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The Halo Story

Halo Story Timeline (so far...)

Halo: The Fall Of Reach
Halo: The Flood
Halo: First Strike
Official Backstory (
Halo 2
Halo: Ghosts Of Onyx
Contact Harvest
Halo Wars
Halo: Uprising (Marvel)
Halo Graphic Novel
Halo 3

2160-2200 This period in human history was marked by a series of brutal conflicts between various governments and factions in our Solar System. Conflicts of particular historical importance included the Jovian Moons Campaign, The Rain Forest Wars, and a series of clashes on Mars.

As overpopulation and political unrest on Earth increased, a number of new political movements formed. The most noteworthy dissident movements of the period were the "Koslovics" and the "Frieden" movement. The Koslovics—supporters of neo-Communist hardliner Vladimir Koslov—sought a return to the glory days of Communism and the elimination of corporate and capitalist influence, particularly in orbital facilities and offworld colonies.

The Frieden movement was a resurgence of fascism, springing from anti-Koslovic sentiment that had taken root in the Jovian colonies (largely backed by Unified German Republic corporations, frequent targets of Koslovic "workers' crusades"). "Frieden" literally means "peace." In this case, they believed that peace could be achieved only once the "oppressors on Terra Firma" were eliminated.
2160 March-June: The Jovian Moons Campaign began. Jovian secessionist attacks on United Nations Colonial Advisors on the moon Io led to three months of fighting between the Earth military and Jovian "Frieden" forces. Though this was not the first armed conflict in our Solar System, it was easily one of the bloodiest, and is generally considered to be the spark of increased friction and militarization that followed.

The Jovian Moons Campaign escalated tensions, as Earth's national governments-many of which sponsored colonies within the system-began fighting proxy wars off-planet. As these proxy wars continued, tensions on Earth mounted, leading to a number of armed conflicts on Earth itself.
2162 The Rain Forest Wars: Armed conflict ripped through South America, as Koslovic, Frieden, and UN forces all clashed over ideological differences, sparking additional conflicts off-planet.
2163 December: In a conflict that stemmed from the Rain Forest Wars, the three primary Earth factions clashed again, this time on Mars. A series of lightning strikes against Koslovic forces near the Argyre Planitia marked the first extra-terrestrial deployment of Marines. The campaign was an unqualified success. As a result, future military doctrine favored large contingents of Marines for ground assaults and ship-boarding actions.
2164 UN-sponsored military forces begin a pattern of massive buildups, culminating in the first real interplanetary war. After the successful Marine deployment on Mars, recruitment drives and propaganda tactics strongly bolster UNSC (UN Space Command) forces. UN forces defeat Koslovic (supporters of rabid Communist hard-liner Vladimir Koslov) and Frieden (a resurgence of fascism) forces on Earth, then begin a systematic and dedicated drive to crush their remnants on the various planets they hold throughout the system. At the conclusion, Frieden and Koslovic forces are defeated, in the face of a massive, unified and very powerful UN military.

The novel A Soldier's Tale: Rainforest Wars is first published, considered a classic military novel depicting the historical events that occurred during the Rain Forest Wars.
2170 A unified Earth government was formed in the wake of the conflicts of 216. Now, the victors were forced to deal with a less obvious but equally serious threat: overpopulation and a massive military that had no enemy to fight.

In the postwar period there were massive population surges and the overpopulation, coupled with the destruction and famine bred by the Rain Forest Wars, threatened to destabilize the economy.
2291 A team of researchers, physicists, and mathematicians working in secret developed the Shaw-Fujikawa Translight Engine, a practical means of propelling spacecraft across vast interstellar distances. This new engine allowed ships to tunnel into "the Slipstream" (also called "Slipspace"). Slipspace is a domain with alternate physical laws, allowing faster-than-light travel without relativistic side-effects. Faster-than-light travel is not instantaneous; "short" jumps routinely take up to two months, and "long" jumps can last six months or more.

