Post-Covenant War conflicts

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"Humanity stands as the greatest threat in the galaxy. Refusing to eradicate them is a fool's gambit. We squander eons in the darkness, while they seize our triumphs for their own. The Mantle of Responsibility, for all things, belongs to Forerunners alone! Think of my acts as you will. But do not doubt the reality: the Reclamation... has already begun. And we are hopeless to stop it."

— The Ur-Didact in a speech defending his actions to a group of other Forerunners

Following the end of the Human-Covenant War in 2553, the Unified Earth Government and its United Nations Space Command became involved in a number of new conflicts arising from the immediate aftermath of the war. The hostilities began as irregular warfare between humanity and several remnant factions of the former Covenant, later seeing the involvement of Forerunner elements, specifically Promethean forces led by the renegade Ur-Didact, imprisoned millennia earlier by the Librarian, once humanity's greatest Forerunner supporter. This Forerunner aspect would come to define and greatly broaden the scope of the events, bridging directly into humanity's own prehistory and origins, both eras being intertwined with those of the Forerunners. Various Human rebel groups, which most had been dormant during the Human-Covenant War, re-emerged as a third party in the new conflicts, there was at least one Covenant faction that had joined them in their war against the UNSC, which had pre-dated their war with the Covenant.

In one of the first human-Covenant conflicts after the ceasefire at the end of the Covenant War, one of the Covenant splinter groups attacked the human colony of Draetheus V, seeking to obtain a powerful Forerunner weapon held there. In 2557, a reformed Covenant under the leadership of Jul 'Mdama gained access to the shield world of Requiem, home to the Didact, a legendary Forerunner Promethean whose aid the Covenant sought to enlist in their campaign against humanity. The ensuing series of skirmishes led to the Didact's release and an alliance between the Promethean forces and the Covenant, who revered the Didact as a "living god". Covenant forces subsequently helped the Didact retrieve the Composer, an ancient Forerunner device with the power to enslave mankind.

Although the Didact was later defeated by Spartan John-117, the Covenant continued to occupy Requiem and to search for the Librarian. They contested the UNSC for control of the shield world again in early 2558; the drawn-out battle eventually culminated in the installation's destruction but not the defeat of the Covenant, who had already withdrawn most of their forces from Requiem. After ONI attempted to assassinate her on Requiem, Dr. Catherine Halsey began to collaborate with Jul 'Mdama in order to recombine the cartographical artifact known as the Janus Key and unlock the Absolute Record.

Background

Historical context

"You and I are brothers in many ways... not least in that we faced the Didact before, and face him now, and perhaps ever after. This is combat eternal, enmity unslaked, unified by only one thing: our love for the elusive Lifeshaper. Without her, humans would have been extinguished many times over."

— 343 Guilty Spark to the crew of UNSC Rubicon

Humans and Forerunners battle during their millennium-long conflict.

While the final year of the Covenant War was marked by clashes for newfound Forerunner artifacts and the revelation of humanity's birthright as chosen inheritors to the Forerunner civilization, yet more significant discoveries would follow in the wake of the conflict. Long-hidden details about the Forerunners and their relationship between humanity began to surface, as did information regarding the yet more ancient and enigmatic race known as the Precursors. These unprecedented findings would have an immediate influence on events in the modern times, acting as driving forces for not only renascent Covenant cults but also forces far more ancient.

Before the Forerunners first built the Halo Array, the human race held a great interstellar empire. During the course of their growth as a civilization, they encountered a terrifying threat: an extragalactic parasite known as the Flood. As the parasite ravaged their worlds and threatened to consume their entire species, humanity fled outwards from their home territory. As they did so, they attacked any Forerunner world where an infection had taken hold, neglecting to warn the Forerunners of the threat in favor of bombarding infected areas immediately. Ignoring their warnings about the dangers posed by the Flood, the Forerunners – led by the Ur-Didact and his Promethean Warrior-Servants – defeated humanity and forcibly devolved their civilization. However, the Forerunners were left vulnerable by the long conflict: their military had been weakened, and all information regarding the mysterious threat that humanity had been fleeing was lost. After millennia of calm the Flood returned and the Forerunners were ill-prepared to fight back.

