Battle of Installation 04

The Battle of Installation 04 refers to a series of skirmishes between the UNSC and Covenant Empire forces on the surface of Installation 04, a Forerunner structure hovering over Threshold. The Flood and the Forerunner Sentinels joined the conflict in the later stages.

Background
Following the UNSC's disastrous defeat at Reach and the loss of a third of her technical staff, the made an apparently blind jump through slipspace from where they would then make their way to Earth. In reality, the slipspace jump was planned by the AI Cortana, using coordinates found in an artifact found on Sigma Octanus IV. The Autumn and the approximately 1,100 humans on it were followed, and upon arriving in orbit above the planet Threshold on September 19, 2552, were intercepted by the pursuing Covenant warships.

Prelude to battle
Prior to landing on the Forerunner construct, the Autumn engaged with its interceptors and managed to destroy four of the Covenant warships. One of the intercepting warships, the Truth and Reconciliation was heavily damaged by the engagement and forced to retreat for repairs.

As Covenant forces began boarding the Autumn, Captain Jacob Keyes ordered Chief Petty Officer Thom Shephard and Petty Officer Third Class Samuel N. Marcus to release Master Chief Petty Officer John-117 from his cryo-chamber. Both officers were killed by Covenant invasion forces while preparing the SPARTAN-II for immediate combat. As the situation became severely out of hand, Captain Keyes initiated the Cole Protocol Article 2 and subsequently Captain Keyes entrusted John-117 the safety of Cortana. With the evacuation order in effect, the human personnels began evacuating the ship using available Bumblebee lifepods and Pelican dropships. Like other personnels, the SPARTAN-II immediately evacuated the ship to the recently discovered Installation 04 aboard a Bumblebee lifepod. The ODSTs, led by Major Antonio Silva, evacuated the ship by means of SOEIV.

To avoid its evacuating personnel from being shot down by the Covenant warships, Captain Keyes manned the Autumn manually, diverting all Covenant attention to the ship as it plummeted towards the Forerunner construct. As the ship was shot down by Covenant warships, most of the cryo-chambers, including Linda-058's, were ejected as per standard UNSC procedure. Upon landing on the construct, the human personnels aboard the ship were captured and executed by the Covenant, save for a few fortunate ones and Captain Keyes, who was taken for interrogation.

Capture of Alpha Base
The ODSTs, having successfully survive the landing on the Forerunner construct, made contact with their officer in command and established a temporary base of operations. Relying on the data AI Wellsley provided, Silva instructed Lieutenant Melissa McKay to take command of a fireteam fo ODSTs and capture a Covenant-held butte to gain tactical advantage in fighting off the Covenant forces. Before McKay departed for her mission, the temporary base of operations was assaulted by Covenant ground forces consisting of 50 Sangheili, 100 Ghosts and, later, Banshees. The defending ODSTs managed to fend off the assault but suffered a loss of 23 ODSTs killed and 16 ODSTs wounded.

After the Covenant assault, Lieutenant McKay proceeded under the order of Major Silva to lead a small contingent of the ODST battalion to the ground assault of Alpha Base. Meanwhile, Major Silva began loading several companies of ODSTs onto Pelicans for aerial insertions.

In the assault, the ODSTs advanced into the butte using a spiraling ramp. Covenant forces responded to this advancement by raining down plasma grenades and unleashing volleys of plasma bolts. The Covenant defense was soon relaxed when a number of ODST companies performed aerial assaults on the defending Covenant forces. McKay's advancement into the butte was halted by a rockfall. Fortunately, McKay managed to find an access into the butte which led to a chamber filled with Covenant explosives. The lieutenant fired a rocket into the chamber, subsequently killing any Covenant force, and led her ODSTs on a lift up to the surface, where they met Major Silva who had arrived and eliminated the remaining Covenant forces.

Rescue of stranded survivors
In a disarray state, several evacuating UNSC personnels eventually landed on the Forerunner construct. Some were killed in the landing while others attempted to get hold of one another and survive the Covenant patrols.

