Timeline of the Battle of Installation 04

This is a timeline of the events slightly before, during, and slightly after the Battle of Installation 04. The battle primarily lasted between September 19 and September 22, 2552, though notable skirmishes and engagements took place before and after this timeframe. Concurrently with these events, the final stages of the Fall of Reach were taking place.

July 17–18

 * Battle of Sigma Octanus IV. Blue Team recovers an artifact.

August 24

 * Doctor Catherine Halsey is shown a hologram of the Sigma Octanus artifact, and suggests that it bears similarities to hypothesised navigational code in enemy transmissions. Halsey also notes that the object shares many language and code forms found on the large Forerunner artifact buried under SWORD Base on Reach.

August 27

 * AI Cortana is split, with several fragments tasked with analysing the data from the Sigma Octanus artifact and the Babd Catha structure. Cortana would translate these symbols as coordinates, though their meaning and the significance of the object located there remains unknown.

August 29

 * NOBLE Team extracts the Cortana fragment from Cortana from SWORD base.

August 30

 * The Cortana fragments are escorted to the Asźod ship breaking yards, and reunited aboard the . John-117 and Linda-058 are deployed to Reach orbital station Gamma to purge the navigational databanks of the, and Linda is critically injured, being stowed in a cryo pod aboard the Autumn until such a time as she is able to receive medical treatment. The rest of the Spartan-IIs tasked to the Pillar of Autumn are deployed on the ground to defend Reach, leaving John-117 the only operational Spartan supersoldier on the ship.
 * The Autumn breaks the Covenant blockade of Reach and initiates an emergency random slipspace jump, as per the Cole Protocol. However, Cortana subsitutes the intended random coordinates with the ones gleamed from her research.
 * The Fleet of Particular Justice, led by Thel 'Vadamee, follows the Pillar of Autumn.

Unknown date

 * The Fleet of Particular Justice arrives in the Soell system ahead of the Pillar of Autumn thanks to their superior slispace drive technology.
 * Particular Justice establishes its vessels on the far side of the ring and establishes several recon pickets to await the Autumn.
 * The Minor Prophet of Stewardship declares this mission as religious matter as opposed to a military one, and invokes immediate adherence to reclamation procedure. The Prophet and Thel 'Vadamee convene aboard the Seeker of Truth to contact High Charity and ensure their interpretation of Covenant scripture is accurate, though High Charity cannot be reached and no decision is made. 'Vadamee is reluctant to give up command.
 * The Undiminished Entelechy and Purity of Spirit are secretly ordered by the Prophet to begin sweeping the ring and its outlying installations for technology.

September 18

 * 2200 hours (ship time): Captain Keyes and other key crew wake up on the UNSC Pillar of Autumn, and check the status of the ship.