The SFTE generated a resonance field, which when coupled with the unusual physics of the Slipstream, allowed for dramatically shorter transit times between stars; however, scientists noted an odd "flexibility" to temporal flow while inside the Slipstream. Though no human scientist is sure why travel time between stars is not constant, many theorize that there are "eddies" or "currents" within the Slipstream-there is generally a five to ten percent variance in travel times between stars. This temporal inconsistency has given military tacticians and strategists fits-hampering many coordinated attacks.
2310 The Earth government unveils the first in a line of colony ships; given conditions on Earth are deteriorating in the face of overpopulation, hitching a ride out to a colony becomes a highly attractive option. Additionally, the Earth government plans to attach military personnel to each colony, to help better utilize the massive (and expensive) standing fleets. Because FTL travel is still fairly new and expensive, colonists and military personnel face a stringent regimen of physical and mental testing. In theory, only the best-qualified citizens and soldiers are allowed to colonize "nearby" worlds. This is the birth of the Inner Colonies; typically Inner Colonials are—later in the timeline—considered the elite, the best and brightest.
Jan 1
The Odyssey is launched. The lead ship in the colony vessels, the Odyssey—laden with troops and terra forming gear—spearheads the colonization of a new world. This sparked the first wave of human expansion beyond the confines of the Solar System.
2390 The colonization of the Inner Colonies was fully underway. There were 210 human-occupied worlds in various stages of terraforming, and the population burden across human-controlled space was largely stabilized.
2468 The outer colony of Harvest is founded, and the Tiara space station is constructed.
2473 The Phoenix-class colony ship UNSC Spirit of Fire is constructed.
2490 Expansion continued at a rapid pace, and by 2490 human space encompassed more than 800 worlds throughout the Orion Arm of the Milky Way (ranging from fairly well-tamed planetary strongholds to tiny hinterland settlements). Outward expansion continued, and the Inner Colonies become a political and economic stronghold, though they relied heavily on raw materials supplied by the Outer Colonies.

During this period, the planet Reach (orbiting Epsilon Eridani, right on Earth's metaphorical doorstep) became the UNSC's primary Naval yard and training academy. Reach was a major producer of warships and colony vessels, as well as a training ground for covert operatives and Special Forces.
2491 The ORION Project, the predecessor of the SPARTAN-II Program is initiated by the Office of Naval Intelligence.
2492 The UNSC issues a Code: BANDERSNATCH, permitting the usage of nuclear weapons to destroy a massive rebellion that could not be held under control on the colony of Far Isle.
2494 First rebel insurrection in Eridanus system.
2495 The UNSC Hopeful becomes the largest mobile military hospital in history, complete with fusion reactors and a Shaw-Fujikawa Slipspace Drive. Battered in several engagements from rebel skirmishes to Covenant assaults, the UNSC Hopeful remains under the command of Admiral Ysionris Jeromi.
2496 The Eridanus insurrection is defeated by UNSC forces.
Mar 13
Operation: KALEIDOSCOPE, a plan conceived by ORION Project officials commences. Jerald Mulkey Ander, one of the leaders believed to be in charge of the Secessionist Union (People's Occupation Government) is assassinated on Harvest by Avery J. Johnson, a young Corporal in the UNSC Marine Corps.
2510 The structural system for the Pillar of Autumn is designed by Dr. Robert McLees at the Reyes-McLees Shipyards over Mars.
2512 A geological survey team on Sigma Octanus IV finds rocks with odd compositions. These were introduced from meteor impacts roughly 60,000 years ago.
2513 Second rebel insurrection in Eridanus system, led by Colonel Robert Watts, is suppressed by the UNSC in operation TREBUCHET. Watts is driven into the local asteroid belt.

Brain mutations are outlawed by UNSC MED CORPS.

The 1st Battalion of the 21st Marine Division - an element of the UNSC's 9th Marine Expeditionary Force - led by Colonel Ponder was sent on Eridanus II in an attempt to capture Insurrectionist leaders and put down the Eridanus Rebellion as part of Operation: TREBUCHET. The mission, however, ended in one of the insurrectionist leaders' family getting killed in Elysium City, and Colonel Ponder being injured in action and demoted to Captain.
Aug 17
Dr. Halsey and Lieutenant Keyes meet 6-year-old John on a playground in Elysium City, Eridanus-2.
Sep 23
Project SPARTAN II begins on Reach with 75 conscripts. Project SPARTAN is an attempt to develop an effective, surgical military team to relieve political tensions and circumvent civil war.
Jul 12
John makes squad leader.
2520 The Phoenix-class colony ship UNSC Spirit of Fire is refit as a military warship.
Jul 14
SPARTAN Training exercise: Capture the Flag against Tango Company.
Jun 16
As part of Operation: TREBUCHET, two four-man teams led by Staff Sergeants Nolan Byrne, and Avery J. Johnson (backed by the UNSC corvette Bum Rush hovering in high-orbit, and transported via two AV-14 Hornet fast attack aircrafts) infiltrate the city of Casbah on the outer colony of Tribute as ordered by Colonel Aboim. Their objective is to eliminate Insurrectionist bomb engineers. Although the UNSC Marine squads succeed in neutralizing an explosives-manufacturing facility, some of the Insurrectionists - armed mainly with handguns - smuggle the bombs into Casbah, the main population center of Tribute. The situation worsens, leading to a hostage crisis at one of the Jim Dandy restaurants where 38 civilians, 2 rebels and 3 of Sergeant Byrne's marines are killed, Byrne and Johnson themselves being wounded.
Minor Transgression, a Jackal-operated ship arrives in the Epsilon Indi System and discovers the human colony world of Harvest. The Luminary (a Covenant device designed to detect Forerunner artifacts) onboard the vessel pinpoints several thousands of Forerunner relics, including an Oracle, all registered on the surface of Harvest. The Jackals seize the opportunity to claim some of the relics for themselves before informing the Covenant High Council, and begin assaulting UNSC freighters (including the UNSC Horn of Plenty). The Office of Naval Intelligence responds to the mysterious attacks, misinterpreting them for Insurrectionist raids. Setting up a well-organized task force, Sergeants Avery Johnson and Nolan Byrne ambush the Jackals onboard one of the UNSC's freighters, foiling the aliens' plans to land on Harvest, and delaying a potential invasion. Two survivors - the Grunt Deacon Dadab and the Engineer "Lighter Than Some" - flee the skirmish in an escape vessel. Following the engagement, the UNSC mobilizes the Colonial Militia (a reserve branch of the UNSC Army intended to defend a colony and protect its citizens in case of an enemy invasion) to confront a possible assault from this "new enemy".
Feb 3
Contact with Harvest, an outer colony, is lost shortly after the colony itself had made contact with an unknown object. The Colonial Military Administration sends the scout ship Argo to investigate.
Feb 11
Two members of the Covenant High Council - the Minister of Fortitude and the Vice Minister of Tranquility - conceive a plan to overthrow the Covenant Hierarchs in order to lay hold of the enormous amount of Forerunner relics. Political discords within the Covenant hierarchy determine the Ministers to utilize the Rapid Conversion - a Brute-controlled vessel guided by Chieftain Maccabeus and his crew - to lay siege on Harvest and gain control of the relics, without giving the Elites a chance to tip the power balance. Upon the ship's arrival in the Epsilon Indi System, the Brutes spot Deacon Dadab and Lighter Than Some's emergency escape vessel. Chieftain Maccabeus uses his finding as a profitable way to boost his Grunts' morale, and repair the ship's damaged sections - which he intentionally wrecked - with help from Lighter Than Some.