After crash-landing on the Forerunner construct, SPARTAN-II John-117, the sole survivor of the crash-landing of Lima Foxtrot Alpha 43, headed out to get away from Covenant patrols and, under the instructions provided by Cortana, attempted to establish some contact with any surviving human personnels. After evading several patrols and a brief skirmish with a small Covenant lance, John-117 managed to find a group of survivors defending themselves against the aggressive Covenant forces in a Forerunner structure. John established contact with Staff Sergeant Johnson and the survivors, and assisted them in eliminating and defeating the Covenant forces, later reinforced by three waves. Foe Hammer of Echo 419 soon arrived to retrieve the survivors after the elimination of Covenant forces. Witnessing three lifepods flying overhead, Cortana instructed Foe Hammer to disengage her Warthog to support the SPARTAN's efforts in retrieving and securing the survivors. Two Marines assisted the SPARTAN in the rescue efforts.

After successfully rescuing the survivors from all three lifepods, Cortana informed everyone of her findings after hacking into the Covenant BattleNet; Captain Keyes and a number of personnels survived the landing on the installation but have been captured by Covenant forces. The survivors eventually returned to Alpha Base to devise a rescue plan for the captain.

Rescue on the Truth and Reconciliation
The surviving human personnels launched a mission to recover Captain Keyes, who was being held aboard the CCS-class battlecruiser the Truth and Reconciliation. Under the cover of night, John-117 and a fireteam of ODSTs boarded the ship via its gravity lift. After several brief engagements aboard the ship, the rescue team managed to establish a secure control of the ship's command center. John-117 went ahead and freed Captain Keyes and several other captured Marines. When they returned to the command center, they found out that the ODSTs have been slaughtered by Stealth Sangheili. Furthermore, Echo 419 was unable to retrieve the rescue party due to Covenant air patrols. Following Cortana's suggestion, Captain Keyes manned a Covenant dropship and returned everyone to Alpha Base.

Battle of the Silent Cartographer
Using the intelligence gathered by Captain Keyes and Cortana, the human forces amassed a squadron for an assault on the Silent Cartographer island, in their attempt to uncover more information of the installation. John-117 and a handful of Marines, supported by Echo 419 and Bravo 22, penetrated the Covenant defenses, journeyed deep within the island's chambers and access-ways, and discovered the location of the installation's control room.

Events leading to the discovery was not easy; the Covenant managed to temporarily lock access to the chambers within the island, prompting John-117 and the Marines to navigate to the island's security chamber. As they deactivated the security, Bravo 22 and its payload fell prey to Covenant defenses.

Flood Containment Facility
At the same time of the Battle of the Silent Cartographer, Captain Keyes, supported by 2nd Squad and Pelican dropship Victor 933, devised a plan to infiltrate a presumed weapon cache within a structure, as per intelligence gathered from a captured Sangheili. They later met up with Fire Team Charlie, led by Staff Sergeant Johnson, which had proceeded to the structure and engaged the Covenant forces they encountered in the upper levels of the facility. After receiving a transmission from a trouble Marine present further into the facility, they set out to provide aid.

While exploring the lower levels, the UNSC forces came across a sealed door, locked down by the Covenant. With increasing curiosity, the UNSC unlocked the door and explored the Containment Room. Shortly after, Fire Team Charlie was contacted by a distressed Marine requesting for help. Seconds later, the fireteam was attacked by a swarm of Flood Infection forms, infecting the Captain Keyes, Privates Riley, Kappus, Mendoza, Jenkins Bisenti and several others. Two Marines managed to avoid the infection, one of whom was killed just outside and the other who escaped by playing dead. Staff Sergeant Johnson shrugged off the infection forms and manage to escape the facility.

Assault on the Control Room
After the Battle of the Silent Cartographer, Cortana instructed Foe Hammer to deploy them using navigations she gathered from the discovery of the control room. Alone, John-117 was inserted into a network of tunnels occupied by Covenant forces. The SPARTAN then received a radio transmission from Fire Team Zulu, who were pinned down in a valley, as he fought his way through the network of tunnels. John-117 assisted Fire Team Zulu in eliminating the Covenant forces and its armor support, then journeyed through a system of adjacent canyons until reaching a dead end, where Fire Team Zulu requested to be evacuated.