September 19

 * The Pillar of Autumn exits slipspace to discover a dozen CCS-class battlecruisers divided into battle groups of four vessels already securing the system. The Prophet of Stewardship orders that the Covenant fleet is not fire on the human vessel, but instead launch fighters and boarding parties for fear of damaging the holy ring. 'Vadamee ignores this order, and opens fire on the human cruiser.
 * 0103 hours (ship time): Chief Petty Officer Thom Shephard rouses Petty Officer Third Class Samuel N. Marcus via intercom and requests he report to Cryo Two.
 * 0115 hours (ship time): The bridge crew of the Pillar of Autumn assemble on the bridge to await them leaving slipspace in 5 minutes, where Captain Keyes asks Cortana to shut down all systems before returning to normal space.
 * 0120 hours (ship time): The Pillar of Autumn exits slipspace in the Soell system.
 * 0127 hours (ship time): The suffers its first hit since fleeing Reach due to a Seraph powering down and managing to slip past its sentry ships. Nonetheless, the ship's GA-TL1 Longsword escort is able to pick off the last of the Covenant recon pickets. Captain Jacob Keyes initiates Article 2 of the Cole Protocol, ordering the crew to abandon ship. He orders Thom and Samuel to "unseal the hushed casket" and awaken John-117. The Spartan is ordered to evacuate ship with Cortana, while Keyes stays behind to crash-land the ship on the surface of the ring.
 * Fireteam Raven is ordered by Major Antonio Silva to defend the Pillar of Autumn from boarders. They fight alongside the ship's Marine complement to fend off boarders, before being tasked by Wellsley to man the ship's M910 Rampart point defense network and fend off several waves of inbound Morsam-pattern Seraphs and s. Raven eventually make their way back to their SOEIV bays and evacuate the ship.
 * The Minor Prophet of Stewardship orders the deployment of an Ossoona, Isna 'Nosolee, to board the Autumn to obtain useful information.
 * John-117 and Cortana escape the Autumn in a Class-3 Bumblebee lifeboat, designated Lima Foxtrot Alpha 43.
 * Carol Rawley and several other Pelican pilots are able to escape the Pillar of Autumn.
 * Keyes sets the Autumn on a collision course with the ring, and prepares to board lifeboat Kilo Tango Victor 17. He is followed by 'Nosolee, who is ultimately shot by Keyes' M6D magnum.
 * D+00:02:51: Lima Foxtrot Alpha 43's pilot guides it into a shallow dive toward Installation 04's surface but an airbrake failure causes all Marine personnel aboard the craft to die. The Spartan moves into the hills to evade Covenant patrols. The Master Chief begins to round up Marine survivors, who are brought back to Alpha Base by Echo 419.
 * Deployment (D)+00:03:24: Major Silva's Single Occupant Exoatmospheric Insertion Vehicle is among the first to enter Installation 04's atmosphere.
 * D+00:05:08: Kilo Tango Victor 17, containing the Pillar of Autumn bridge crew lands on the ring. Keyes and company begin making their way to safety, but are eventually captured by the Covenant after several hours.
 * Most of the 130-strong Orbital Drop Shock Trooper complement of the Pillar of Autumn lands on the ring and immediately sets to work securing a fortified Forerunner mesa under the supervision of Major Silva and Lieutenant Melissa McKay. B Company sets out during the night to capture the butte, while C Company rendezvouses with the escaped Pelican shuttles. A Company and D Company are attacked by a force of Covenant ghosts.
 * Fireteam Raven land on the ring and begin making their way to the crash site of the Pillar of Autumn under the guidance of Wellsley, a journey expected to take 28 hours.
 * D+03:14:26: John-117 encounters Fire Team Charlie holding out in the structures of Alpha Halo. He assists the team before Echo 419 arrives to extract the marines. He spends the remainder of the afternoon rounding up survivors before heading to Alpha Base.
 * D+17:11:04: Raid on the Truth and Reconciliation begins as UNSC forces led by John-117 storm the vessel and rescue Captain Jacob Keyes. A secondary team under Lieutenant Dalu extracts a number of Covenant supplies for use by Alpha Base including six Shade turrets.
 * B Company is inserted onto the planes surrounding the Pillar of Autumn at night.
 * In response to the succesful raid on the Truth and Reconciliation, Zuka 'Zamamee is given permission to hunt down John-117.


 * Unknown time (post-space battle): Minor Prophet orders artifact retrieval teams led by Loka 'Bandolee and Sesa 'Refumee to investigate the gas mines of Threshold. Fleet master 'Vadamee issues a transmission ordering all military forces to be concentrated on the human threat. The Prophet sends secondary and tertiary teams to a Flood containment facility, and prepares to send a fourth following their loss of contact. 'Vadamee issues a second order to no response from the Prophet, leading to his deployment of a single infantry unit to the carrier. Ascendant Justice shoots down the craft, and the Prophet warns that future interference will be met with the same fate.

September 20

 * D+28:15:25: Raid on the Pillar of Autumn begins at dawn, led by Lt. McKay. The ODST company storms the Pillar of Autumn and takes the meager Covenant force by surprise and begins offloading supplies.
 * Fireteam Raven join a UNSC armored convoy headed to the crash site of the Autumn and assist in the battle.
 * The Battle of the Silent Cartographer begins as the Master Chief and Cortana begin to search for Halo's map room. Zuka Zamamee unsuccessfully attempts to kill the Spartan, but the battle is ultimately successful for the UNSC.
 * Captain Keyes, Second Squad and Fire Team Charlie deploy to a Flood containment facility on the ring to search for a supposed Covenant weapons cache, leading to a massive Flood outbreak.
 * Sergeant Avery Johnson is able to escape the Flood threat.
 * D+44:38:19: Field Master Noga 'Putumee ambushes the returning convoy led by Lt. McKay, but is ultimately unsuccessful in his attempt.
 * Echo 419 lowers into the tunnels in the middle of the Silent Cartographer island, depositing the Master Chief near the ice canyons where the ring's Control Room is located. John proceeds to assault the control room with Fireteam Zulu. At Cortana's insistence, the Spartan departs to rescue Captain Keyes while she stays in the system.
 * D +58:36:31: Echo 419 deploys John-117 into the swamps of Installation 04. The Spartan witnesses the Spirit dropship Brilliant Gift escaping the swamps. The Master Chief encounters the Flood and narrowly escapes the swamps with the help of 343 Guilty Spark.
 * Brilliant Gift crash-lands on the Infinite Succor, a serving the Covenant fleet. The Flood aboard the dropship proceed to infect the vessel, leading a special operations team led by Rtas 'Vadumee to board the ship to eradicate the infestation. The Minister of Etiology is infected, and Vadumee's left mandibles are cut off.
 * 7th Cycle, 49 Units (Covenant battle calendar): Sangheili Soha 'Rolamee is executed by the Prophet of Stewardship for his failure to contain the Flood outbreak, and is used as a warning to Zuka for repeated failure. The Fleet Master prepares a boarding action to relieve the Prophet of command.
 * UNSC forces recover Yayap, as a prisoner-spy, and take him to Alpha Base.
 * 'Vadamee orders quarantine procedure to be enacted amongst the fleet, shooting down any ship which fails to return biometric scans for its crew. Undiminished Entelechy is among the vessels destroyed by the action.
 * Prophet of Stewardship moves his headquarters from the Ascendant Justice to Truth and Reconciliation, ordering the local crew to police the ship and detain anyone who poses a threat - including the Fleet Master. 'Vadamee boards the ship and reaffirms the crew's loyalty to him, with no shots fired.