The two AI's controlling the planet Harvest (Sif and Mack) design a peace message in the form of an image in an attempt to establish peaceful relations with the aliens. The peace offering fails after a disoriented Grunt fires on a colonial militiaman, leading to the Brutes' onslaught upon the human colony.
February - October
After putting their coup to work, the Minister of Fortitude and the Vice Minister of Tranquility request the advice of an Oracle onboard the Forerunner Dreadnought. The Oracle reveals that Harvest does not hold Forerunner artifacts, but human settlements which the Covenant had mistakenly considered as being of Forerunner origin, claiming that the humans are actually "Reclaimers" or "living Forerunners". Having learned this, the two Ministers take their plan one step further, and uphold secrecy regarding the presence of living Forerunners on Harvest, as to avoid a major crisis which could ultimately lead to the downfall of the Covenant.
Feb 23
As the Brutes begin to devastate Harvest, Colonial Militia forces evacuate civilians out of the major cities and ferry them to the capital city of Utgard. In an effort to save as many Harvesters as possible, the Colonial Militia transports the civilians to the orbital space station Tiara, which supports the seven space elevators of Harvest, and aboard the UNSC freighters. After several attempts to defeat Sergeant Avery Johnson's task force on the Tiara, the ten-Brute team led by Tartarus (a young Brute pack leader) is betrayed by Dadab and Lighter Than Some, hindering his chance to stop the Harvesters onboard the freighters to flee to safety.

Harvest is glassed, and the remaining survivors onboard the freighters are transported away from the devastation. Following the coup, the Minister of Fortitude and the Vice Minister of Tranquility become the High Prophets of Truth and Regret. Using the Luminary's guidance to discover human colonies, the Covenant declares war on humans in order to safeguard its place in the Forerunners' history.
Apr 20
The Argo arrives in-system and makes one confirmation transmission. No further reports are received.
Mar 9
The SPARTANs undergo a radical series of biological, neurological, and physiological alterations. 30 die, 12 are permanently disabled, and 33 successfully adapt.
Sep 12
The SPARTANs first "official" mission, to infiltrate the rebel base on Eridanus to capture the rebel leader, Colonel Robert Watts, is successful.
Oct 7
A UNSC battle group, consisting of the destroyer Heracles, under Captain Veredi, and the two frigates Arabia and Vostok, enters the Harvest system and discovers that everything on the planet has been completely incinerated and the surface melted down to glass. In orbit around the remains of the colony world is a single alien ship, which proceeded to attack the battle group, destroying both Arabia and Vostok and badly damaging the Heracles. Intercepted communications identify the enemy as The Covenant. The message "Your destruction is the will of the Gods... and we are their instrument" is broadcast in UNSC language.
Nov 1
Vice Admiral Preston Cole mobilizes the largest fleet in human history to retake Harvest.
Nov 2
The SPARTANs learn of the attack of the Covenant at Harvest and Project MJOLNIR commences. CPO Mendez leaves to train next group of SPARTANs.
Nov 27
Project MJOLNIR, a comprehensive package of scientifically enhanced armor, custom-tailored to the biologically augmented SPARTANs, is introduced to John and his squad at the UNSC Damascus Materials Testing Facility, on the planet Chi Ceti-4. The SPARTANs (now decked out in Mjolnir armor) destroy a Covenant ship by carrying a nuke onboard, inside the energy shield.
2530 The outer colony of Eridanus II is destroyed by the Covenant.
2531 Cole's war fleet engages the alien warship responsible for the decimation of the colony, scoring a victory (though the battle cost Cole two-thirds of his battle group). Only a last minute tactical inspiration turned the tide of battle.

