A timeline of all major events in the Halo universe from the time of the Forerunners through the rule of the Created.
The Battle of the Etran Harborage was a battle between the UNSC Spirit of Fire and Covenant forces lead by Arbiter Ripa 'Moramee on Shield World 0459, also known as the Etran Harborage.
The Battle of Installation 04 was an engagement between the UNSC Pillar of Autumn and the Covenant Fleet of Particular Justice on and around the Forerunner megastructure known as Installation 04, or Alpha Halo, in the Soell system.
The Battle for Earth was a large-scale space, air, and ground battle between the invading Covenant forces and the UNSC Home Fleet on and around Earth at the end of 2552.
The Skirmish on Mona Lisa was a minor conflict that occurred in the debris field of Installation 04 in the Soell system aboard the prison ship Mona Lisa between UNSC forces and an outbreak of the Flood on October 25th, 2552.
The Battle of Installation 05 was an engagement between the Covenant forces, including those that fled the Battle for Earth, High Charity, and the Second Fleet of Homogeneous Clarity, and the UNSC-allied forces, including the UNSC In Amber Clad led by Miranda Keyes, and the Fleet of Retribution led by the Arbiter Thel 'Vadam.
The Battle of Installation 00 was a major conflict between the forces stationed aboard the UNSC Forward Unto Dawn and Arbiter Thel 'Vadam's Fleet of Retribution, and the Covenant fleet loyal to the Prophet of Truth.
The Second Ark Conflict was a battle between the UNSC forces aboard the Spirit of Fire and the Banished forces under command of Atriox on Installation 00 in 2559.
The Outbreak on Installation 00 was a brief encounter between Banished forces and the Flood on the surface of the Ark in and around the wreckage of the Covenant holy city High Charity.
~107,445 BCE
The birth of the Flood is actually a series of events that can be traced to a time period around 10,000 years prior to the firing of the Halo Array in 97,445 BCE.
~106,538 BCE
Sometime prior to the end of the Human-Forerunner Wars, ancient humans discovered a Precursor stasis chamber containing a creature they called the Primordial. The creature, along with the stasis chamber, was taken to Charum Hakkor where is was interrogated, teaching the humans on the origins of the Flood.
~97,745 BCE
Around 97,745 BCE, nearly nine-thousand years since the Flood disappeared from the galaxy during the Human-Forerunner Wars and three-hundred years before the Great Purification, the Flood were first observed at the edges of the galaxy on the planet Seaward, a Forerunner colony world.
~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.
~97,495 BCE
The release of the Primordial was an unintended consequence of the test-firing of a Senescent Halo, Installation 07, by the Master Builder and Mendicant Bias in the Charum Hakkor system during the Forerunner-Flood War, approximately fifty years prior to the end of the war and the Great Purification.
~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 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.
