97,445 BCE

In approximately 100,000 BCE, the Forerunner-Flood war came to a close.

• The Librarian visits the San 'Shyuum homeworld Janjur Qom to collect specimens in order to protect the San 'Shyuum species from the Flood at the Ark. This sparks unrest among the San 'Shyuum population, who soon begin a rebellion against the Forerunners.

• The Didact is resuscitated from his exile in a Cryptum by Bornstellar Makes Eternal Lasting. They later make their way to Janjur Qom, where the Didact is interrogated and eventually executed by the Master Builder, but lives on in Bornstellar's body through an imprint acquired in his mutation. Shortly afterward, the Master Builder authorizes the use of a Halo ring to put down the San 'Shyuum rebellion by sterilizing the entire system. For this, the Master Builder is placed on trial and the Forerunner Council decides that the Halo rings be decommissioned.

• The Forerunner AI known as Mendicant Bias, having been seduced by Gravemind and descended into rampancy, returns from his 43-year absence with one of the Halo rings and launches an assault on the Forerunner capital, presumably crippling the Forerunner government. The Didact, having survived the battle, assumes command of Forerunner military forces after a thousand years of exile.

• In the final hours of the war, the Forerunners realize that activating their last resort, the Halo Array, is the only way to stop the Flood from overrunning the galaxy. As the Didact prepares to activate the rings, Mendicant Bias assembles all Flood-controlled vessels into a fleet of 4.8 million ships, and breaches the Maginot Sphere. On the other side awaits Offensive Bias and its combined fleet. As the two fleets engage each other, the Halo Array is fired. The Halo pulse kills all sentient life within three radii of the galactic center, including any Forerunners not located on The Ark or within Shield Worlds. Minutes after the firing of the array, Mendicant Bias's fleet is decimated by Offensive Bias.

• Some time after every sentient species, carefully indexed in the Ark, is returned to their homeworlds as a part of the Library Project, the Homo sapiens species begins migrating out of Africa.

Trivia

343 Guilty Spark put the date of the firing of the Array as the year 97,448 BCE, though it should be noted that he measured it on Installation 04's year, not the 365.25 day Earth calendar.