2552

2552 was the penultimate year in the Human-Covenant War, during which the humans of the United Nations Space Command nearly saw utter defeat and extinction, though the tide turned, and with the help of the Sangheili, won the Human-Covenant War. The Covenant were at the peak of their power and reach in 2552, with major assaults on the Human Inner Colonies and an invasion followed by a prolonged engagement on their home planet, Earth. During the battle at Installation 04, the galaxy found its first large outbreak of the Flood threat in over a hundred thousand years. Over two months later, an even larger outbreak occurred at Installation 05.

The war finally drew to a close at Installation 00, known more commonly as the "Ark", with the humans and Sangheili attempting to assassinate the Prophet of Truth, before he could activate the remaining Halo Installations. The alliance was successful in their mission against the Covenant.

January
January 8
 * A team of ODST's (Including Kojo Agu and Taylor H. Miles) descend onto Ariel (a small science colony) in response to a distress call on the planet in Operation: FIRESIDE.

February

 * Insurrectionists on Harmony disable the planet's primary communications relay and steal two drydocked freighters.

April
April 22
 * Battle of Fumirole: Noble Team member Thom-293 destroys a CCS-class battlecruiser but kills himself in the process, and Catherine-B320 loses her arm. She subsequently receives a robotic prosthetic.

May
May 10
 * SPARTAN-B312 takes place on a counter-insurgency operation on Mamore. The SPARTAN's skills as a Sabre pilot are exhibited during the op, prompting Colonel Urband Holland to have the SPARTAN transferred to Noble Team.

July
July 17
 * The Slipspace probes from the Archimedes encounter the Covenant ships sent to attack Sigma Octanus IV
 * The is tasked with patrolling the Sigma Octanus Star System.
 * The Battle of Sigma Octanus IV begins.

July 18
 * The UNSC win a victory during the battle at Sigma Octanus IV. Commander Jacob Keyes, of the, plays a critical role in this success when he devises the Keyes Loop. Keyes is subsequently promoted to Captain by Vice Admiral Michael Stanforth. Unknown to the UNSC, the Covenant place a tracker on the hull of the Iroquois. The importance of Reach to the UNSC is revealed to the Covenant when the Iroquois returns to that world.
 * Michael Stanforth messages the director of the Office of Naval Intelligence, Margaret Orlenda Parangosky, with information on the Sigma Octanus IV event, as well as the ongoing progress of Operation: BRAVADO.

July 24
 * Two months after the death of Thom-293, SPARTAN-B312 joins Noble Team as Noble Six.
 * Noble Team is sent by Colonel Urban Holland on a mission to investigate a downed communication relay on Reach.
 * The Covenant begin their invasion of Reach.
 * Noble Team discovers the Covenant's presence on Reach for the first time, learning that it was they who sabotaged the relay at Visegrad. Planetary directive WINTER CONTINGENCY is declared.

July 26
 * Sword Base, a ONI research facility comes under attack by a Covenant corvette. The UNSC Army with the help of Noble Team successfully repel the attack and the corvette is destroyed by orbital support.

August
Unknown date
 * After discovering Reach, the Covenant move on to glass the other planets in the system, including Tribute, resulting in the prolonged Battle of Tribute.
 * During the Battle of Tribute, SPARTAN-II Team Black is sent to Verge to destroy a Covenant Beacon supplying helium-3 to the ships laying siege on Tribute. The team successfully destroys the beacon.
 * After the mission on Verge, Fireteam Black is assigned to Operation: BLOWBACK, a covert mission in Covenant-occupied space. Their ship, as well as a Covenant carrier, crash-land on an unknown moon, igniting the Battle of Line Installation 1-4.

Early August (sometime from the 6th to the 12th)
 * The crashes in lunar orbit, a Slipspace Anomaly knocking out communications within the Solar System for seven seconds.

August 12
 * John-117 and Corporal Harland are debriefed by ONI at Camp Hathcock, Reach, on the events on Côte d'Azur during the Battle of Sigma Octanus IV.
 * Battle of Viery: UNSC forces assault an amassing Covenant invasion force in the Viery Territory on Reach, managing to destroy two AA plasma cannons and a Covenant spire. However, a cloaked Covenant supercarrier (the Long Night of Solace) that spearheaded the Covenant invasion is revealed; the supercarrier destroys the frigate, which had been providing air support.

August 13
 * 60% of the remainder of the UNSC fleet is recalled to Reach, destined to arrive within the next 48 hours.

August 14
 * Operation: UPPER CUT is initiated, as Noble Team retakes the Sabre Program Launch/Research Range and joins the battle in orbit, eventually capturing the Covenant corvette Ardent Prayer and using it to deliver the 's Shaw-Fujikawa Translight Engine, used as a makeshift bomb, to the Long Night of Solace . The Solace is destroyed at the cost of Jorge-052, who sacrifices himself to detonate the drive manually. Moments after the carrier's destruction, a large Covenant fleet enters in-system.

August 18
 * The Siege of New Alexandria begins as the Covenant lay siege to the city of New Alexandria.

August 23
 * Noble Six arrives in New Alexandria and rescues civilians by helping them escape. Noble Six eventually meets up with the rest of Noble Team, and the Covenant begin glassing the city. As Noble Team is on their way to a fallout shelter under the Olympic Tower, Catherine-B320 is killed by sniper fire.

August 25
 * Dr. Halsey and Cortana choose the, with Jacob Keyes as its commander, for a secret mission Halsey is planning.

August 26
 * The remainder of Noble Team is evacuated from the destroyed New Alexandria via a Pelican.

August 27
 * All available SPARTAN-IIs gather at the FLEETCOM Military Complex on Reach, where they learn of their next mission: to acquire a Covenant vessel, navigate to the Covenant home world, and return with captured Covenant leadership.

August 29
 * John-117 receives a neural interface upgrade, MJOLNIR Mark V armor, and is introduced to Cortana.
 * Noble Team is ordered to destroy Sword Base in a torch-and-burn op. During the operation, Noble Team makes their way inside Sword Base where they encounter Dr. Halsey, who asks them to protect her lab. Noble Team is then given direct orders to escort a fragment of Cortana holding crucial data from the Babd Catha Forerunner Complex to the Pillar of Autumn. Halsey is then escorted back to CASTLE base by Jun-A266.

August 30
 * Cortana has ONI Colonel James Ackerson illicitly transferred to the front. This is her revenge for his attempts to eliminate both her and SPARTAN-117.
 * First Lieutenant Jake Chapman, along with most of Charlie Company is killed during the Fall of Reach.
 * The Covenant, despite sustaining heavy losses, wins a crushing victory at the Fall of Reach. Many of the remaining SPARTAN-IIs are killed.
 * The surviving SPARTAN-IIs on Reach are separated into two groups. One recovers Vice Admiral Whitcomb and goes into hiding at Camp Independence. The others are admitted into CASTLE Base by Dr. Halsey and receive parts of the MJOLNIR Mark V upgrade and new weapons.
 * Dr. Halsey learns of Colonel Ackerson's mysterious plans that seem to involve "her" Spartans.
 * SPARTAN-B312 destroys a CCS-class battlecruiser with a mass driver to allow the Pillar of Autumn to escape Reach. The Spartan is killed by Sangheili soon after. The Autumn jumps away from the system, with Cortana using Forerunner navigation data from the Sigma Octanus IV Artifact as well as the Babd Catha Forerunner complex.

September

 * The planet Coral is reported glassed by the Covenant.
 * The Battle of New Jerusalem takes place. After a chain of events involving a group of ODSTs attempting to steal gold from a bank vault, the 26th Marine Expeditionary Force is nearly wiped out, leaving the Rookie as one of few survivors. Eventually, the UNSC forces cut their losses and fall back to Earth.

September 4
 * Lieutenant Wagner returns to Earth and reports on the evident destruction of Reach to Colonel James Ackerson, Admiral Hood, and Major General Strauss at HIGHCOM Facility Bravo-6 in Sydney, Australia.

September 14
 * Earth's Orbital Defense Platforms are scheduled to come online.

September 19
 * The arrives at Alpha Halo.
 * The Battle of Installation 04 begins.
 * SPARTAN-117 is awoken from cryo sleep and tasked with preventing Cortana's capture by the Covenant.
 * SPARTAN-117 and Cortana escaped the ship aboard a Bumblebee-class Lifepod, which later crashed on the ring.
 * The is forced to crash land on the ring. A significant portion of its crew survives to continue the fight on the ground.


 * Captain Keyes and the others in his escape pod are captured by the Covenant. Only Keyes escapes summary execution, and is taken to the Truth and Reconciliation.
 * SPARTAN-117 leads a Marine force to board the Truth and Reconciliation. They recover Keyes and escape aboard a Covenant dropship.

September 20


 * Keyes orders SPARTAN-117 to find the "Silent Cartographer", a map room that will reveal the location of the Control Room. Keyes leaves to lead an assault on a Covenant weapons cache.
 * Having found the map room and the pertinent information, Cortana directs a Pelican to take them to the area where the ring's Control Room is. Upon reaching the Control Room, Cortana transfers to the Control Room's computer and directs SPARTAN-117 to stop Keyes from accessing the 'weapons cache', really a Forerunner research and quarantine facility.
 * SPARTAN-117, without Cortana, enters the facility but is unable to locate Keyes. Instead, he discovers the "Flood" and is forced to retreat. He links up with marines and takes command of the surviving members of Keyes' team and together they fight their way to the extraction point. However, the Spartan is conscripted by the "Monitor of Installation 04" and teleported away before he can be evacuated with the surviving members.

September 21
 * The Monitor takes John-117 to the ring's "Library" to retrieve the "Index", a device needed to activate the ring's primary weapon. Having retrieved the Index, the Monitor teleports the Spartan back to the Control Room where an irate Cortana confiscates the Index and prevents the ring from firing. SPARTAN-117 and Cortana flee a now-hostile 343 Guilty Spark and Sentinels.
 * To forestall the ring from being activated manually, SPARTAN-117 disables the ring's three Pulse Generators. This is to buy time to destroy the ring by activating the auto-destruct on the . Only Keyes neural interface can activate the ship's self-destruct, and SPARTAN-117 embarks once more to rescue the captain.
 * Cortana teleports the Spartan to the Flood-overrun Covenant cruiser where Jacob Keyes is being held. Alas, the pair arrives too late to save Keyes, who has been merged into a Brain Form. SPARTAN-117 retrieves the neural interface by punching in the former-captain's head. Cortana downloads the necessary codes, and the duo returns to the on a captured Banshee.

September 22
 * 343 Guilty Spark overrides the auto-destruct sequence, forcing SPARTAN-117 to manually destabilize the ship's still-functioning fusion cores. SPARTAN-117 and Cortana then escape the resulting explosion and the fragmentation of the ring aboard a Longsword.
 * Staff Sergeant Johnson, Lieutenant Haverson, Warrant Officer Polaski, Corporal Locklear also escape the destruction of the ring aboard a Pelican.
 * SPARTAN-117 and Cortana rendezvous with Johnson's group in Installation 04's debris field. They also recover a set of cryo chambers, one which contains SPARTAN-058.
 * The Battle of Installation 04 ends. Gunnery Sergeant Stacker and PFC Chips Dubbo survive, but it is unknown how they do.
 * Skirmish over Threshold: As the Longsword and Pelican are not jump capable, the UNSC survivors assault and capture the Ascendant Justice, a Covenant warship and apparently the flagship of the Covenant Fleet sent to Installation 04. They then set course for Reach.
 * Jersey Morelli confronts his mother about having an affair.

September 23
 * A Time/Date Record Anomaly continues from this point in the narrative, resolved above on Sep 7, 2552.

September's Anomaly
After the recovery of a Forerunner device on Reach, the members of an organized resistance comprised of SPARTANs from Reach and survivors of the Battle of Installation 04 are in some sort of time anomaly, causing them not to be in the "correct timeline". What is known is that the events taken place with the possession of the device take place after September 7.

September 7
 * The Time/Date Record Anomaly of Sept 23, 2552 most likely rejoins the correct timeline.
 * Dr. Halsey and members of Red Team discover an enigmatic shard in a Forerunner installation below CASTLE Base. They are besieged by Covenant forces who seek to possess the shard.
 * Dr. Halsey initiates Operation: WHITE GLOVE, destroying CASTLE Base, thus preventing the Covenant forces above from capturing any UNSC or Forerunner technology. Halsey and members of Red Team are protected from the resulting detonation when they hide in the caves beneath the base.
 * The remaining Spartans, Admiral Whitcomb, Dr. Halsey, Sgt. Johnson, Lieutenant Haverson, Warrant Officer Polaski, and Corporal Locklear jump to Slipspace on board the Covenant/Human hybrid ship -Ascendant Justice'', and discover that the shard seems to have the ability to bend both space and time.

September 12
 * The Gettysburg/Ascendant Justice arrives for refit and provisioning in Eridanus system and meets with the rebels under Governor Jiles. Dr. Halsey sedates Spartan 087, Kelly, and absconds with her on Governor Jiles' personal ship, the Beatrice. Before she goes, she gives the alien artifact to Corporal Locklear, with implicit instructions to destroy it.

September 13
 * UNSC forces aboard the Gettysburg/Ascendant Justice win a crucial victory at the Battle of the Unyielding Hierophant. SPARTAN-093, Lieutenant Haverson of ONI and Vice Admiral Whitcomb are killed. The survivors, now aboard the singular and with a captured Covenant slipspace drive, depart for Earth to warn of the impending Covenant invasion.

October
Unknown date
 * An Edict from the Office of the High Prophet of Truth orders that in the virtue of the Jiralhanae, all Sangheili posted with the Fleet of Profound Solitude, the Fleet of Tranquil Composure, and the Fleet of Inner Knowledge to be completely replaced by Jiralhanae. Each removed Sangheili to be assigned other duties. In celebration, all imprisoned or criminal Jiralhanae were released, rehabilitated, and pardoned.
 * Prior to October 20, the is sent to Installation 04's debris field in the Soell system to scout the area for survivors. They detect the prison ship Mona Lisa and deploy Marines into the ship. Soon after, it is revealed that the ship is infested by the Flood and was used by the Office of Naval Intelligence as a laboratory to test the parasite on prisoners. The infestation is contained as the Red Horse unleashes a Shiva-class nuclear missile on the Mona Lisa, destroying it.

October 20
 * SPARTAN-117 is outfitted with the MJOLNIR Mk. VI aboard Cairo Station.
 * Thel 'Vadamee, the Supreme Commander of the Fleet of Particular Justice, is deemed a heretic by the Covenant High Council and is sentenced to death.
 * SPARTAN-117 and Staff Sergeant (now promoted to Sergeant Major) Johnson are decorated at a ceremony aboard Cairo Station. Captain Keyes is awarded posthumously and the decoration is entrusted to Lieutenant Commander Keyes.
 * The Battle of Earth begins.
 * The High Prophet of Regret's fleet arrives at Earth, not expecting any human presence. The vastly outnumbered Covenant force attacks without seeking support from other Covenant forces.
 * SPARTAN-117 foils a Covenant attempt to demolish Cairo Station and commandeers the Covenant bomb to destroy an assault carrier.
 * The High Prophet of Regret's assault carrier, Solemn Penance breaks through the orbital defenses and initiates a ground assault on New Mombasa and the surrounding area.
 * A squad of ODSTs, consisting of Corporal Taylor "Dutch" Miles, Lance Corporal Kojo "Romeo" Agu, PFC Michael "Mickey" Crespo, and The Rookie, led by Captain Veronica Dare and Gunnery Sergeant Edward Buck, launch into New Mombasa from the.
 * SPARTAN-117 deploys to New Mombasa in an attempt to capture the High Prophet of Regret. Before this can happen, the assault carrier initiates a slipspace jump within the city, escaping Earth and severely damaging the city in the process. The, with SPARTAN-117 aboard, successfully pursues the carrier through slipspace.
 * Immediately after Regret's retreat, an additional Jiralhanae-led Covenant occupation force is inserted to New Mombasa, as a part of the Prophet of Truth's plan to eventually replace the Sangheili with the Brutes as the Covenant's primary warrior race. For the rest of the day, UNSC and Covenant forces battle for control of the city. Meanwhile, the Covenant fleet begins the process of uncovering the Ark portal.
 * The ONI Alpha Site in New Mombassa is destroyed by the combined forces of the UNSC and the New Mombasa Police Department, led by Corporal Miles and and PFC Crespo, in order to prevent the Covenant from accessing it. The explosion inadvertantly awakens a large Drone hive in the tunnels below the base.
 * The former Fleet Commander of Particular Justice is made the Arbiter by the High Prophets of Truth and Mercy.
 * The Arbiter destroys a heretic group and 'recovers' the Oracle during the Battle of the Gas Mine.

October 21
 * The Battle of Mombasa ends with a Covenant victory.
 * In the dawn, Covenant reinforcements sent by the Prophet of Truth continue arriving at Earth to uncover the Portal.
 * Buck's ODST squad escapes New Mombasa as the city, along with its surroundings are glassed by the Covenant excavation fleet.

October 20 through November 2
 * The Spartan-II Blue Team is deployed to defend Earth during the two weeks that follow the initial Covenant invasion. They participate in numerous combat missions on and around Earth, including Battle of Ross Island in the Antarctica and an underwater operation in the Yucatan Peninsula.

October 31
 * The Battle of Onyx begins.
 * The standby signal rouse the Sentinels of Onyx, who destroy the UNSC base on the world.
 * SPARTAN-III Gamma Company Team Gladius is totally wiped out by the Sentinels. Team Katana is forced into Zone 67, and Team Saber loses contact with Camp Currahee.
 * Kurt-051, SPCO Franklin Mendez and Petty Officers Tom-B292 and Lucy-B091 begin to form a resistance against the Sentinels.
 * The, in high orbit above Onyx, is destroyed by Sentinels.
 * Chief Mendez declares emergency code Bloody Arrow over the UNSC E-BAND.

November
The end of 2552 saw the bloodiest period of the Great War and the beginning of the end. The Prophet of Truth was killed in the later months along with a sizable Covenant armada, leaving the Covenant forces crippled and leaderless as well as the full destruction of Gravemind and its Flood forces.

November 2
 * The Battle of Installation 05 begins.
 * The UNSC In Amber Clad arrives at Delta Halo, following the High Prophet of Regrets assault carrier. SPARTAN-117, aided by ODSTs and marines, pursue the High Prophet to a Forerunner temple and assassinate him. However, orbital bombardment from the escorting fleets of the newly arrived High Charity destroys the temple. SPARTAN-117 is thrown into a lake and captured by Gravemind.

November 3
 * The Great Schism begins.
 * The arrives at Delta Halo and witnesses the final stages of the Battle of Installation 05. She retreats to Earth via a slipspace wake caused by the Forerunner ship.
 * Dr. Halsey and Kelly-087 arrive at Onyx and are trapped along with the rest of the human survivors. Halsey sends a distress signal piggybacked on Cortana's October 28 signal.
 * The Battle of Havana is fought. Having received Halsey's signal, SPARTAN-043, SPARTAN-058, and SPARTAN-104 redeploy from Earth to Onyx aboard a captured Covenant ship. They rendezvous with Halsey. The UNSC survivors are forced to retreat underground as a newly arrived Covenant fleet begins landing troops.
 * Voro 'Mantakree is promoted to Fleet Master by Imperial Admiral Xytan 'Jar Wattinree, and is given the mission to intercept the SPARTANs heading for Onyx and to retreieve the Forerunner technologies said to be there.
 * Danforth Whitcomb's NOVA bomb detonates onboard the Covenant supercarrier Sublime Transcendence, in orbit above the Sangheili outpost world Joyous Exultation, destroying every ship in the vicinity, and also scorching a quarter of Joyous Exultation and compleatly vaporizing the nearby moon Malhiem.
 * The Dusk arrives at Earth after mere hours. Upon arrival, she is re-assigned to Battlegroup Stalingrad. The group jump to Onyx via the captured Covenant Ships Slipspace wake.
 * Blue Team arrives at Onyx aboard the captured Covenant destroyer Bloodied Spirit, and links up with Kurt-051, Kelly-087, Dr. Halsey, Chief Mendez, and the SPARTAN-III's. They procede to push foreward into Zone 67.
 * Battlegroup Stalingrad arrives at Onyx to retrieve the survivors, but is unsuccessful due to the Covenant presence. The UNSC battlegroup is destroyed.
 * Kurt-051 and his forces procede to destroy the Sentinel factory in Onyx's polar region and retrieve Team Katana, cryogenically frozen in Slipspace Field Pods.
 * Onyx is found to be an artificial Shield World built by the Forerunners.
 * Fred-104 is promoted to Lieutenant, Junior Grade by Kurt.
 * Kurt-051 dies after detonating 2 FENRIS warheads inside the Onyx Shield World structure.
 * Halsey and the other survivors hold off pursuing Covenant troops long enough to flee to the safety of the Shield World and seal the entrance.
 * Sentinels annihilate the remaining Covenant forces as Onyx's artificial landmass disintegrates.
 * The Battle of Onyx ends.
 * The Arbiter is sent to Delta Halo to retrieve that installation's Index. The Arbiter is successful, but is then betrayed by Tartarus, who casts the Arbiter into the depths of the ringworld. The Arbiter is subsequently captured by Gravemind.
 * Gravemind sends John-117 and the Arbiter to secure the Index and prevent the installation from being activated. SPARTAN-117 is teleported to High Charity while the Arbiter is teleported close to the Control Room. Both are aided by the chaos of the Covenant civil war.
 * SPARTAN-117 is unable to prevent the Index from leaving High Charity with Tartarus. Instead, on the advice of Cortana, the Spartan stows away aboard the Forerunner Dreadnought that is carrying the High Prophet of Truth to Earth. Cortana remains behind to ensure the destruction of Installation 05, should that become necessary.

November 3 through November 7
 * Cortana sends a slipspace message to Earth informing them that SPARTAN-117 is en route.
 * The Arbiter reaches the Control Room but is unable to prevent Tartarus from activating the ring. With the help of humans and the Sangheili, the Arbiter kills Tartarus. This allows Commander Keyes to physically remove the Index from the Core, temporarily interrupting the firing sequence.
 * Due to the interruption, Installation 05 automatically sends a signal to all other Forerunner installations in the galaxy, activating and placing them in standby mode.

November 8
 * The Prophet of Truth arrives in the Sol system aboard the Forerunner Dreadnought, and proceeds on course towards Earth at near-relativistic speeds.

November 8 through November 17
 * The Battle of Mare Erythraeum takes place on Mars, resulting in a victory for the Covenant Loyalists. Following the battle, Colonel James Ackerson, leader of the UNSC forces on Mars, is taken hostage and interrogated by the Jiralhanae Commander Lepidus onboard the Covenant cruiser Triumphant Declaration, who tells them of a Forerunner device linked to the Halo Array known as the Key of Osanalan, and that it can be found in Cleveland, Ohio.
 * Battle of Cleveland: The Covenant Loyalist Army invades Cleveland via the cruiser Harbinger of Piety. The Loyalist forces, under the direction of the Minister of Inquisition, are searching for the whereabouts of the Key of Osanalan (In reality, the Key of Osanalan was made up as a ploy by James Ackerson to prevent Cleveland from being glassed and to save the life of his brother Ruwan.) When Ruwan learns the reason the Covenant are invading, he devises a plan with Sergeant Twyker, involving being injected with organic tracking material. Ruwan confronts Lepidus at Chagrin Falls and tells him that he is the Key of Osanalan. Ruwan is taken onboard the Harbinger of Piety to meet with the Minister of Inquisition, who vows to spare Earth in exchange for Ruwan's knowledge. Ruwan plays along until the Prophet informed him that he knew of the organic tracking material, believing it to be a rescue beacon. In reality, it was a tracking vector. With his last words, he told the Prophet to "kiss [his] ass" right before Nassau Station used its Magnetic Accelerator Cannon to destroy the Harbinger of Piety.
 * Lepidus realizes that the Key of Osanalan does not exist, and returns to the Triumphant Declaration to confront Colonel Ackerson about this deception. Ackerson mocked the Brute Chieftain, saying that his belief in the Key of Osanalan was just one example of how their pompous arrogance would cost them the war. Moments later, Ackerson is beheaded by Lepidus.
 * Sergeant Major Johnson arrives back on Earth and gets clearance from Lord Hood to question Vergil about the artifact the High Prophet of Truth is digging up near Voi.

November 17
 * The Forerunner Dreadnought enters Earth's atmosphere. On-board is Master Chief Petty Officer John-117, who ejects from the ship, using a hatch as a heat shield upon re-entry. Meanwhile, Battle of Sector Six takes place at Pawa, Afghanistan. There, numerous Marines of the 2nd ODST Battalion track SPARTAN-117's descent. SPARTAN-117 eventually lands in the East African jungle near Mount Kilimanjaro, going unconscious for hours.


 * The Prophet of Truth's Dreadnought lands in the middle of the Portal near Voi, Kenya. During the last few weeks, Truth's fleet of twenty-odd battlecruisers and two assault carriers have almost entirely uncovered the Portal and occupied the entire region surrounding it.


 * UNSC forces recover John-117 from a jungle near Mount Kilimanjaro. In the underground facility of Crow's Nest, a plan is formulated to launch an aerial strike on Covenant anti-air defenses in the town of Voi in order to prevent the Prophet of Truth from activating the Forerunner artifact. After repelling a Covenant assault in Crow's Nest and destroying the base in the process, a UNSC strike force led by John-117 retakes the Covenant-held Tsavo Highway.


 * Battle of Voi: John-117 and a Marine strike force enter Voi and gradually push back the city's Covenant occupiers, destroying the Covenant anti-air defenses in the city. An aerial strike force consisting of two frigates and numerous Longsword fighters assaults the Forerunner Dreadnought resting over the Portal artifact, but are unsuccessful in damaging the ship. Truth activates the portal and retreats through it to Installation 00 along with his forces. At the same moment, a Flood-controlled ship slips in, crashing in Voi.




 * UNSC forces make their way toward the crashed ship in order to overload its reactors and contain the Flood outbreak, just as the Sangheili Fleet of Retribution arrives and drops in reinforcements. After recovering a message by Cortana from the Flood ship, John-117 and the remaining human and Sangheili forces retreat from Voi, as the Fleet of Retribution glasses the city and its surroundings in order to contain the Flood.


 * UNSC and Sangheili leaders gather aboard the Sangheili assault carrier Shadow of Intent to hear Cortana's message, which reveals there is a way to stop the Flood on the other side of the Portal. Despite Lord Hood's urging, Commander Keyes, along with the Master Chief and the Sangheili, enter the Portal with the Fleet of Retribution and two UNSC frigates.

December
December 11


 * The Battle of Installation 00: The joint Sangheili-human force arrives at Installation 00 and immediately engages Truth's forces while the deploys ground forces to locate Truth. Despite being outnumbered three to one in space, the separatist fleet makes short work of the Covenant space forces. After locating Truth, the separatist-UNSC alliance launches an assault on the Ark's Citadel where Truth intends to activate the Halo Array. At the same time the former Covenant city ship High Charity arrives from slipspace and crashes on the Ark. Debris spread from the city-ship helps spread a new Flood infestation on the Ark.


 * Truth is killed after John-117 and the Arbiter successfully attack the Citadel. Soon after, it is discovered that the Ark's foundry has created a replacement for the destroyed Installation 04. Realizing that the ring could be used to fire a tactical pulse which would eliminate the Flood infestation, John-117 decides to light it. In order to do so, he enters the ruins of High Charity and recovers Cortana, who still possesses the Activation Index from the original Installation 04. High Charity is destroyed in the process.


 * With the Index secure, John-117, Cortana, the Arbiter, and Sergeant Major Johnson travel to the replacement Installation 04, while the rest of the UNSC and Sangheili forces return to Earth on the Shadow of Intent. In the control room, Johnson is killed as 343 Guilty Spark attempts to prevent him from activating the ring prematurely, as doing so would destroy the ring. John-117 destroys the monitor and begins the firing sequence for the Halo ring. SPARTAN-117 and the Arbiter then escape the control room by taking Johnson's Warthog to the Forward Unto Dawn, which is holding position nearby.


 * Due to the unstable, incomplete nature of the ring as it fires, the slipspace portal collapses as the Dawn enters it, causing it to be sheared in two. Cortana and SPARTAN-117 are in the hangar area at the time of the separation, and are thus left in the aft section of the ship, which falls out of Slipstream space at an unknown location, eventually drifting towards an unidentified planet.

December 23
 * Arbiter Thel 'Vadam returns to Earth using the forward half of the Dawn, crashing into the Indian Ocean.

December 31
 * Codename: SURGEON filed a report to Codename: USUAL SUSPECTS entitled "Historical/Psychological Analysis of Cole, Preston J." The report was filed from in synchronous orbit on the far side of Luna.

Battles
Human-Covenant War
 * Battle of Sigma Octanus IV
 * Battle of Tribute
 * Battle of Verge
 * Battle of Line Installation 1-4
 * Fall of Reach
 * Battle of Viery
 * Operation: UPPER CUT
 * Raid of New Alexandria
 * Battle of Aszod
 * Battle of Installation 04
 * Raid on the Truth and Reconciliation
 * Battle of the Silent Cartographer
 * Massacre at Eridanus Secundus
 * Operation: FIRST STRIKE
 * Battle of Earth
 * Battle of Ross Island
 * Battle of Mombasa
 * Battle of Havana
 * Battle of Cleveland
 * Battle of Sector Six
 * Battle of Voi
 * Battle of the Gas Mine
 * Battle of Installation 05
 * Battle of Onyx
 * Battle of Mare Erythraeum
 * Battle of Installation 00

The Great Schism
 * First Battle of High Charity

Quarantine of the Flood
 * Battle of Installation 05
 * Battle of the Quarantine Zone
 * Second Battle of High Charity

Human

 * General Kits
 * Vice Admiral Danforth Whitcomb
 * Vice Admiral Roland Freemont
 * Vice Admiral Hieronymus Michael Stanforth
 * Admiral Carl "Buster" Patterson
 * Colonel James Ackerson
 * Rear Admiral Ned Rich (According to the ONI Memorial.)
 * Colonel Herzog
 * Colonel Felicia Sanderson
 * Colonel Teller
 * Unnamed UNSC Colonel
 * Unnamed Bumblebee Pilot
 * Unnamed Female Corporal
 * Captain Jacob Keyes
 * Captain Aaron G. Gibson (According to the ONI Memorial.)
 * Captain Greene
 * Captain Moreland
 * Dr. Endesha
 * Lieutenant Commander Kurt Ambrose
 * Lieutenant Commander Miranda Keyes
 * Lieutenant Commander Gail Purdy
 * Major Antonio Silva
 * Commander Jerome G. Ortega (According to the ONI Memorial.)
 * Lieutenant Dominique
 * Lieutenant Frye
 * Lieutenant Hall
 * Lieutenant Rick Hale
 * Lieutenant Elias Haverson
 * Lieutenant Aki Hikowa
 * Lieutenant Peterson
 * Lieutenant, Junior Grade David Brightling
 * Lieutenant, Junior Grade Bill Streeter
 * First Lieutenant Buckman
 * First Lieutenant Jake Chapman
 * First Lieutenant Melissa McKay
 * Second Lieutenant Dalu
 * Second Lieutenant McCasky
 * Second Lieutenant Oros
 * Ensign Ellen Dowski
 * Ensign William Lovell
 * Flight Officer Captain Carol Rawley
 * Warrant Officer Shiela Polaski
 * Chief Petty Officer Thom Shephard
 * Chief Petty Officer McRobb
 * Petty Officer First Class Mary Murphy
 * Petty Officer Third Class Samuel N. Marcus
 * Petty Officer Third Class Pauley
 * Sergeant Major Avery J. Johnson
 * First Sergeant Tink Carter
 * Master Sergeant Lister
 * Gunnery Sergeant Waller
 * Staff Sergeant Marvin Mobuto
 * Sergeant Thomas Chang
 * Sergeant Zhao Heng Lopez
 * Sergeant Corly
 * Sergeant Parker
 * Corporal Jason Morelli
 * Corporal Errera
 * Corporal Locklear
 * Corporal Lovik
 * Corporal Mitchell
 * Corporal Perez
 * Corporal Yutrzenika
 * Lance Corporal "Snaky" Jones
 * Lance Corporal Eugene Yate
 * Private First Class Hosky
 * Private First Class M. Fitzgerald
 * Private First Class Wallace A. Jenkins
 * Private Bisenti
 * Private Kappus
 * Private Manuel Mendoza
 * Private Marie Postly
 * Private McKenzie
 * Private O'Brien
 * Private Riley
 * Private Satha
 * Private Marie Postly
 * Corpsman "Doc" Valdez
 * Crew Chief Cullen
 * Flight Officer Mitchell
 * Crewman Singh
 * Hospital Corpsman Ngoc Benti
 * Governor Jacob Jiles
 * War Photographer Jake Courage
 * Ruwan Ackerson
 * Laszlo Sorvad
 * Patrick Rimmer
 * Clarence
 * Devesh Bhasin
 * Gage Yevgenny
 * Eric Santiago
 * Sita
 * Orrin
 * Dale
 * Amey
 * Charleston
 * Connor Brien
 * Amey
 * Kowalski
 * Hague
 * Burgundy
 * Dawkins
 * Suzuki
 * Al-Thani
 * Nixaliz
 * Vern
 * William-043
 * Jorge-052
 * Malcolm-059
 * Isaac-039
 * Vinh-030
 * Grace-093
 * Li-008
 * Joshua-029
 * Anton-044
 * Catherine-B320
 * Carter-A259
 * Emile-A239
 * SPARTAN-B312
 * Holly-G003
 * Dante-G188
 * Thom-293

Covenant
Sangheili
 * Imperial Admiral Xytan 'Jar Wattinree (Presumed dead by the NOVA activation near Joyous Exultation)
 * Fleetmaster Voro Nar 'Mantakree
 * Fieldmaster Noga 'Putumee
 * Heretic Commander Sesa 'Refumee
 * Shipmaster Lat 'Ravamee
 * Shipmaster Tano 'Inanraree
 * Special Operations Officer Zuka 'Zamamee
 * Ado 'Mortumee
 * Isna 'Nosolee
 * Soha 'Rolamee

San 'Shyuum
 * High Prophet of Regret
 * High Prophet of Mercy
 * High Prophet of Truth
 * Truth and Reconciliation's Prophet
 * Minister of Etiology
 * Minister of Inquisition

Jiralhanae
 * Chieftain of the Jiralhanae Tartarus
 * Ceretus
 * Jiralhanae Chieftain Parabum
 * Maladus
 * Facius
 * Hammadus
 * Jupentus
 * Brunus
 * Golubus

Unggoy
 * Gagaw
 * Linglin
 * Yayap
 * Zawaz
 * Kwassass
 * Flipyap
 * Mehmep

Yanme'e
 * Hopalong

Forerunner

 * 343 Guilty Spark
 * 032 Mendicant Bias (Presumed destroyed with the Ark)

Flood
 * Gravemind

Trivia
The first and second parts of 2552 equal 2+5=7 and 5+2=7, another one of Bungie's 7 references.