First Battle of Installation 01

he First Battle of Installation 01 was an engagement of the Forefather War. It took place between the Eleventh and the Seventeenth of December, 2560.
== Background ==
In early December of 2560, the S'southi military leader Sark was informed of the existence of the Halo array by Binding Enlightenment, their "god" and leader of the Forefathers. Binding Enlightenment did not know the location of each ring, only that of Installation 01 through the usage of the Luminary on Propriety, and delivered orders to Sark to travel to the ring.
Installation 01, and the other rings in the array, were of great importance to the Forefathers, and by extension, the S'southi, as the Forefathers wished to use them to "gain their ultimate revenge against the sons and daughters of the Forerunners", and sought to fire the entire array and purge the Milky Way of life.
The S'southi arrived at Installation 01 on the Ninth of December, and they began attempts to search for the sacred icon. Upon the realisation that the Installation's monitor, a Forerunner construct, was still active, Binding Enlightenment became blinded by rampant rage and ordered Sark to destroy all active constructs on the ring, including the Sentinels. The ensuing battle between the S'southi and the Sentinels bogged the S'southi down and prevented them from locating the index. The monitor, 001 Anguished Deliberation, would send an urgent communication to the array and the Lesser Ark, informing them of the threat currently posed to the installation. 
Human scientists on Installation 03 reported these communications to the Galactic Alliance, which dispatched a sizable military force, primarily consisting of starships, to Installation 01. They would arrive on the Eleventh of December.
== Engagement ==
=== Assault on the Cartographer ===
The S'southi had controlled the Cartographer since their arrival on the Installation, being one of the first locations they had managed to fully occupy. However, 001 Anguished Deliberation had thwarted their attempts to locate the Activation Index by remotely disabling the Cartographer, rendering it useless for the S'southi. Recognising the strategic value of the Cartographer, the Galactic Alliance decided upon a surprise attack on the local garrison.
Galactic Alliance forces were aerially inserted in a two kilometer radius around the cartographer, from which an armoured corps and several infantry platoons engaged scattered S'southi defenses along the perimeter. The S'southi would ultimately be pushed back to the structure itself, where they would hold position for an extended period of time.
Due to the ongoing stalemate, 001 Anguished Deliberation intervened in the battle with a number of Sentinels, engaging the S'southi all throughout the structure and allowing the Galactic Alliance the critical advantage they needed to break through their defenses. In the following two hours, the Cartographer would be cleared of S'southi stragglers and the location of the Activation Index would be provided to the Alliance by the monitor.
=== Scattered Engagements ===
Following the successful assault on the Cartographer, the Galactic Alliance's ground forces were deployed across the Installation, working in conjunction with 001 Anguished Deliberation's sentinels to launch counteroffensives against the S'southi. The S'southi, initially, suffered large casualties from the initial shock of the arrival of Alliance forces in large numbers, though they eventually were able to re-organise their forces and counter the new threat.
=== Race for the Index ===
Despite the S'southi not knowing the location of the Activation Index, they had been searching for it for far longer. Knowing it was only a matter of time until the S'southi located their target, the Galactic Alliance began to deploy teams directly to the location of the Activation Index.
S'southi reconnaissance units would report the large, suspicious movement of troops. Initially believing the Alliance was preparing an army to attack the S'southi, they would begin to follow Alliance forces to the location of the Index. 
Upon the arrival of both forces, they would engage eachother, with large numbers of Sentinels in the area joining to assist the Alliance. Ultimately, the S'southi were defeated and the Alliance secured the Index and managed to get it off-world, though they took heavy casualties in the process.
=== Open Warfare ===
Across the Installation, both armies began to clash in open battles. The Galactic Alliance, despite being outnumbered by the S'southi, had the support of hundreds of thousands of Sentinels which significantly hindered the S'southi's ability to fight. As the Alliance was mainly on the offensive, it took relatively heavy casualties, though the S'southi on average took far more.
By the 17th of December, the majority of S'southi forces had been defeated and Sark had fled from the Ring. The battle would officially end by late afternoon, and the Alliance would station a garrison on the Ring and leave the following day.
== Aftermath ==
The victory at Installation 01 caused 001 Anguished Deliberation to recognise the threat posed by the S'southi. Anguished Deliberation would begin to assist the Alliance in locating a specialized Luminary believed to house the coordinates for the Great Archive.