After returning to Earth, Cole—promoted to Admiral—learns that a number of outlying colonies have been destroyed, leaving behind no survivors. Cole begins to move his fleet around, trying to intercept the invaders. Ground and ship-to-ship battles begin in earnest, raging throughout the Outer Colonies. During one ground engagement, Human forces capture one of the aliens. Before succumbing to his wounds, interrogators learn that the aliens refer to themselves as "the Covenant" (roughly translated).
May 1
Spartan-II Blue Team is deployed on planet Victoria, located in the 111 Tauri System. Their mission is to infiltrate a United Rebel Front outpost and retrieve several stolen UNSC nuclear warheads. The operation is a success, leading to the death of General Howard Graves - one of the people speculated to be in charge of the United Rebel Front.
Nov 7
SPARTAN-051, Kurt, is covertly reassigned to ONI Section Three and tasked with secretly training a new generation of soldiers, the SPARTAN IIIs, assisted by CPO Mendez and under the authority of Colonel Ackerson. He is promoted to Lieutenant and is given the last name Ambrose.
2535 In the course of four short years, Cole's forces are hammered, despite his excellent leadership and tactical brilliance. It is simply a matter of being outgunned; Covenant kill ratios tend to top four to one in ship-to-ship combat. By 2535, virtually all of the Outer Colony worlds have been destroyed by the Covenant. The "Cole Protocol" is established by military order: all human vessels must ensure that Covenant forces do not find Earth. Human ships must-when forced to withdraw-not move on to an Earth bound vector, even if that means jumping without proper navigational calculations. If blind jumps are not possible, the ship's captain must order self-destruction if capture is imminent. In addition, it is also imperative that the powerful ship A.I. data cores not fall into Covenant hands, so part of this protocol involves either the removal or destruction of the ship's A.I. in extreme situations.
Feb 12
Jericho VII in the Lambda Serpentis system falls. Master Chief, on board the UNSC Destroyer Resolute under Captain de Blanc, is allowed to view as the Covenant fleet glasses the planet.
2536 Covenant forces begin to swarm into the Inner Colonies. For several years the war falls into a pattern: humans win isolated battles, typically during ground operations, but at a horrible cost. In space combat, the humans are losing at a precipitous rate, and one by one, the colonies fall.
July 27
SPARTAN III Alpha Company begins Operation PROMETHEUS, to disable as much of the Covenant orbital shipyard K7-49 as possible. In a little over a week, the shipyard is completely shut down, at the loss of the entire company of SPARTANs.
2537 An armed insurrection takes place on the colony world of Mamore.
2539 SPARTAN III Beta Company Team X-ray vanishes while on a routine exercise north of Camp Currahee on the planet Onyx in the Zeta Doradus system. ONI fences off the area, designates it "Zone 67," and declares it absolutely off-limits.
July 3
SPARTAN III Beta Company is delivered to Pegasi Delta onboard the All Under Heaven, beginning Operation TORPEDO, the destruction of a Covenant refinery. The operation is a success, although all but two of Beta Company, Tom (B292) and Lucy (B091), are lost.
2547 Section Two of the Office of Naval Intelligence publicly announces the existence of the SPARTAN-II Program in an effort to boost morale throughout the UNSC.
2549 Sergeant Avery Johnson encounters the Boren's Syndrome due to intense exposure to radiation.
2550 The Pillar of Autumn is refit to serve near Zeta Doradus.
Feb 19
Biological augmentation of SPARTAN III Gamma Company, including significant brain chemistry modifications designed to enhance primitive survival responses in times of extreme stress, authorized by Lieutenant Ambrose.
Jul 17
A Covenant fleet is discovered by Ensign William Lovell on UNSC Remote Scanning Outpost Archimedes, entering the Sigma Octanus system. Commander Keyes, on board the UNSC Destroyer Iroquois, takes on 4 medium-tonnage Covenant craft (two frigates, one destroyer, one carrier), and destroys 3 of them in what becomes known as the 'Keyes Loop'. The Carrier heads to Sigma Octanus IV and drops Covenant troops, invading the city of Cote D'Azur. Keyes is promoted to Captain by Admiral Stanforth.
Jul 18
The SPARTANs and the Marines engage Covenant forces on the ground, eventually nuking Cote D'Azur and most of the Covenant invasion force (but very few humans), while 4 dozen UNSC ships engage 20 Covenant craft. Seven human craft survive. The Iroquois destroys a stealth ship receiving an encrypted transmission from the surface. Once this ship is destroyed, the 7 surviving Covenant ships break off and flee. The Iroquois heads back to Reach for debriefing. A Covenant tracker attaches itself, unseen, to the Iroquois' hull.
Aug 12
The Master Chief is debriefed by ONI at Camp Hathcock, Reach, on the events of Cote D'Azur.
Aug 25
The Pillar of Autumn is chosen by Dr. Halsey and Cortana (with Keyes as Captain) to handle a secret mission that Dr. Halsey is planning.
Aug 27
John rejoins the remaining SPARTANS (except for three that are otherwise engaged - Gray team) in 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.
Aug 29
The Master Chief gets a neural interface upgrade and new armor with built-in Covenant shield technology. He is also introduced to Cortana, an A.I. created from Dr. Halsey's own neural patterns.
Aug 30
Cortana gets revenge on Colonel Ackerson, part of ONI's Special Warfare branch, for attempting to eliminate Cortana and Master Chief - she gets him transferred to the front. Bypassing several other colonies, the Covenant arrive at Reach and begin what has become all too familiar to the embattled Human forces: the destruction of the planet.
Aug 30
The remaining SPARTANS are divided into two teams: Red and Blue. John and the rest of Blue team (Linda and James), while on an orbital mission to ensure that a NAV database stays out of Covenant hands, end up onboard the Pillar of Autumn when she jumps away from the Reach system to evade Covenant forces. James is lost and Linda is mortally wounded, and the subsequent mission on Halo is left to the Master Chief to complete.

The Covenant take the surface of Reach, and Red team splits, one group to retrieve Admiral Whitcomb, while the rest hole up in ONI's Castle Base underground facility with Dr. Halsey. The Spartans receive parts of a MJOLNIR Mark V upgrade and new weapons, while Dr. Halsey learns of Colonel Ackerson's mysterious plans, plans that seem to involve "her" Spartans.
Sep 4
Lieutenant Wagner returns to Earth and reports on the evident destruction of Reach to Colonel Ackerson, Admiral Hood, and General Strauss at an ONI facility in Sydney, Australia.
Sep 7
The Time/Date Record Anomaly of Sep 23, 2552 most likely rejoins the timeline here. Dr. Halsey and members of Red team discover an enigmatic shard in an ancient installation below the ONI facility. Blue team joins with team Gamma to retrieve Admiral Whitcomb, and rejoin the rest of Red team who have been besieged by the Covenant, who apparently revere the artifact that the humans have found. Dr. Halsey destroys ONI's underground facility CASTLE BASE on Reach, preventing the Covenant from gaining control of its secrets.
Unknown 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 Gettysburg/Ascendant Justice, and discover that the shard seems to have the ability to bend both space and time.
Sep 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 ship (the Beatrice), a Chiroptera-class vessel, the smallest UNSC classification that contains an SFTE. Before she goes, she gives the alien artifact to Corporal Locklear, with implicit instructions to destroy it.
Sep 13
Admiral Whitcomb and Lieutenant Haverson destroy the majority of the surrounding Covenant fleet by detonating the Unyielding Hierophant. John, Linda, Will, and Fred, the last known remaining Spartans, along with Sgt. Johnson, and, of course, Cortana, depart for Earth to warn of the impending Covenant invasion.
Sep 19
The Pillar Of Autumn arrives at Halo. A company of Orbital Drop Shock Troopers (UNSC Naval Special Forces) led by Major Antonio Silva and his second in command, Lieutenant Mellisa McKay land on Halo via 'Human Entry Vehicles' and establish an operational firebase situated near a mesa a few kilometers away from the Pillar of Autmun's crash site. Alpha Base, as it was designated, had been supplied and heavily fortified with what remained of the Pillar of Autmun's arsenal.

Believing that the Master Chief was hiding out at Alpha Base, Covenant ground and aerial forces commanded by Zuka 'Zamamee and Noga 'Putumee attack the base in an effort to capture the Chief. The attack fails and the base is held by Major Silva.
Sep 22
The Master Chief and Cortana, onboard a Longsword in the debris field of the destroyed Halo, find one remaining Pelican containing Sgt. Johnson, Lieutenant Haverson, Warrant Officer Polaski, Corporal Locklear, and a set of cryotubes containing Spartan 058, Linda.