John-117, with Cortana providing guidance, eventually discovered a large pyramid structure, on top of which was the Control Room. Upon reaching the chamber, Cortana accessed the installation's systems and discovered a terrible secret within the installation. Fearing the safety of Captain Keyes, she instructed John-117 to head for him.

Battle of Alpha Base
While Captain Keyes headed for the "weapons cache" and the SPARTAN went for the location of the control room, Lieutenant McKay staged a raid on the crashed Pillar of Autumn, in order to gain extra supplies to finance the battle effort. The raid was successful; the UNSC forces managed to salvage a squad of Warthogs, trailers and four Scorpion tanks along with food supplies and ammunitions. However, when returning the salvaged vehicles to Alpha Base, the convoy was ambushed by Covenant forces using Wraiths, Banshees and Ghosts. Despite the sizeable Covenant forces, the UNSC forces managed to withhold the ambush and inflict greater damage on the Covenant forces.

The Covenant later returned to assault Alpha Base, initiated by an air insertion and then followed by a ground advancement. Using a captured Pelican dropship and its captured pilot, the Covenant attempted to insert 30 Special Operations Sangheili, led by Special Operations Officer Zuka 'Zamamee to assassinate the apparently absent SPARTAN-II John-117 and clear a landing zone for six Spirit dropships for immediate evacuation. The air insertion was quickly discovered by the human forces on Alpha Base, whom flooded the Pelican dropship with jet fuel before igniting it, killing 24 Sangheili. The six Sangheili managed to escape into the base, neutralizing the human control rooms and liberated the captured Covenant soldiers. However, the MLA auto-cannons and various other defense systems employed by the human forces managed to destroy several incoming Spirit dropships. Despite their numerical superiority, the Covenant forces landing on the butte were soon either killed or captured, and the assault on Alpha Base stalled.

The ground assault, led by a Zealot Field Master Noga 'Putumee, made significant progress against the humans due to their use of Spirit dropships to clear the way ahead of the ground forces. However, the seeming route was designed to lure the Covenant into the firing range of a pair of concealed Scorpion tanks, which then tore into the ranks of the aliens and inflicted major casualties. Field Master 'Putumee was killed by the third shot from the tanks, throwing the Covenant forces into chaos, and of the 150 infantry with him, only a few survived to retreat. Meanwhile, the surviving Covenant Special Operations team from the air insertion phase and the freed Covenant troops ran into an ambush devised by the Marines in which all members of both sides were killed other than the Zuka 'Zamamee and Yayap, both of which fled in a recaptured Banshee. By this time, however, the Covenant ground assault was in full retreat.

The release of the Flood
Covenant forces around the Flood Containment Facility were in a disarray state due to the release of the Flood. Several dropships were shut down with some captured by the Flood. One particular dropship, the Brilliant Gift, was manned by the Flood towards the Covenant fleet currently hovering over the installation. The dropship eventually crash-landed on an agricultural support ship Infinite Succor and infected its personnels, unbeknownst to those around the Infinite Succor. Supreme Commander Thel 'Vadamee responded by deploying a Special Operations unit led by Special Operations Commander Rtas 'Vadumee. The Special Operations unit engaged with its invading aggressor, eventually leaving Special Operations Commander 'Vadum the only survivor of the engagement. The presence of the Flood and its potential of being space-borne was reported to Supreme Commander 'Vadam.

Three hours after the assault on the Control Room, John-117 arrived near Victor 933's crash site via Echo 418. His travel towards Captain Keyes' last known transmission was met with a considerably small concentration of Covenant forces, which was easily handled. Upon unlocking the door to the Containment Room, he found Private Jenkins' helmet and accessed its video records. Shortly after, John-117 was attacked by the remaining Flood forms that spewed out of nearby chambers. The SPARTAN quickly proceeded to escape the facility, combating Infection and Combat forms. He soon caught up with Corporal Lovik's squad, who were advised by Echo 419 to take refuge at a nearby structure.

