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.

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.
 * 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 Type-27 Banshees. 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.
 * Deployment (D)+00:03:24: Major Silva's Single Occupant Exoatmospheric Insertion Vehicle is among the first to enter Installation 04's atmosphere.
 * D+00:02:51: 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.
 * D+00:05:08:
 * 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.
 * 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+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.

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.
 * D+44:38:19: Field Master Noga 'Putumee ambushes the returning convoy led by Lt. McKay, but is ultimately unsuccessful in his attempt.

October 20

 * Raid on the Threshold gas mine: