The Jovian Moons Campaign was a brief conflict in 2160 between the corporate-backed Friedens and the neo-communist Koslovics on several of the Jovian moons, spurred by a Frieden attack on a team of colonial advisers sent by the United Nations to help police the often violent region.
The Spartan II program, led by Dr. Catherine Halsey, was a plan by the Office of Naval Intelligence to use children with superior genetic traits to create a group of super-soldiers in order to put an end to the ongoing Insurrection in the outer colonies.
On their first mission as fully augmented Spartan-IIs, Blue Team, consisting of John-117, Samuel-034, Linda-058, Kelly-087, and Fred-104, infiltrate Eridanus Secundus, a hidden United Rebel Front base located in an asteroid field, and capture Colonel Watts.
The Second Battle of Harvest, also known as just simply the Battle of Harvest, was humanities first attempt to recover the planet Harvest from the Covenant, who wiped out the existing colony and killed tens of thousands of civilians a year earlier.
In an effort to limit the ability for the Covenant to discover human colonies, including the inner colonies and Earth, the Cole Protocol was established to wipe all ship navigation data when the UNSC came into contact with any Covenant forces.
Operation: RED FLAG was a planned operation by both the Office of Naval Intelligence and the UNSC to use Spartans to capture a Covenant ship, use it to penetrate into Covenant space, and capture a Hierarch, with the intent of using the Prophet to broker a cease-fire.
Operation: FIRST STRIKE was a mission undertaken by John-117 and several other Spartan-IIs to infiltrate and destroy the Covenant space station Unyielding Hierophant and associated armada of over 500 warships in the Tau Ceti system prior to the Covenant's invasion of Earth.
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.
At the start of the Covenant in 851 BCE, a group of Sangheili who did not agree with the peace being formed with the San'Shyuum, formed around their leader Ussa 'Xellus and escaped to a previously unknown Forerunner construct known as Shield World 0673.
The Blooding Years is the Sangheili term for the civil war that raged for five years on Sanghelios and throughout Sangheili-occupied territories following the end of the Human-Covenant War and disappearance of the San’Shyuum.
Operation: JOVIAN WHISTLE was an operation executed by the UNSC 717th Xeno-Materials Exploitation Battalion to recover a Forerunner ancilla on the human colony world of Gao in the Cordoba system in the early summer 2553.
The Battle of the Prototype Halo Installation was a conflict between Tem'Bhetek, the former Covenant Minister of Preparation Boru'a'Neem, and the Shadow of Intent crew including Rtas 'Vadum and Tul 'Juran.
Operation: RETRIBUTION was an Office of Naval Intelligence mission headed by operative Veta Lopis and her Ferret team to investigate the murder of Vice Admiral Graselyn Tuwa and the kidnapping of her family members on December 6th, 2553.
The Return to Installation 00 was an Office of Naval Intelligence mission undertaken by the UNSC Rubicon to return to the Ark following the Battle of Installation 00 and investigate the status of the facility in August 2554.
Sometime in January 2557, Rion Forge, a post-war salvager, and her ship the Ace of Spades, discover the location of what was left of the Etran Harborage after the destruction of the shield world during the events of the Battle of the Etran Harborage in 2531.
Following discovery of the last known location of the UNSC Spirit of Fire from the Battle of the Etran Harborage, the Office of Naval Intelligence sent the UNSC Taurokado to investigate the system for any information regarding the whereabouts of the lost UNSC warship.
The Battle of Requiem was a conflict between former Covenant forces under the command of Jul 'Mdama, UNSC forces from the UNSC Infinity and Forward unto Dawn, and Promethean forces under command of the Ur-Didact on Forerunner Shield World 0001, also known as Requiem, in July 2557.
The Battle of New Phoenix was a military engagement between the UNSC and Covenant remnant forces under command of Jul 'Mdama in the city of New Phoenix on Earth, immediately after the New Phoenix Incident and the Battle of Installation 03 in July 2557.
The Assassination of Avu Med 'Telcam was an assassination sanctioned by the Office of Naval Intelligence Section Three and carried out by SPARTAN-G059 on the leader of the Servants of the Abiding Truth on former colony world New Llanelli in the Brunel system in January 2558.
The Battle of Kamchatka was a battle between Covenant remnant forces under the leadership of Jul 'Mdama, local Promethean forces under control of Cortana, and the UNSC in the form of Spartan-IV Fireteam Osiris on the planet of Kamchatka in October 2558.
The Battle of Nuusra was a battle between the remnants of Jul 'Mdama's Covenant forces, the Swords of Sanghelios, and Spartan-IV Fireteam Osiris in the sate of Nuusra on the continent Qivro on the Sangheili homeworld of Sanghelios on October 27th, 2558.
The Battle of Sunaion was a battle between the Swords of Sanghelios led by Thel 'Vadam, their allies Fireteam Osiris led by Jameson Locke, the last of Jul 'Mdama's Covenant forces, and the Created forces led by the Warden Eternal in the state of Sunaion on the Sangheili homeworld of Sanghelios.
Sometime long before the time of the Forerunners, the Precursors created the Domain, a repository of all knowledge in the universe. The exact date is unknown, and while some sources say it was created 500 million years ago, others say it has existed for billions of years.
~107,445 BCE - 106,445 BCE
After the emergence of the Flood on ancient human worlds around 107,445 BCE, human civilization was desperate to expand their territory away from Flood-controlled regions of space. As part of this expansion, humans clashed with Forerunner-populated worlds, sparking a war between the two species.
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.
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.
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.
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.
Following the Didact’s self-imposed exile one thousand years prior after losing the political battle over the Forerunner defense plan against the Flood, the Didact is resurrected from his cryptum on Erde-Tyrene by Forerunner Manipular Bornstellar Makes Eternal Lasting, and humans Chakas and Riser.
After the Revival of the Didact and his exploration of the Charum Hakkor system with fellow Forerunner Bornstellar Makes Eternal Lasting and humans Riser and Chakas, the Didact and crew traveled to the quarantined San’shyuum homeworld of Janjur Qom to try and unlock more memories in their quest for understanding.
In the aftermath of the Fate of Maethrillian and destruction of the Forerunner ecumene, Zeta Halo implemented it’s security measure designed to prevent the ring from falling into enemy hands and performed a slipspace jump into another system and put itself on a collision course with a nearby planet.
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.
Over one-hundred years after the Great Purification, the few Forerunners remaining on the Lesser Ark became aware that the firing of the Halo Array may have had a detrimental effect on the Domain, and proceeded to the former Forerunner capital of Maethrillian to attempt to restore it.
2200 BCE - 2100 BCE
The War of Wills was a fierce and prolonged conflict between two factions of the San’Shyuum: The Stoics who wanted to worship Forerunner technology but never use it, and the Reformists who wanted to take advantage of the incredible Forerunner artifacts around the galaxy.