The Forerunner Builder rate had prepared for this eventuality, creating a number of ring-shaped superweapons known as the Halo Array. However, the Didact was reluctant to use these and instead planned to use the Composer, a device capable of transferring organic consciousness to software, as a means to save the galaxy's populace from Flood infection. But the process was flawed, and those who underwent the process were unable to be reconstituted to their organic forms. This, however, suited the Didact's purposes: he would use the Composer to convert his Prometheans into mechanical warriors, later augmenting their numbers with converted humans to create a massive army to fight the Flood. In his view, this was both an elegant solution to the Flood problem and a means of neutralizing the human threat forever. However, his wife the Librarian was horrified by his actions, and sealed him inside the shield world Requiem, which was his base of operations. The converted Prometheans were left there to guard his Cryptum, and Requiem remained quiet for millennia after the Forerunners were wiped out by the Halo Array.

Contemporary situation

"Decades from now, when historians evaluate the war, what will they say about us? Will they claim that our victory was ultimately fruitless? That it failed to secure a lasting peace, or worse, that it was only a prelude to far greater horrors that now lay ahead?"

— Codename: SURGEON prefacing the first Eleventh Hour report

The commissioning of UNSC Infinity

Although the death of the Prophet of Truth at the Ark during the endgame of the Covenant War saw the ultimate defeat of the Covenant and humanity's truce with the Sangheili species, it was not long after the end of the war that rogue splinter groups, many of them still hostile toward humanity, began to rise from among the remnants of the hegemony. With large amounts of former Covenant matériel at their disposal, it was inevitable that these disparate remnants would band together against their former enemy, against the best efforts of those who favored a policy of peaceful cooperation, an approach most visibly embodied by Arbiter Thel 'Vadam. Humanity's aggressive rearmament (largely made possible by the acquisition of Forerunner technologies and exemplified by the colossal warship UNSC Infinity as well as the rapid creation of hundreds of new Spartan supersoldiers) combined with the Office of Naval Intelligence's shortsighted approach to neutralize their former enemies, did little to ease the concerns of more hostile elements within Sangheili society.

The figure who would ultimately give a face for the new Covenant was a former Sangheili Shipmaster known as Jul 'Mdama. Although 'Mdama had always resented humanity (in particular their perceived virulent expansion and colonization) even in the wake of the human-Sangheili alliance, the ultimate catalyst for his quest against mankind came in the form of the death of his wife Raia, for which he blamed humanity due to their involvement in the Blooding Years. During his time in ONI captivity on ONIRF Trevelyan, 'Mdama had learned that the Didact, a mighty Forerunner general with a hatred for humans, was trapped inside a Forerunner world known as Requiem. After escaping Trevelyan, 'Mdama began to gather followers in order to travel to Requiem and unlock the world's secrets, intending to use the Didact as a motivating force for his followers, but also a new spiritual voice for his people and a chance to exact vengeance on humanity.

Humanity found itself facing renewed internecine struggle as well. While the Insurrection had ceased as a major conflict at the start of the Covenant War in 2525, some surviving colonies still harbored former Insurrectionists as well as individuals sympathetic to the cause of colonial secession. Some colonies, including Venezia, cut off all ties with the UEG under the pretense that Earth had abandoned them during the war. Some rebel groups managed to obtain large amounts of Covenant and UNSC weapons and equipment circulating on the black market.

Insurrectionist attack on Infinity

NCA forces attempt to capture UNSC Infinity.

Main article: Raid on UNSC Infinity

In January 2553, elements of the New Colonial Alliance led by UNSC defector Ilsa Zane (the only survivor of the SPARTAN-IV program's prototypical stage) infiltrated the UNSC Infinity disguised as construction personnel and captured most of the bridge crew, using them as hostages. They then secured the ship's bridge in the hope of capturing the prototype UNSC flagship, threatening to vent the ship's atmosphere and kill everyone aboard it. The attempt was foiled by the first team of SPARTAN-IVs (who had recently been brought aboard) and the insurgents were all killed or captured. The prisoners revealed Admiral Mattius Drake as the organization's leader.

Continuing Jiralhanae-Sanghieli hostility

Brutes Choppers raid Sangheili settlements.

Main article: Blooding Years

Though 'Vadam sought a lasting peace with humanity, many of the Sangheili were not willing to suddenly end their war with the humans. Many Sangheili insurgents, rallied together by the Servants of the Abiding Truth, incited war against the Arbiter and his allies for collaborating with humanity. Jul 'Mdama, a former member of the Servants of the Abiding Truth, eventually formed his own revival of the Covenant, with the Sangheili again serving as its leadership caste.

With Truth dead, High Charity destroyed, and the Ark heavily damaged after Installation 04B's firing, some of the remaining Jiralhanae forces tried to rebuild their tattered strength to continue their war of conquest. Even though the Jiralhanae eventually collapsed into various civil wars, they still posed enough of a threat that Sangheili commanders kept up the offensive against them for at least another six years, even as they continued to lose irreplaceable warships and the war continued with no end in sight.

The Covenant had strategically settled Jiralhanae populations on resource-rich worlds as a planetary garrison force to protect the worlds from potential raids. While the Jiralhanae continued to inhabit these worlds after the dissolution of the Covenant, they were unable to mine or utilize the resources because of their own lack of sufficient technology. With the Covenant's supply chains gone, the Jiralhanae quickly found their supplies near depletion. This was one of the primary reasons for their raids on Sangheili colonies after the war; despite quite literally living on top of plentiful resources, the Jiralhanae were entirely dependent on the already processed supplies of other races due to their technological backwardness. However, the Jiralhanae could not sustain themselves via raiding alone in the long term and their supplies began to wear thin, leading to an impending species-wide famine in 2558 and an increase in Jiralhanae attacks across Sangheili and Kig-Yar colonies as a result. During this crisis, the Jiralhanae Chieftain Lydus was willing to initiate peace talks with the Arbiter and the UNSC. However, the negotiations were interrupted by Covenant mercenaries hired by the New Colonial Alliance.

Sanghelios

Main article: Blooding Years

After the Human-Covenant war, many Sangheili still worshiped the Forerunners as gods. A religious sect known as the Servants of the Abiding Truth, led by war veteran Field Master Avu Med 'Telcam, took to believing that any tampering with Forerunner relics was heresy, just as most Sangheili did before the founding of the Covenant. As a result, 'Telcam and his followers grew angry with Arbiter Thel 'Vadam's government. After winning the favor of several keeps and mustering a small space fleet, the Servants led an uprising in the state of Vadam. They initially held the upper hand, but the tide turned when UNSC Infinity arrived and intervened on behalf of the Arbiter, shooting down a rebel destroyer and firing a MAC round into massing rebel ground forces besieging 'Vadam's keep. The ONI black operations team known as Kilo-Five, however, hoped to keep the planet destabilized for fear that the Sangheili would oppose humanity if they were politically unified, and so they used their prowler Port Stanley to destroy some of 'Vadam's cruisers. This caused a temporary stalemate, but the battle continued until 'Vadam and his allies emerged victorious. The Servants retreated off-world to New Llanelli to recover from their losses, putting the war on hold.

Pious Inquisitor

Main article: Skirmish on Pious Inquisitor

In March 2553, Kig-Yar pirate Sav Fel stole a CCS-class battlecruiser, the Pious Inquisitor, from the Servants of the Abiding Truth. Fel retreated with the battlecruiser to his manor on Venezia, where he sold it to Insurrectionist Staffan Sentzke, a commander in the Venezian militia, who intended to use it to threaten Earth to learn about his daughter's fate. The crew of Paragon—led by Shipmistress Chol Von—was hired by Avu Med 'Telcam to retrieve the vessel and arrived at the cruiser's location in April 2553, with Fel. While Von wish to capture Pious Inquisitor to use as a flagship in a united Kig-Yar navy, Kilo-Five intended to take control of the vessel and return it to Thel 'Vadam. Ultimately, Kilo-Five—along with Staffan—and the crew of Paragon both attempted to seize the battlecruiser at the same time and a skirmish occurred on the ship. During the firefight, Sometimes Sinks, the eccentric Huragok that served aboard Inquisitor, transitioned the ship to a location designated by Staffan. With eight of the Kig-Yar dead and Kilo-Five approaching the bridge, Von had her remaining crew detonate the ship's plasma torpedo reserves, choosing to destroy Pious Inquisitor over leaving it to the humans. Von and her remaining crew managed to escape in time, along with Kilo-Five. While Staffan and Sinks escaped in the Spirit with the slipspace drive that Sinks had installed earlier, the UNSC presumed Staffan dead and thus believed that the Venezian threat was neutralized as they no longer had the power to glass planets.

