Battle of Installation 00

The Battle of the Ark was a large engagement between the UNSC-Covenant Separatist Alliance, the Covenant Loyalists, the Flood, and Forerunner Sentinels. It was the final battle of the Second Flood outbreak, the Human-Covenant War, and the Covenant Civil War.

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 12 hrs 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 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. Hood gave Keyes command of the for the Human commitment to the mission and the fleet of ships chased after the Prophet of Truth.

The Battle
The Prophet of Truth, having successfully activated the artifact in New Mombasa, 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 Dawn with a small fleet of Separatist cruisers lead by the carrier Shadow of Intent and proceeded through the Slipspace portal and arrived at the Ark. The Separatists immediately engaged the Brute fleet stationed to protect the Prophet while the Dawn deployed the Master Chief and shock troopers in six Pelicans to locate Truth. Despite being outnumbered 3-to-1 in space, the Separatist fleet made short work of the Loyalist space forces, likely due to the Elites' superior tactical skills. The Brute's tactical ineptness 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 Ship on the Ark although it was never seen again and was specifically said not to take part in the battle above the Ark. Meanwhile, five of the Pelicans 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 AA Gun. After traveling through a small cave with the first Terminal, 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 Longword, a pair of HEVs that had landed and had their occupants murdered, and a crashed Phantom to a battle between Covenant and Sentinels outside a Forerunner Barrier. After meeting another group of marines being attacked, they then moved to the sighted LZ, which was occupied by a pair of AA Wraiths. Clearing the LZ, the Dawn landed. Here, the Master Chief and the ODSTs and marines were reinforced with 3 Scorpion tanks and a Warthog. The human force then fought their way back to the barrier. The Chief went through the upper, smaller doorway while the armor and vehicles (reinforced with 2 more Warthogs and a Gauss Warthog) went through the larger, lower doorway. After activating a light bridge the Spartan went to the other end of the barrier, only to see a Scarab and a Loyalist armored force destroy the 3 Warthogs. Picked up by the Gauss Warthog, and reinforced with two more Gauss Warthogs, he returned to the armored force and led it through 2 Loyalist defense lines of Choppers, Ghosts, Wraiths, and infantry with heavy weapons. When the Scarab returned, the humans then proceeded to destroy it, plus the Choppers and infantry reinforcing it. 343 Guilty Spark, now working with the UNSC-Separatist Alliance, led SPARTAN-117 and the Arbiter, 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. Discovering his location, the Arbiter stole a Banshee and the Chief, with the pair of marines, fought his way past Stealth Brutes and then faced off with a Brute Chieftain and a squad of Jump Pack Brutes before being picked up by Kilo 23. 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 ODSTs' Warthog. The Arbiter and Elites assaulted the second tower. Sergeant Johnson took 4 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 and taken down the second tower, but that Johnson had been attacked. Destroying the Brute defenders outside the third tower with Hornets and Pelicans, Master Chief, the Arbiter, 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 pylons shut down, 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. Fighting through an infestation of the Brutes they had just killed and Johnson's marines, the Elites and the Chief met up with Sgt. Stacker's marines, supported by a Scorpion, a Gauss Warthog, and a Mongoose. While Hornets and Banshees fought overhead, the humans fought to outside the Citadel where the Halos could be activated. Given a another Gauss Warthog and air support from a flight of Hornets and a Pelican, the marines destroyed Banshees, Ghosts, and a Prowler, plus a pair of Scarabs dropped in front of the Citadel by Brutes. Without any heavy support, SPARTAN-117 and the Arbiter 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. With SPARTAN-117 and the Arbiter too far away to stop Truth, Commander Keyes grabbed a Pelican dropship and crashed into the facility to rescue Johnson, but was killed soon after by Truth himself. 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. 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 Master Chief blasted them.

With the Index secure, the Arbiter ordered that the remaining UNSC forces relocate to the Separatist ships and 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, 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, killing Johnson and attacking SPARTAN-117 and the Arbiter. However, by the help of a dying Sgt. 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 Battle 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 (Separatists) 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 surviving brethren departed Earth for their homeworld.

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.

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 cryofreeze 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.

Grunts
It is believed that the surviving Grunts came to peace with the UNSC.

Jackals
It is believed that the surviving Jackals came to peace with the UNSC.

Hunters
It is believed that the surviving Hunters came to peace with the UNSC.

Drones
The surviving Drones are believed to have returned to their homeworld.

Brutes
The surviving Brutes are believed to have returned to their homeworld.

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 on the monument.

The Unknown
It is yet unknown, however, if all the Flood have been destroyed. There are still 5 Installations that have not been found, nor is their status known. It is also not known if the Gravemind followed with all the ships in his command. There was a fleet of hundreds, if not thousands of ships around High Charity. Most of them were presumably destroyed, but there is a possibility that the ship that crash-landed near Voi was not the only ship under Flood control. Additionally, the UNSC military, having barely survived a war that brought them to the brink of annihilation, are barely in a state to defend themselves, much less find and destroy the Halo rings, which means that any roving human or alien with no knowledge of the war or the rings' danger could bring the story full circle. All the Flood that escaped Installation 05 were destroyed including the Gravemind but there still may be more Flood remaining on Installation 05, although any remaining flood on the installation have no way of escaping (It is possible to say that the Elites glassed Installation 05). Furthermore, as the Master Chief and the Arbiter were fleeing Halo, the Gravemind claimed that this defeat would simply be "an addition of time" to a sentence it "never deserved," possibly indicating that a new Gravemind will be formed elsewhere, though it's more likely a threat than an indication of a new Gravemind, though one shouldn't say that the Flood will never return.