Planning to fly the Truth and Reconciliation to Earth, Major Silva and the ODSTs abandon Alpha Base. The captured Covenant ship, however, had been sabotaged by Lieutenant McKay, leading to Major Silva's, the ODSTs and her death.
Sep 23
The Master Chief, Cortana, Linda, Polaski, Sgt. Johnson, Haverson, and Locklear depart for Reach via Slipspace aboard the Covenant Flagship Ascendant Justice, captured near the Halo debris field. A Time/Date Record Anomaly continues from this point in the narrative, resolved above on Sep 7, 2552.
SPARTAN-062 (Maria) tests the Mjolnir MARK VI armor system against a platoon of ODSTs, guided by naval officers at the Songnam Special Warfare Center in Korea. The armor is approved and sent to the Cairo Orbital Defense Platform.

Blue Team responds to Covenant incursions and expeditions on Mount Erebus in the Antarctic and the Yucatan Peninsula. Covenant forces in the Antarctic are eliminated by a HAVOK tactical nuclear missile. These number of Covenant expeditions consisted in geological examinations and excavations of Earth's soil and seabeds.
Oct 20
The Master Chief and Captain Keyes (post-humously) are decorated for their actions on Reach and Halo 04.

Concurrently, the Elite Commander of the Covenant fleet "Particular Justice" is punished for Heresy before being transformed into the Arbiter.

The Prophet of Regret and his relatively minor fleet arrive at Earth presumably looking for Forerunner installations, unaware of its status as the Human homeworld. After a brief conflict and some exploration in Africa, Regret retreats to Delta Halo 05 followed by Miranda and the In Amber Clad.

Four other UNSC vessels, the corvette Coral Sea, the two frigates Redoubtable and Paris, and the prowler Dusk are both close enough to the Slipspace rift and have charged Slipspace capacitors, and attempt to follow the In Amber Clad into the eleven nondimensions of Slipspace.

New Mombasa is destroyed in the Slipspace wake of Regret's ship.
Oct 31
While engaged in a drill near Camp Currahee on the planet Onyx, members of SPARTAN III Gamma Company observe apparently newly-activated Sentinels operating within Zone 67.
UNSC ground forces (possibly UNSC Army) led by Colonel James Ackerson are pinned down against the Covenant Loyalist Army in the Mare Erythraeum basin on Mars. The battle results in a UNSC defeat, and Colonel Ackerson is captured and interrogated by the Brute Commander Lepidus onboard the Covenant cruiser Triumphant Declaration. While being tortured, Ackerson reveals that a certain "Key of Osanalan" located in the city of Cleveland, United Republic of North America on Earth, is required to properly fire the Halo arrays. This later sparks the Covenant Loyalist assault on Cleveland, where combined forces of UNSC Marines and ODSTs attempt to resist the onslaught.
Nov 3
Dr. Halsey and Kelly arrive in the Zeta Doradus system, and are immediately attacked by Sentinels as they approach Onyx. They crash-land the Beatrice, and join forces with Kurt, Mendez, and the Team Saber squad of SPARTAN IIIs. Dr. Halsey coerces the Onyx AI, Endless Summer, to assist them by sending a message through Slipspace warning FLEETCOM about the events currently unfolding at Onyx. As the Slipspace COM probe is launched, the AI detects another message being transmitted from within the Slipspace matrix. It is Cortana, warning FLEETCOM that the Flood, with the help of a previously unknown coordinating intelligence, was attempting to escape Delta Halo.

Blue Team, consisting of Fred, Will, and Linda, is ordered to Onyx to aid Dr. Halsey and the others. They hijack the Covenant cruiser Bloodied Spirit and transition to Slipspace for the journey, only to have the ship automatically drop back into normal space to answer a different distress call. This is from the Covenant ship Incorruptible, commanded by the Elite Voro 'Mantakree, which is being attacked by a Brute-commanded pair of frigates, the Twilight Compunction and the Revenant. The SPARTANS manage to re-enter Slipspace and continue on to Onyx, but not before the Covenant discover who they are and where they are headed.