September 21

 * 0236 hours: The last scheduled mission for the night returns to Alpha Base. Several hours later, Pelican Charlie 217 radios in, requesting permission to land. The Pelican is given permission despite having not been heard from since the initial landings, and Wellsley realizes too late; the Pelican is staffed full of Special Operations Sangheili, and the Battle of Alpha Base begins.
 * Fireteam Raven is ordered to defend Alpha Base. They eliminate several waves of troops before being recalled to the canyons near the control room to assist the Master Chief.
 * D +60:33:54: Echo 419 attempts to extract the Master Chief from the Flood containment facility, but he is instead teleported away by 343 Guilty Spark to the Library, where he retrieves the Index.
 * The Master Chief spends the next seven and a half hours fighting Flood combat forms on his way to the Index.
 * D +68:03:27: 343 Guilty Spark teleports the Master Chief back to the Control Room after retrieving the Index. Cortana reveals to Chief that activating Halo would wipe out all life in the galaxy.
 * Master Chief leaves the Control Room and uses his armor's power to deactivate three pulse generators to delay Halo's firing. Fireteam Raven is redirected from Alpha Base to the canyon to assist the Master Chief in his mission. A wraith damages their falcon while they leave the canyon.

September 22

 * D +73:34:16: Cortana used Installation 04's teleportation grid to teleport the Master Chief back to the Truth and Reconciliation to retrieve Captain Keyes's neural lace.
 * Following the Master Chief's second raid on the Truth and Reconciliation, human forces lead by Major Silva successfully claim the ship. Lieutenant McKay creates an explosion that destroys the ship, stopping the Flood from stowing away to Earth.
 * Fireteam Raven crashland near a Forerunner structure. They fight off Flood until they can be extracted.
 * D +76:18:56: The Master Chief and Cortana arrive at the Pillar of Autumn crash site in a captured banshee. Fireteam Raven arrives to halt the advance of a scarab moving towards the crashsite.
 * Fleetmaster Thel 'Vadamee orders all ships to take cover behind Threshold to avoid being damaged by the impending explosion of Installation 04.
 * 1637 hours (military calendar): Master Chief has Cortana scan the debris field of Installation 04 after several failed attempts.
 * 1710 hours (military calendar): Master Chief links his longsword with a pelican full of survivors of Installation 04. He pulls a gun out on Sergeant Avery Johnson, assuming he must have been infected by the flood based on the footage from Private Jenkins's recorder chip. Cortana convinces the Master Chief to trust Sergeant Johnson.
 * 1750 hours (military calendar): The Master Chief and other survivors use the longsword to board the Covenant flagship Ascendant Justice.
 * 1802 hours (military calendar): The Master Chief engaged in combat with a sword wielding elite. With help he managed to would the elite and send it out of the ship in an escape pod.
 * 1827 hours (military calendar): Cortana pilots the Asendant Justice into Threshold's upper atmosphere to evade other Covenant ships in the system. From there she uses the ship's superior Covenant slipspace drive to travel back to the Epsilon Eridani system despite the gravitational influence of Threshold.

October 20

 * Raid on the Threshold gas mine:

Additional reading
Several official timelines of the Battle of Installation 04 have been published by 343 Industries. They are linked below for convenience.

Internal links

 * The Halo Conflict - Halopedia archive of a timeline recounting of the Battle of Installation 04 formerly posted on Halo Waypoint.
 * The Halo Conflict timeline - Halopedia archive of a now-defunct Halo Waypoint universe article originally at this link.
 * Priority Broadcast Log/Eleventh Cycle, Third Unit - A timeline of the battle told from the Covenant perspective, as detailed in the Adjunct of the 2010 release of Halo: The Flood.
 * Data Drop #3 - A data drop included in the Halo Legendary Crate detailing some of the interactions between Fleet Master Thel 'Vadamee and the Minor Prophet.