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The Fall of Reach
In August 2552, Reach fell to the onslaught of the Covenant. Late in the battle, the SPARTAN-IIs were deployed onto Reach to help defend the planet's orbital defense generators from assault to give the UNSC Navy a fighting chance in the concurrent space battle. During the engagement, many Spartans were killed and more injured, with the majority of survivors eventually retreating to CASTLE Base, including Team Alpha and Team Delta. There, they met up with Doctor Catherine Halsey, who had been escorted to the site by Jun-A266 following the enactment of Operation: WHITE GLOVE on SWORD Base. Here, she worked to enact the operation on CASTLE, destroying all of the AIs present in the facility including Araqiel and Kalmiya, before using self-destruct charges on the base to ensure any materiel inside did not fall into Covenant hands.
In October 2558, a force of artificial intelligences known as the Created, led by Cortana and the Warden Eternal alongside an army of Prometheans, rose up and began to subjugate the Milky Way galaxy. A year following this rise, Blue Team were deployed from UNSC Infinity to CASTLE Base to investigate assets hidden in Halsey's laboratory that may have survived the base's destruction, and help to lead to the defeat of the AI uprising. The team consisted of John-117, Frederic-104, Kelly-087 and Linda-058, who had begun to employ their own variants of the MJOLNIR Powered Assault Armor (GEN3).
The Banished occupiers and UNSC forces withdrew from Reach before Cortana's Guardian arrived. Some troops were left behind on Reach till the end of the Created conflict and the Viery Militia regained control over Arany Basin. Dr. Halsey got the cryobins from CASTLE BASE.
The Banished managed to open the portal on the Menachite Forerunner complex, allowing Atriox and some of his forces travel from Installation 00 to Reach on a Lich, but after this Castor and his Keepers betrayed the Banished and stole their Lich, traveling to the Lesser Ark to fulfill their Great Journey. Unknown to them, the undercover ONI operative Veta Lopis and her Ferret team went with them as well.
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