Blue Team's missions

Main article: Gao conflict

After Blue Team's return in UNSC-controlled territory following the end of the Covenant War in March 2553, the Office of Naval Intelligence assigned the Spartans —consisting of Fred-104, Kelly-087 and Linda-058— to new missions on the outer fringes of human-occupied territory to eliminate lingering pockets of the previous war. Along with the survivors from SPARTAN-III Team Saber, one of these missions involved protecting a UNSC research battalion on the planet Gao. The Spartan-IIs would continue such missions for many years, at least until their fateful reunion with John-117 on July 25, 2557. The nature of these missions remained highly classified. Blue Team field-tested a number of upgraded MJOLNIR Mark VI armors that would serve to establish components of the recently released GEN2 armor, utilized in parallel by Spartan-IVs.

Spartan Ops

Main article: Spartan (branch)

Following the Covenant War, a rising number of Spartan-IVs were also deployed to quell Covenant and Insurrectionist threats on human colonies and exotic worlds, as part of what is collectively referred to as the Spartan Ops program. These missions consisted in suppressing revolts, civil unrest and uprisings; assassinating insurrectionist leaders; exploring uncharted space and worlds; halting criminal activities; providing security to UNSC bases, ONI classified sites, colonies and civilian populations; and escorting scientific expeditions. Such Spartan deployments have been sent to Cascade, Talitsa, Terceira, Thales, Trevelyan, Installation 03, Gaenir Beta, Charion VI, and New Caracas. Several MJOLNIR [GEN2] armors have been field-tested in such operations. Spartan-III and Spartan-IV personnel have also been employed as part of the post-war Headhunters during classified missions.

Draetheus V

Merg Vol's Covenant fleet closes in on Draetheus V.

Main article: Battle of Draetheus V

In 2554, a Covenant fleet led by Merg Vol invaded the UNSC research colony Draetheus V and its moon, X50, in search of Forerunner relics, beginning a major battle which marked one of the first missions of the UNSC's recently formed Spartan branch. The battle saw significant losses on both sides and the planet itself was nearly destroyed by Vol's use of X50, which was in fact a Forerunner superweapon with the capability to destroy planets. The main hostilities concluded with Spartan Sarah Palmer killing Vol and sabotaging X50's main weapon, bringing the Covenant's quest to a halt. However, the Covenant returned when a looping Forerunner code began emanating from X50. After arriving at the source of the signal, Spartan Palmer discovered that the source was the remains of Spartan Edward Davis, who had died during the battle. The installation disintegrated Davis's corpse and encapsulated it in an unknown device, and with the help of a Pelican, Palmer took the remains of her comrade with her.

Alpha-Nine's missions

Main articles: Draco III rebellion, Mission to Talitsa

In the post-war era the ODST squad Alpha-Nine was deployed on a number of operations against resurgent Insurrectionist factions. In 2554, they were deployed to repulse a violent United Rebel Front takeover attempt on Draco III. Although the insurgents were defeated the ODST known as the Rookie was killed in action. In the following year the URF captured the Huragok Quick to Adjust and his human handler Sadie Endesha on Talitsa. The still-active members of Alpha-Nine—now Spartan-IVs—participated in a mission to rescue the captives and ultimately succeeded, though the operation saw Spartan Michael Crespo's defection and subsequent incarceration.

Attacks on Outer Colonies

Main article: Mission to Cleyell

Several of the more fanatical splinter factions have continued the practice of glassing human colonies after the end of the Covenant War. The colony of Cleyell fell victim to such an attack in 2556. The UNSC Cascadia moved into orbit of Cleyell weeks later to deploy Army and Marine search-and-rescue teams to relieve the stranded colonists on the surface.

Sedra and Alpha Shard

Main articles: Terrorist attack on Sedra City, Mission to Alpha Shard

Sedra City being affected by a bioweapon.

On February 7, 2556, the capital city of the human Outer Colony of Sedra was targeted by a Sangheili terrorist, who unleashed a powerful bioweapon that randomly broke down human DNA. A subsequent ONI investigation revealed that the substance used to create the bioweapon originated from a surviving fragment of Installation 04, propelled through slipspace into orbit around a red giant star. The ONI unit, led by Lt. Commander Jameson Locke, were forced to cooperate with the Sedran Colonial Guard on a mission to capture the smugglers who mined the element and destroy the deposits with a HAVOK tactical nuclear weapon. However, what was to be a swift operation quickly turned into a desperate battle for survival after the group was attacked by Lekgolo swarms that resided on the Halo fragment. The mission ended with the destruction of the bioweapon's deposits, but at the expense of the lives of almost all the joint team, including the former SPARTAN-II Randall-037, with Lt. Commander Locke and Private Talitha Macer being the only survivors.

Return of the Forerunners

"Time was your ally, but now it has abandoned you. The Forerunners have returned."

— The Didact

Requiem

The Didact immobilizes John-117.

Main article: Battle of Requiem

By 2554, Jul 'Mdama had already gathered formidable numbers of followers and a powerful fleet which discovered Requiem, but were unable to enter the thoroughly sealed shield world. In orbit above the planet, however, was the wreckage of the Template:UNSCship, carrying the legendary Master Chief, SPARTAN John-117, and his deteriorating AI companion Cortana, drifting in space since the end of the Covenant War in 2552. Upon discovering the derelict vessel in July 2557, 'Mdama's Covenant forces attacked the Dawn in hopes of deterring any potential efforts by the humans to access the shield world. During the ensuing skirmish, Requiem's automated systems pulled both the Dawn and the Covenant force surrounding it through the world's outer shell and down to the planet's surface.

On Requiem, both John-117 and the Covenant forces that hunted him were attacked by the mechanical Promethean forces that occupied the structure. In the core of the installation, the Master Chief accidentally released the Ur-Didact from his millennia-long imprisonment. Bent on preventing mankind from attaining the Mantle, the Didact departed the core and allied with 'Mdama's Covenant. Meanwhile, UNSC Infinity, lured to Requiem by Forward Unto Dawn's distress signal, crash-landed inside the shield world. Making way for the crash site, the Master Chief reunited with the UNSC and aided in the defense of the stranded flagship from the Covenant and the Didact. However, due to a difference of opinion between Infinity's captain Del Rio and John-117, the latter was left facing the Didact alongside Cortana while Infinity returned to Earth.

The Composer

Main article: Raid on Ivanoff Station

The Didact left Requiem on his flagship Mantle's Approach, intent on acquiring the Composer, a Forerunner device with the power to enslave all of humanity. With John-117 and Cortana in pursuit, the Didact attacked Ivanoff Station, a UNSC research facility near Installation 03 and the location of the Composer. Despite the UNSC's best efforts, the Didact was able to acquire the Composer and used the device on the occupants of the station, but John-117 was saved by enhancements provided by the Librarian's personality construct back on Requiem.

Battle over Earth

The Composer firing on New Phoenix.

Main article: New Phoenix Incident

The Didact then headed for Earth with the Master Chief acing across the hull of Mantle's Approach aboard an F-41 Broadsword fighter. With support from Infinity and the UNSC Home Fleet, John-117 made his way inside Mantle's Approach and confronted the Didact, but not before the Forerunner used the Composer to digitize the population of New Phoenix, URNA. With the aid of a rampant Cortana, the Master Chief was able to send the Didact plummeting into the Composer's slipspace rupture and destroy his ship with a HAVOK nuclear warhead. Using the last of her power, Cortana was able to translocate John away from the blast, saving his life at the cost of her own. Left adrift in space, he was later recovered and brought aboard Infinity and debriefed by the UNSC Security Council shortly afterward.

