The Great War

The Great War, a name often applied to the Human-Covenant War, covers historical events during that conflict from 2525 up to its conclusion in 2552. As the war marked the intersection of the two civilizations' timelines, both human and Covenant-related events are listed; for prior events, Human history and Covenant history should be used. The Great War is followed by the Reconciliation Era, beginning in 2553.

To view all of the era pages, see Timeline.

2520s
The 2520s saw the beginning of the war, with the Covenant making massive advancements into human territory at a frantic pace in the first three years. Despite the UNSC's attempts to tie the Covenant down at Harvest, along with the successful counterattack of Operation: SILENT STORM, large swathes of colonies in FLEETCOM Sector 2 had been glassed by the end of the decade.

2525

 * May 14: The Ascension ceremony of the High Prophets of Truth, Mercy and Regret, the formal beginning of the Ninth Age of Reclamation, and the announcement of the holy war against humanity to the Covenant masses.

2530s
In the 2530s, the main front of the war gradually shifted to FLEETCOM Sector 1 as new invasion routes were opened in the Orion-Eridanus region, though with the destruction of the K7-49 shipbuilding plant the front eventually died off, sparing some of the inner Orion-side colonies; without Operation: PROMETHEUS, Reach (and even Earth) may have been discovered over a decade earlier.

2534

 * The enters service.

2537

 * The and  enter service.

2540s
The early to mid 2540s were marked by a decreasing operational tempo. There were fewer attacks, and the Covenant fleets were smaller. There was a hope on the UNSC side that the Covenant had exhausted their supply routes, or were possibly suffering from war fatigue. It was even thought that the battle of Psi Serpentis broke the Covenant's back. The Pleiades Corridor invasion route, which had been established in the late 2530s, began the Covenant's incursion into Sector 4, though battles also continued elsewhere, namely the inner Scorpius front in Sector 2. The refinery at Pegasi Delta was constructed soon after to push deeper into human territory, though its destruction in Operation: TORPEDO saw the end of the concerted push into the Sector 3 Outer Colonies in the Aquila-Sagittarius side and the redirection of the Covenant's attention toward the Inner Colonies. Against the UNSC's hopes, the Covenant's pace picked up in the later half of the decade, continuing up until late 2552.

2543

 * The enters service.

2547

 * The enters service.

September

 * The first contingent of the SPARTAN-III Gamma Company is deployed into combat.

October

 * October 20
 * The Battle for Earth begins as the Prophet of Regret's Fleet of Sacred Consecration enters the Sol system.


 * Using data from a Forerunner Wayfinder, the Prophet of Regret jumps towards Halo Installation 05 aboard his flagship, the Solemn Penance. By this point, most of Regret's forces on Earth have been crushed due to their insufficient numbers and unpreparedness against the military might of humanity's homeworld.


 * With navigation data transmitted by Regret, High Charity and much of the holy city's retinue follows suit several hours later from their position in the Soell system.

November

 * November 2
 * The Solemn Penance arrives at Installation 05, with the In Amber Clad following in its wake. Regret's troops land on the ring, with the Hierarch himself establishing himself in a Forerunner temple. Several hours later, Regret is assassinated by the Master Chief. Even before Regret's death has been confirmed, the Prophet of Truth orders the shipmaster of the Solemn Penance to fire upon the temple in order to kill the "Demon".


 * Citing Regret's death as proof of the Sangheili's incompetence at protecting the Hierarchs, the Prophet of Truth orders the Changing of the Guard; the first step of the replacement of the Sangheili.


 * November 3
 * The Great Schism begins.


 * The UNSC prowler Dusk arrives at Installation 05 on the In Amber Clad's tail to witness the Covenant ships turning on one another.


 * The Flood infiltrates High Charity and spreads throughout the surface of Delta Halo.


 * The Prophet of Truth flees High Charity aboard the Forerunner Dreadnought, uncoupling the ancient keyship from High Charity's power grid for the first and last time. Unknown to Truth, the Master Chief has stowed away aboard the ship as it heads for Earth.


 * Most of the Sangheili High Councilors are ambushed and killed by the Jiralhanae while gathering for the consecration ceremony of the Sacred Icon in Delta Halo's control room.


 * On the surface of Installation 05, the Arbiter leads fellow Sangheili, Unggoy and Mgalekgolo in an uprising against the Jiralhanae, liberating several surviving Sangheili Councilors in the process. With the help of fellow Schismatics and Sergeant Major Avery Johnson, the Arbiter carves a path through Covenant loyalist resistance into Delta Halo's control room. The Arbiter confronts and kills Tartarus, while Commander Miranda Keyes stops the ring from firing at the last moment.


 * Following Tartarus' defeat, Schismatic forces led by Rtas 'Vadum capture the Jiralhanae-held cruiser Pious Inquisitor, holding position near the control room. Soon after, 'Vadum assumes command of the Sangheili-held Shadow of Intent, while the Arbiter, Keyes, and Johnson depart for Earth aboard the Pious Inquisitor.


 * Imperial Admiral Xytan Jar 'Wattinree summons prominent Sangheili leaders to Joyous Exultation in response to the Schism; the message reaches most factions within a day or two.


 * A few hours into the Schism, the cruiser Incorruptible under the command of Voro 'Mantakree departs Delta Halo for Xytan Jar 'Wattinree's summit at Joyous Exultation.


 * Most of the remaining Schismatics at Delta Halo organize their forces under the Fleet of Retribution. The Sangheili fleet establishes a quarantine around the Halo ring.


 * November 4
 * Now stranded on High Charity, Cortana begins broadcasting an emergency message to Earth, declaring hazard codes BANDERSNATCH and HYDRA, as well as recommending the UNSC to NOVA bomb Delta Halo.