The survivors fought their way through the swamp in search of the structure for immediate evacuation. On the site, the survivors were aided by unknown constructs later identified as the Sentinels, under the command of the installation's Monitor, 343 Guilty Spark. The Monitor teleported the SPARTAN into the Library, leaving the other survivors to be evacuated by Echo 419.

The Library and Halo
After discovering a Reclaimer was within reach, 343 Guilty Spark, without hesitance, teleported John-117 into the Library, where he was tasked with the retrieval of the Activation Index. Proceeding into the bowels of the huge structure, the SPARTAN fought off wave after wave of Flood, before the Monitor called in Sentinels to assist him. Upon reaching the central shaft of the Library, John-117 rode another elevator down to the Index to deactivate the security protocols around the Index. 343 Guilty Spark then took over his role and stored the Index within itself. The Forerunner Monitor teleported both back to the Control Room. The pair then proceeded to activate the installation. However, Cortana, who, having spent twelve hours within the installation's systems, had discovered the installation's true purpose, stopped the firing systems. The UNSC AI then revealed the installation's true purpose to the SPARTAN. 343 Guilty Spark, unable to purge Cortana from the installation's system due to her having merged with the Index, instructed its Sentinels to apprehend the SPARTAN and retrieve the UNSC AI from the SPARTAN's helmet.

John-117, after destroying the Sentinels and eliminating the patrolling Covenant forces, followed Cortana's instructions to destroy the three Phase Pulse Generators to delay the firing process, should the Monitor manage to circumvent the firing protocols. Upon the destruction of the third generator, Cortana suggested to destroy Halo to prevent future use of the installation by enabling the Autumn 's self-destruct system. She then experimented the teleportation grid by teleporting the two to the damaged Truth and Reconciliation to rescue Captain Keyes to obtain the proper authorisation.

Ambush on the Covenant
At the same time, Major Silva proposed to engage the Covenant forces in a medium conflict and instructed Lieutenant McKay to plan out the operation. McKay decided to the burned our remains of Charlie 217, mock-injured Marines, and a phony distress call as baits to lure the Covenant into an ambush. This operation was further strengthened when Wellsley informed them of the Covenant's increased interest in intelligence gathering by monitoring the radio traffic and conducting reconnaissance flights after the human raid on the Truth and Reconciliation.

The operation begun when the human forces "informed" a patrolling Banshee of their location. When the Banshee retreated presumably to report its findings of the human location, the human forces abandoned their mock location and waited for the incoming Covenant forces. The first wave was a Spirit dropship with a lance of Unggoy, Kig-yars and Sangheili along with a pair of Hunters. The first wave was handled rather quickly; Lieutenant McKay ordered those with heavy weapons to concentrate on the Hunters before engaging the lance. Soon, the dropship returned and unleashed volleys of plasma on the entire area, forcing the human forces to take cover. Covenant ground forces were deployed as the dropship retreated and began engaging the human forces into the rocks. The human snipers managed to eliminate five Covenant soldiers before the dropship exacted the position; unfortunately, their positions was exposed and resulted with two snipers killed and one wounded by plasma fire. The operation turned awry as the Covenant had the advantage over the human forces' territory.

Just as Lieutenant McKay about to issue a retreat order, both forces were attacked by a newer force, the Flood. While the Covenant had some experience in combating the Flood, the human forces had none. Both forces were in a disarray state and were massacred by the Flood; while the Combat forms slash their way through, the Infection forms burrowed themselves into corpses and helpless victims and turned them into potential Flood forms. In the ensuing horror, Lieutenant McKay was confronted by Jenkin, now a Combat Form with limited control of his body and urging for someone to kill him. The lieutenant, however, disarmed and restrained the Flood form, hoping to use it as a specimen to study the Flood. The Flood attack forced both human and Covenant to join forces and fend off the Flood. After successfully eliminating the Flood threat, both groups returned to killing one another. At the end, the human forces claimed a pyrrhic victory with heavy casualties.