The Didact fell through the slipspace portal to the surface of Installation 03, where he quickly recovered and killed Spartan Black Team and a UNSC science team. Meeting with the monitor 859 Static Carillon, the Promethean commander then entered the Composer's Forge via a portal, intending to continue his crusade against humankind.

The Conduit

Main articles: Battle of Installation 03, Battle of New Phoenix

The Composer's Forge

The battle at the Composer's Forge

Main article: Skirmish on Installation 03

Due to the loss of contact with the science team on Gamma Halo, Fleet Admiral Terrence Hood sent Blue Team, consisting of Fred-104, John-117, Kelly-087, and Linda-058, to investigate. Upon their arrival at Installation 03, Blue Team found the corpses of the scientists as well as Team Black. They soon discovered the Composer's Abyss and a portal leading to the Composer's Forge, an installation housing six new Composers. There they encountered the Didact and his new batch of Promethean constructs. During the ensuing firefight, Static Carillon transported Installation 03 above the Composer's Forge per the Didact's request. The Didact acquired one of the Composers in the Forge and departed for Gamma Halo with the plan to use the ring to wipe out humanity. However, the monitor sided with the Spartans and helped them defeat the Didact due to his abhorrence of the Promethean machines.

After surviving another clash with the Didact on Installation 03, John-117 confronted the Didact in the control room while the rest of his team returned to their Longsword fighter. The Master Chief used the Activation Index to disable the Halo's safety protocols, allowing Static Carillon to eject the entire plate section housing the control room. The segment fell on the Composer's Forge, destroying the Composers housed there. The resulting explosion overwhelmed the control room and reduced the Ur-Didact to ashes.

Static Carillon teleported John-117 out of the control center in time and bade farewell to the Spartans before taking Gamma Halo to an undisclosed location. Blue Team returned to Earth where the Master Chief was debriefed by Fleet Admiral Hood. Afterward, John and Blue Team departed to carry out missions on their own in spite of Lord Hood's suggestion that the Master Chief should stand down.

Return to Requiem

UNSC forces accessing Requiem.

Main article: Requiem Campaign

While the Didact was seemingly quelled, proving a setback for the Promethean-Covenant alliance, it did not result in their defeat. Six months later, in February 2558, Infinity returned to Requiem with a fresh complement of Spartans, determined to conquer the planet at any cost with the intent of studying the Forerunner relics therein. In the interim, Requiem had been occupied by Jul 'Mdama, who now held sway over the local Promethean armies. The Covenant ships in orbit around the planet were swiftly defeated and scattered, demonstrating the technological advancement of the UNSC since the end of the last war.

Significant numbers of UNSC military forces were deployed on Requiem, including detachments of Spartan, Marine, Navy, Air Force and Army forces on Requiem. Arriving on the planet's surface, Majestic, Crimson and other SPARTAN-IV squads began to disrupt Covenant operations across Requiem and recover Forerunner artifacts for study. The Covenant in turn made numerous attempts to destroy Infinity while also trying to gain access to the stored memories of the Forerunner known as the Librarian.

The campaign ultimately ended in Requiem's destruction when Jul 'Mdama set the planetoid on a collision course with the sun. Both sides evacuated the doomed system, each possessing their own half of the Janus Key. After ONI's failed attempt on her life Dr. Catherine Halsey was convinced that the UNSC was working against her and agreed to work with Jul 'Mdama to accomplish her personal goal of reuniting the halves of the Janus Key to unlock the Absolute Record.

New Colonial Alliance

UNSC Infinity is ambushed by Daniel Clayton

Ealen IV

Main article: Battle of Ealen IV

By March 2558, Jiralhanae raiding attacks along the Joint Occupation Zones had significantly escalated due to the Jiralhanae's lack of supplies. Nonetheless, Lydus, the Chieftain of a Jiralhanae master-pack, agreed to enter peace negotiations with Arbiter Thel 'Vadam. Ealen IV was chosen as a place for the negotiations, mediated by the UNSC's Fleet Admiral Terrence Hood. However, the delegates were attacked by Covenant mercenaries under the command of Shipmaster Vata 'Gajat. Captain Thomas Lasky and the delegation's SPARTAN-IV security detail, consisting of Fireteams Jackknife and Bailey, were forced to defend and evacuate the ambassadors. The Spartans eventually managed to evacuate the delegates and Vata 'Gajat was forced to retreat, though it came at the cost of many Spartans, including Paul DeMarco.

