Aftermath of the Fall of Reach
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Losses and retreats
Numerous ships and units were destroyed or were irreparably damaged. The UNSC Basra, one of the finest in service was damaged beyond repair. One of the most revered ships in the fleet and the Flagship of the Epsilon Eridani Fleet, the UNSC Trafalgar, was also destroyed.
Escape of the Pillar of Autumn and Installation 04
The UNSC Pillar of Autumn would flee the battle, with the AI Cortana commandeering it's escape destination to the previously undiscovered fourth Forerunner Halo. While the Battle of Installation 04 was tangential to the main front, the containment of the initial Flood outbreak - and the experience gained - was just as critical for the survival of humanity.
ONI artifact recovery and assessment
Artifacts and other recovered items
During and after the Fall of Reach, a number of artifacts were recovered. Prior to the completion of Operation: WHITE GLOVE, ONI recovered Dr. Halsey's personal journal. As well, a flag that was originally used by SPARTANs during training sessions of Capture the Flag, was recovered and put on display at Outpost Discovery.
Investigations and analysis of the battle
On September 4, 2552, the Office of Naval Intelligence began investigating Joseph Poteet and Alasdair Schicker, believing that they may have leaked classified information to the Covenant. Including the location of Reach. At the same time, Lieutenant Wagner who escaped the battle reported to the UNSC Security Council at HIGHCOM Facility Bravo-6, Earth, detailing the glassing of the planet and the escape of the UNSC Pillar of Autumn.
An inquiry was held by ONI Retrieval and Acquisitions on September 26, 2552 which culminated in the creation of a target profile of Thel 'Vadamee by Lieutenant Commander Jameson Locke. This report included information on Thel's actions at the Fall of Reach.
Just over a month after the battle on October 8, 2552, Admiral J. Garcia compiled 844 files into a report called "Prelimenary Reports of Action - Defense of Reach". It detailed fleet actions in the Reach Defense Coordination Zone. This report along with several others would be assembled into another file in 2554 for Fleet Admiral Terrence Hood.
Earth and the Sol system
The Office of Naval Intelligence knew of at least four Covenant battle groups centred around large assault carriers prowling the outer edges of UNSC-held space. The Navy believed that the location of Sol was compromised and began relocating heavy industry facilities and command centers out of the system in a long-planned exodus. UNSC units were also posted in Earth's tether cities following the battle of Reach. Some graffiti on Earth used the slogan "Remember Reach".
Post-fall missions and activities on Reach
As the Covenant began glassing Reach, the surviving Spartans continued their fight. Team Gamma; a Red team splinter composed of Anton-044; Grace-093 and Li-008, had managed to survive and complete their mission to rescue Vice Admiral Danforth Whitcomb from HIGHCOM. Too late to reach CASTLE base, they hid in the mountains attacking Covenant units with the use of guerrilla tactics as opposed to a conventional assault. They programmed their MJOLNIR suits to transmit the "Oly Oly Oxen Free" secret code on E-Band radio, hoping that any surviving Spartans would discover it and help them.
Meanwhile underneath the ruins of CASTLE base, Dr. Halsey and five Spartans (Fred, Kelly, Will, Vinh, and Isaac) had spent five days combing the remains of a Forerunner structure and an additional five days trapped in a hallway inside the ruins by Covenant forces. They managed to retrieve a Forerunner crystal that the Covenant were seeking, but it emitted a burst of radiation which alerted the Covenant to their presence. Vinh and Isaac fell at the hands of overwhelming Covenant forces, and the others escaped by blowing the hallway down behind them.
After the survivors were recovered by Ascendant Justice, a Covenant Flagship captured by John-117 after the Battle of Installation 04, the ship drew a group of Covenant vessels out of the system in pursuit to Eridanus Secundus, leading to the destruction of the asteroid colony, and the destruction of the artifact and the recovery of only a small number of pieces by the Covenant. The Ascendant Justice also destroyed around sixteen Covenant warships during the escape in slipspace and at the rebel base.
Environment, livability and future of Reach
Reach would return to a green state by 2589 and with at least one colony ship coming to settle on the planet. By 2610, the city of New Alexandria was resettled with a few new areas including Hősök tere, which held the Reach War Memorial.