Raids on the Truth and Reconciliation
After getting teleported by Cortana within the halls of Truth and Reconciliation, John-117 continued with his objective in rescuing Captain Keyes and have him to authorise the self-destruction of the Autumn. The pair found themselves in the middle of an ongoing battle between Covenant forces and the Flood forms for the control of the damaged battlecruiser. The SPARTAN fought his way through waves of Covenant and Flood forces and arrived at the bridge where Keyes is located. The pair soon discovered that the captain had turned into one of the Flood, a Proto-Gravemind. With no other choice, John-117 forcefully obtained the captain's command neural interface from his skull and quickly retreated for the Autumn via Banshee.

By September 22nd, only 312 humans (236 Marines and 76 naval personnel) remained alive at Alpha Base. In order to escape back to Earth, it was proposed that they capture the Flood-infested Truth and Reconciliation. Despite the AI Wellsley's warnings, the humans proceeded with the attack and established control of crucial chambers within the ship. The Flood forces aboard the ship was momentarily hold off from gaining access to the secured chambers, allowing the human captors time to commandeer the ship for interstellar travel. Several attempts were made by the Flood to infect the human captors but were quickly taken down. Lieutenant McKay, worried of potential Flood attacks, urged Major Silva to eliminate the Flood aboard the ship before leaving for space, but this suggestion was refused by the major without hesitance. the lieutenant then proceeded in sabotaging the ship's system by severing the fiber-optic passage connecting the engines to the command center, knowing that the Flood threat would severe and fatal for those on Earth. The ship was destroyed shortly after.

Destroying the Autumn
John-117 promptly returned to the Pillar of Autumn using a Banshee he commandeered back in the Truth and Reconciliation. The SPARTAN, through Cortana's instruction, fought his way to the ship's bridge. The UNSC AI started the ship's self destruct sequence, only to discover to her dismay that the Forerunner Monitor halted the sequence. Cortana deduced that the Monitor was in Engineering and was trying to take the Autumn 's engines offline. John-117 decided to overload the engines by manually cracking the engine's magnetic containment fields.

The SPARTAN fought his way through Cryo B to reach Engineering. Following Cortana's instructions, he destroyed each of the four engines by launching explosives into the open shafts, destabilizing the containment fields. Cortana calculated that the pair had 15 minutes to evacuate the ship before the engines detonated. The SPARTAN headed for the shaft of elevator V-1269 where he was ambushed by Zuka 'Zamamee. The trap almost succeeded, but with Cortana's help, the SPARTAN killed Zuka 'Zamamee by knocking the Sangheili to the bottom of the shaft. John-117 then rode the elevator to a Class Seven Service Corridor located along the ship's dorsal structure. Using a Warthog, he drove along the length of the Corridor to External Access Junction 4C where Echo 419 was to pick the SPARTAN up one last time. However, two Banshees shot down the Pelican, killing Foe Hammer. John-117 was then forced to drive to Launch Bay Seven, where a single Longsword fighter was docked. The SPARTAN successfully boarded the ship and escaped Halo. Moments later, the Autumn 's engines detonated, destroying Halo and bringing the battle to an end.

Aftermath
After the destruction of Installation 04 and John-117's successful escape, Cortana scanned the installation's debris field for survivors. Soon, multiple Covenant capital ships entered the system. Cortana discovered several cryo pods jettisoned from the Pillar of Autumn during the initial battle, one of which contained Linda-058, and a Pelican dropship with several survivors. John-117 picked up the survivors in the Longsword, and with their help, boarded and hijacked the Covenant flagship Ascendant Justice and headed for Reach.

From a strategic standpoint, the Battle of Installation 04 was a major victory for the UNSC. The Covenant lost dozens of ships and many thousands (possibly hundreds of thousands) of ground troops, while the UNSC lost only one ship and perhaps little over a thousand troops. Furthermore, the UNSC gained tactical information on Covenant technology, and more importantly they learned about the Flood and the purpose of the Halo Array.