The events revealed a significant security breach in the UNSC, with Spartan Vladimir Scruggs exposed as a traitor along with the implicit presence of a higher-ranking leak within the organization. The Covenant's attack itself was a major setback to Thel 'Vadam's efforts to make peace with the Jiralhanae. Captain Lasky later discovered that the attack on Ealen IV had not been orchestrated by the Covenant remnants, but by Daniel Clayton, a UNSC captain and defector to the New Colonial Alliance bent on revenge against Lord Hood, who hired Vata 'Gajat and his troops to stage the attack.

Infinity ambushed

Main article: Ambush at Oth Lodon

After their failed assault on Ealen IV, 'Gajat and Captain Clayton lured Admiral Hood and the UNSC Infinity into a trap using a freighter, the Pilgrims' Pride which sent out a distress signal that was later picked up by Infinity. An ambush was sprung when the freighter set itself to self-destruct after being towed into one of Infinity's main bays and launched multiple automated craft that engaged the UNSC forces. The attack was repelled by the SPARTAN-IVs of Infinity.

After the ambush, the Infinity crew discovered that the assault crafts aboard the Pilgrims' Pride were from the long-lost UNSC Spirit of Fire. With the Spirit's possible location found, Lord Hood authorized Palmer to conduct a search-and-rescue in Oth Lodon's system. However, Captain Clayton launched a surprise attack against the UNSC flagship using a Covenant battle station's energy projector. The strike disabled Infinity, but Commander Palmer and Fireteam Majestic were able to seize the NCA station. They also destroyed 'Gajat's ship, which was preparing to attack Infinity, killing the mercenary leader.

Many members of the Infinity crew were killed in the attack, including Commander Bradley, while Fleet Admiral Hood was left paralyzed. Captain Clayton was detained in Midnight Facility while Infinity remained under repair for a month.

Bioweapon incident

Main article: Mission to Ven III

A Covenant force on Ven III.

By 2558, Ven III had become a hot spot for numerous Kig-Yar smugglers, black market arm dealers, and slavers. When FLEETCOM ignored the Office of Naval Intelligence's requests to assault the pirate base, ONI devised a false-flag operation involving a biological agent purportedly stolen by a Sangheili agent of Jul 'Mdama—in truth a mercenary hired by ONI—to force the Fleet to take action. Admiral Osman tasked Captain Lasky of Infinity with capturing the Sangheili and recovering the bioweapon before it could threaten human colonies. Lasky selected Spartans Gabriel Thorne and Naiya Ray for the mission and they were deployed on Ven III. After Thorne was captured and Ray discovered the pirate hideout Lasky decided to involve Infinity in the mission and engaged the pirates in space and in their stronghold. Spartan Ray rescued Thorne and chased down the Sangheili agent but ONI personnel forced Ray to stand down and took the Sangheili into custody.

The Janus Key and the Absolute Record

The Infinity under attack by Jul 'Mdama's fleet on Aktis IV.

Attack on Oban

Main article: Battle of Oban

In July 16, 2558, 'Mdama's forces and his Promethean allies attacked the human colony of Oban. The attack was repelled by a joint Spartan-UNSC Marine operation, resulting in substantial casualties on 'Mdama's side. However, the true goal of the attack had been to enable Dr. Catherine Halsey—still collaborating with 'Mdama—to establish a connection between to Infinity's slipspace engine, preventing them from jumping into slipspace. This was part of a plan to force the crew of Infinity to hand over their half of the Janus Key and allowing Halsey to unlock the Absolute Record.

Ambush on Aktis IV

Main article: Battle of Aktis IV

As part of their plan to reunite the halves of the Janus Key, Halsey and 'Mdama created a decoy Forerunner artifact that was seemingly compatible with the Key. The artifact was placed in a Forerunner structure on the uncharted planet Aktis IV along with a fake signal to draw Infinity to investigate. 'Mdama placed his troops on standby, ready to ambush the UNSC forces once they brought their half of the Janus Key to the planet. The crew of Infinity acted just as Halsey and 'Mdama had predicted, sending their half to the surface for analysis; however, Sali 'Nyon, a rebel among 'Mdama's ranks, shot the Pelican carrying the artifact down before 'Mdama had given the signal to attack and took the Key for himself. With the ambush botched, 'Mdama's concealed forces revealed themselves and attacked both Infinity and the Spartans at the Forerunner site, while Jul departed to the planet to personally eliminate the rebels and reacquire the Janus Key.

