~98,395 BCE

The end of the Human-Forerunner War, along with the political fight afterwards that led to the Exile of the Didact, spurred much debate within Forerunner leadership about the right course of action to defend civilization and the galaxy against the Flood, should they return.

~97,745 BCE - 97,445 BCE

The Forerunner-Flood War was a military engagement between the Forerunner species and the Flood that took place over approximately three-hundred years from 97,745 BCE until 97,445 BCE.

~97,450 BCE

After the Master Builder captured the Didact over Janjur Qom, he decided to dispose of the Didact on a derelict Forerunner ship with a handful of other political prisoners in an area of Flood-controlled space known as a Burn.

~97,445 BCE

The Battle of the Greater Ark was one of the final battles of the Forerunner-Flood War and saw the decimation of almost all remaining Forerunner forces just prior to the firing of the Halo Array during the Great Purification in 97,445 BCE.

~97,445 BCE

The behavior of the Ur-Didact following his encounter with a Gravemind and return to the Forerunner civilization became more erratic and harder for the IsoDidact and Librarian to cope with as the Forerunner-Flood War continued.

~97,445 BCE

The Great Purification was the final event of the Forerunner-Flood War, purging the entire Milky Way galaxy of all sentient life, including Forerunners, the Flood, and any other species that may have survived the Flood infestation.