 * November 7
 * Roused by the priming of the Halo Array, the local Sentinels on Onyx begin attacking the UNSC forces at Camp Currahee, effectively stranding them with the destruction of the UNSC Agincourt in orbit. By this point, only three Gamma Company teams remain on Onyx to compete for top honors; during the initial Sentinel attack, Team Gladius is wiped out by the Sentinels while Team Katana disappears into Zone 67, leaving only Team Saber, the Beta Company Spartans Lucy-B091, Tom-B292, SCPO Mendez and LCDR Ambrose, with most of Camp Currahee's other personnel slaughtered in the attack. SCPO Mendez declares emergency code BLOODY ARROW on the UNSC E-Band.


 * November 8
 * The Prophet of Truth's Keyship arrives in the Sol system. While Truth's forces finish the excavation, soften up UNSC defenses, and secure the portal site, the Forerunner ship loops around Sol in a long elliptical orbit. The Master Chief attempts to unsuccessfully kill the Prophet, and is eventually trapped in a sealed section of the ship for several days.


 * November 11
 * The Dusk returns to Sol following the Forerunner Dreadnought's slipspace wake.


 * November 12
 * Dr. Halsey and Kelly-087 arrive at Onyx aboard the stolen insurrectionist vessel Beatrice. They link up with the UNSC survivors at Camp Currahee and Halsey uses Cortana's emergency transmission, broadcast through the Covenant's wavecaster network, as a carrier wave for her own message to Earth, in which she requests that HIGHCOM send Spartans to procure strategic Forerunner technology from Onyx.


 * November 13
 * Aboard his flagship Sublime Transcendence orbiting the base-world Joyous Exultation, Xytan Jar 'Wattinree opens his summit with the Sangheili leaders who heeded his summons. The Imperial Admiral declares the creation of a new Covenant as well as his plans to deal with the Jiralhanae alpha-tribes through luring them into an ambush under the false pretense of a parley. Having intercepted Dr. Halsey's transmission, 'Wattinree has now-Fleetmaster Voro Nar 'Mantakree assigned to retrieve Forerunner relics from Onyx and prevent them from falling into human hands, while his own forces prepare for their trap against the Jiralhanae. Mere moments after 'Mantakree's fleet departs for Onyx, a NOVA bomb transported from Reach is accidentally triggered by Huragok aboard the Sublime Transcendence, atomizing the Imperial Admiral along with most of his followers, destroying a large portion of his fleet, and razing the surface of Joyous Exultation.


 * On Earth, Blue Team secures the Centennial Orbital Elevator in Havana. As they ascend the elevator, Fleet Admiral Terrence Hood receives Dr. Halsey's request for aid from Onyx. Blue Team captures the Covenant destroyer Bloodied Spirit and heads for Onyx, with the intent of capturing Forerunner technology. Lord Hood assigns Admiral Patterson's Battle Group Omicron to follow the Bloodied Spirit to assist the Spartans in their mission.


 * November 14
 * Blue Team arrives at Onyx aboard the Bloodied Spirit and soon link up with the UNSC survivors. Battle Group Omicron, including the prowler Dusk, follows in their wake. However, Voro Nar 'Mantakree's task force arrives at Onyx and engages the UNSC battle group, while the Spartans, Dr. Halsey and SCPO Mendez push further into the restricted Zone 67 and finally the bowels of Onyx itself. Pursued by 'Mantakree's forces to Onyx's core, the Spartans make a final stand around a slipspace portal with an uncertain destination. Lieutenant Commander Kurt Ambrose sacrifices himself to hold off the Covenant, detonating two FENRIS nuclear warheads to seal the entrance and eradicating the Covenant forces. As the portal closes, Onyx's surface unravels itself, revealing a foundational lattice composed of trillions of Sentinels making up the entire planet. The Sentinels form a defensive perimeter around the planet's heavily fortified core, obliterating 'Mantakree's fleet and prompting the Dusk to retreat back to Earth.


 * November 15
 * Now inside a Forerunner Dyson shell encased in a slipspace bubble in what was once Onyx, the survivors of the battle hold a memorial service for their fallen comrades. Immediately afterward, they move out to find a way outside the shield world and back to the UNSC.


 * The Arbiter, SgtMaj Johnson and Commander Keyes arrive at Earth aboard the Pious Inquisitor.


 * At Joyous Exultation, the Jiralhanae fleets summoned to parley there defeat the Sangheili stragglers, thrown to disarray by the detonation of the NOVA bomb. Now in control of the system, the Jiralhanae warpacks spread throughout the Oarthen Threshold and nearby domains. The few Schismatic survivors in the Salia system are forced into a bitter retreat.


 * November 16
 * The Prophet of Truth commits all his ships into a final offensive in Earth's orbit, crushing what remains of UNSC opposition and launching devastating surface bombardments.


 * Truth sends a final summons to all of his loyalists to gather at Earth for the passage to the Ark, with the warning that those who do not make it in time will be left behind. Many do not make it, and others are too busy raiding, pillaging or fighting the Sangheili to even bother trying.


 * November 17
 * With the Home Fleet smashed and the artifact nearly uncovered, the Forerunner Dreadnought enters Earth's atmosphere in the early hours of November 17, landing in the center of the Voi Excession. John-117 ejects from the ship using an airlock door as a heat shield upon re-entry. Making a rough landing in the East African jungles near Mount Kilimanjaro, he is tracked down and recovered the next morning.


 * The main contingent of the Fleet of Retribution, commanded by Rtas 'Vadum, arrives at Earth.


 * Truth's fleet departs for the Ark, followed by the Fleet of Retribution.

December

 * December 11-13
 * The Battle of the Ark takes place.