Dr. Halsey discovers that Onyx is what the Forerunner referred to as a "Shield World", and contains a stable Slipspace rift deep within the planet's structure. As the Covenant close in on the humans within Onyx, Dr. Halsey persuades them all to enter the rift, to escape whatever galactic destruction the Forerunner intended with the Halos that she is convinced is inevitable. Dr. Halsey, Mendez, SPARTAN III Gamma Company Teams Saber and Katana, Tom, Lucy, Fred, Linda, and Kelly all pass through the rift as it closes, as Kurt detonates two warheads within the ammassed Covenant forces. The detonation obliterates much of the planet's organic material, revealing an underlying structure composed entirely of trillions of Sentinels, all focused on protecting the rift.
Nov - Dec
Armament of UNSC Navy and Marine units takes place on Mars, one of the remaining colonies still controlled by the Earth government.
Dec 9
Covenant Loyalists and a combined force of UNSC Special Forces and Marines clash in eastern Afghanistan on Earth. Although suffering heavy casualties, the 2nd Battalion of Orbital Drop Shock Troopers is able to locate the Master Chief's position as he enters the atmosphere.
2552 - 2553
Nov - Mar
After crashing in East Africa, the Master Chief is recovered by a squad of UNSC Marines led by Sergeant Avery Johnson and the Arbiter. The group splits, and attempts to reach the extraction zone. Johnson and his men manage to board a Pelican, but find themselves captured by Brutes shortly afterwards. The Master Chief and the Arbiter find Johnson and his men and rescue them.

The Master Chief, Johnson, and the Arbiter arrive at a five hundred year-old underground UNSC military base near the town of Voi named the "Crow's Nest". Commander Miranda Keyes and Lord Hood plan an attack on the High Prophet of Truth in order to avoid the activation of the Portal, but are interrupted by a detachment of Covenant Loyalists which take over the base.

As Lord Hood orders his remaining ships to attack Truth's fleet, a slipspace entrance is created by the Portal. A Flood-infested vessel carrying a construct identified as Cortana crashes near Voi, and the city is quickly overwhelmed by the parasite. This is in fact a part of Cortana, containing a recorded message.

The construct is retrieved from the ship, and repaired by 343 Guilty Spark. Onboard the Sangheili vessel Shadow of Intent - commanded by Rtas 'Vadumee - the recorded message held within the construct informs Lord Hood and the Master Chief that the Portal holds the secret to the defeat of the Flood.

Passing through the slipspace Portal, Commander Keyes and her fleet arrive at the Ark. After a brief engagement between the UNSC fleet and the Covenant Loyalist fleet, the Master Chief and the Arbiter learn that the Ark is situated beyond the galactic rim, thus safe from the Halos range of fire. Apart from its advantageous location to escape the Flood, it also serves as a construction facility to built replacement Halos in case one is severely damaged or destroyed.

Making her way into the Control Room of the Ark where Johnson is held captive, Commander Keyes is killed by the Prophet of Truth. He uses Johnson to activate the seven Halo rings.

Joining forces with the Flood, the Master Chief and the Arbiter eliminate Truth's defenses, Truth himself being killed. An unexpected turn of events follows, and Gravemind betrays the Master Chief and the Arbiter as Johnson flees onboard a Pelican.

Cortana conceives a plan to destroy the Flood without affecting the Milky Way. Safely distanced from the galaxy, the replacement Installation 04 can eliminate the Flood for good once fired. The Master Chief infiltrates the Flood-infested High Charity, retrieves Cortana and uses the Index from the former Installation 04 to fire the Halo and destroy the Flood and its leader. While attempting to activate the replacement Installation 04, Johnson is killed by 343 Guilty Spark, claiming that a "premature firing" will destroy both the Installation and the Ark.

Guilty Spark is destroyed by the Master Chief, who then activates the Halo and heads towards the UNSC Forward Unto Dawn. The Arbiter and the Master Chief make it onboard the ship, however, the slipspace Portal is deactivated as the Halo stirs. Half of the Frigate containing the Arbiter passes through the Portal, and the other half containing the Master Chief and Cortana stays behind.
Mar 3
The Human-Covenant War ends. A memorial dedicated to the victims of the war is built in Kenya on Earth.

For lack of time, and a better way of displaying the information, the events of Halo 2 can be viewed chronologically here (or here, if summaries are more to your liking).