went critical after the they blasted them.

Finishing the Fight
With the Index secure, Thel 'Vadam ordered Rtas 'Vadum (who has 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. By now what was left of the Gravemind had relocated to the new Halo. The three heroes with 343 Guilty Spark made it through waves of Flood to the Control Room. 343 Guilty 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.

Unwilling to let "his" ring be destroyed again, 343 Guilty Spark went rampant, mortally wounding Johnson and attacking Spartan-117 and the Arbiter. 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 world literally falling to pieces around them. The two heroes made it to 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. He made his way to the bridge of Dawn 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 with Cortana and Spartan-117 floating into the dark abyss.

With Truth dead, the Halos deactivated, and the Flood destroyed, the Battle of the Ark ended the Human-Covenant War. A monument was erected in New Mombasa in remembrance of those who gave their lives in the war including Spartan-117 who is labeled MIA. The Arbiter and his brethren then departed Earth for Sanghelios.

Aftermath
"Send me out, with a bang."

- Johnson's last words

Installation 00 and the Flood
It is assumed that the firing of the Halo ring either severely damaged or destroyed the Ark while killing the Flood forces around Installation 00, including the Gravemind commanding the massing Flood amid the battle.

Forward Unto Dawn
The Portal between Installation 00 and Earth collapsed while Forward Unto Dawn 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. However, Spartan-117 and Cortana were in the rear half and were missing.

It is known that Cortana and Spartan-117 survived the Portal's collapse. Spartan-117 went into a cryogenic-tube while Cortana sent out a signal indicating their status. It is unknown if their message was ever received or if they were rescued. The amount of time that passed in the interim is unknown, and it is also unknown if Cortana succumbed to AI Rampancy or even survived the course of the journey, as UNSC Smart AI minds become too interlinked and "think themselves to death" after approximately seven years of operational service. If you complete the campaign on legendary, there is a last cutscene that shows Master Chief and Cortana near an unknown planet.

Legacy
A monument was made near the town of Voi where the Forerunner artifact had been built. It reads "In memory of those fallen in the defense of Earth and her Colonies. March 3, 2553." On it were the pictures of the most outstanding UNSC personnel who went through the Portal but did not return. Spartan-117 is honored on it by a "117" scratched onto the monument and a Master Chief Petty Officer of the Navy badge taped on the monument.

The Sangheili overlooked the Hillside Memorial, with Thel 'Vadam being the only to attend due to fighting alongside SPARTAN-117. After the ceremony, he and Lord Hood, who still can't forgive the Sangheili for what they did to Humanity at the beginning of the war, declare friendship after both of their races fought alongside the other at the Ark. He then departed to the Shadow of Intent via Phantom, and joined Rtas 'Vadum on the bridge, both agreeing to return to Sanghelios to "know that it is safe". Thel 'Vadam is given command of the carrier and all Sangheili onboard depart for their homeworld.