The battle on Alpha Halo resulted in more than just a UNSC victory, however. It sparked a series of events that would alter the course of the entire war. Thel 'Vadamee, the Supreme Commander of the Fleet of Particular Justice, was stripped of rank and branded as a heretic for his failure to protect Halo. Instead of executing 'Vadamee, however, the Prophet of Truth made him an Arbiter. The Arbiter would play a major role in the events of Halo 2 and Halo 3, as would 343 Guilty Spark, who survived Halo's destruction. Furthermore, outside the galaxy, the Ark started to construct a new Halo to replace the one destroyed in the battle. It was on this replacement Halo that the final battle of the war would take place.

Survivors
It is assumed that only eight members of the Pillar of Autumn were in space and therefore survived the blast, six of which were on a Pelican, two SPARTANs, Linda-058, who was in a Cryo pod, and the other one, John-117, was on a Longsword fighter. John-117 managed to retrieve three tubes, one containing Linda. The people in the other two had died in sleep due to malfunctions. It is not known whether this was a malfunction in one of the cryo storage rooms, or if it happened to almost every tube. Every other person at the battle presumably died when Installation 04 was destroyed. However, since Gunnery Sergeant Pete Stacker and Private Chips Dubbo, among others, have been seen again in later games, it can be assumed that there were other survivors.

However, it is explained in Halo: The Flood and Halo: First Strike, that the Autumn was operating as a skeleton crew, as the remaining non-essential crew remained in cryo. When the Covenant infiltrated the ship, most of the crew were still asleep and their tubes were shot into space to save them from being killed in the crash.

UNSC

 * Pillar of Autumn staff:
 * Crew
 * Captain Jacob Keyes
 * Lieutenant Commander Gail Purdy
 * Lieutenant Dominique
 * Lieutenant Hall
 * Lieutenant Elias Haverson
 * Lieutenant Aki Hikowa
 * Ensign William Michael Lovell
 * Chief Petty Officer Thom Shepard
 * Petty Officer First Class Mary Murphy
 * Petty Officer Third Class Cho
 * Petty Officer Third Class Sam N. Marcus
 * Petty Officer Third Class Pauley
 * Crewman Abiad
 * Crewman Singh
 * Crewman Wang
 * Flight Crew
 * Crew Chief Cullen
 * Flight Officer Captain Carol Rawley
 * Flight Officer Mitchell
 * Warrant Officer Shiela Polaski
 * Lieutenant "Cookie" Peterson
 * Lieutenant Rick Hale
 * Lieutenant Frye
 * Ensign Ellen Dowski
 * SPARTAN-IIs
 * Master Chief Petty Officer John-117
 * Linda-058
 * Marines
 * Major Antonio Silva
 * First Lieutenant Melissa McKay
 * Second Lieutenant Dalu
 * Second Lieutenant Oros
 * Master Sergeant Lister
 * Gunnery Sergeant Pete Stacker
 * Gunnery Sergeant Waller
 * Staff Sergeant Avery Johnson
 * Staff Sergeant Marvin Mobuto
 * Sergeant Tink Carter
 * Sergeant Corly
 * Sergeant Parker
 * Corporal Locklear
 * Corporal Lovik
 * Corporal Wilkins
 * Lance Corporal "Snaky" Jones
 * Private First Class Chips Dubbo
 * Private First Class M. Fitzgerald
 * Private First Class Hosky
 * Private First Class Wallace A. Jenkins
 * Private First Class Suzuki
 * Private Bisenti
 * Private Kappus
 * Private Manuel Mendoza
 * Private Marie Postly
 * Private Riley
 * Private Satha
 * Al-Thani
 * Dawkins
 * "Doc" Valdez
 * Murphy
 * Yutrzenika

Covenant

 * Fleet of Particular Justice
 * Supreme Commander Thel 'Vadamee
 * Prophet of Stewardship
 * Ship Master Orna 'Fulsamee
 * Zuka 'Zamamee
 * Field Master Noga 'Putumee
 * Councilor Soha 'Rolamee
 * SpecOps Commander Rtas 'Vadumee
 * Sub-Commander Bero 'Kusovai
 * Yayap
 * Gagaw
 * Linglin
 * Igido Nosa Hurru
 * Ogada Nosa Fasu

Forerunner constructs

 * 343 Guilty Spark

Flood

 * At least one Proto-Gravemind