The conflict continued for over seven hours, with Infinity engaged by 'Mdama's fleet while Sali 'Nyon's rebellion raged on in the Covenant's ranks. One member of 'Nyon's faction grew disillusioned with the rebellion, stole 'Nyon's Janus Key half, and offered it to 'Mdama's forces. Dr. Halsey, escorted by 'Mdama's Sangheili, traveled to the planet to reclaim the Key. Meanwhile, the Spartans in the Forerunner structure managed to use the local teleportation grid to travel to the surface, splitting into two groups with different destinations. Commander Palmer's team spotted the Sangheili defector with the Janus Key and upon overhearing his intentions, she decided to ambush Halsey once she arrived. Palmer successfully captured Halsey but the doctor managed to cloud the Spartan's judgment and escape with the Janus Key. 'Mdama successfully eradicated all of Sali 'Nyon's followers on Aktis IV, ending the rebellion. Jul had Halsey retrieved and the two recombined the halves of the Janus Key, revealing the location of the Absolute Record. After the Spartans returned to Infinity, Commander Palmer told Captain Lasky that the UNSC had to prepare for the worst with the Janus Key in 'Mdama's possession.

Hunting the Master Chief

Raid on Biko

John-117 during the Raid on Biko.

Main article: Raid on Biko peace talks

After years of diplomatic work, peace talks were finally scheduled between humanity's Unified Earth Government and the Sangheili. The convocation was held in a regional embassy in a densely populated city on Biko in the human Outer Colonies. Richard Sekibo, the revered ambassador of the Outer Colonies, led the conference.

Sekibo had uncovered evidence of a terrorist plot by Sapien Sunrise one week before the attack. He petitioned the UNSC for help, but they rejected his request immediately.

As the conference was coming to an end, an agreement of peace was close to being reached. Suddenly, rogue Spartan-II John-117 entered the embassy and instantly killed Richard Sekibo's bodyguard, who in reality were Sapien Sunrise infiltrators. A firefight began, in which John abducted Sekibo and created an escape path through the infiltrators by killing them. John fled the embassy alongside the Sangheili delegation, which he escorted to safety.

Outside the embassy, an evacuation ship for John was waiting. He boarded the ship, alongside the alien diplomats, and fled the planet. At some point, Sekibo was killed and his corpse was left behind in a field near the embassy on Biko. The next day, local officials discovered a signal beacon that led them to the body of Sekibo.

Battle of Sunaion

Main article: Battle of Sunaion

Following the disappearence of MCPO John-117 and subsequent abrupt attacks on several colony worlds, Lieutenant Commander Jameson Locke was tasked with tracking the rogue Spartan down and returning him to the United Nations Space Command. To this end, Locke met with Arbiter Thel 'Vadam and asked for his assistance in tracking down the rogue Spartan. Seeking the Master Chief, the Swords of Sanghelios and Fireteam Osiris took part in a joint operation to capture Jul 'Mdama's resurrected Covenant's last bastion on Sanghelios: Sunaion.

As the Swords of Sanghelios began their voracious assault on Sunaion, Locke's team inserted via Lich into the city and searched for traces of the Master Chief. After finding traces of John-117, a Guardian appeared and took position near the city, with Blue Team entering the construct. At this point, Fireteam Osiris encountered the Warden Eternal, who claimed that they were not allowed passage to access the nearby Guardian.

List of appearances

• Halo: The Thursday War (First appearance)
• Halo 4
  • Spartan Ops
• Halo: Spartan Assault
• Halo: Initiation
• Halo: Escalation
• Halo: Mortal Dictata
• Halo: Nightfall
• Halo: New Blood
• Halo: Spartan Strike
• Hunt the Truth
• Halo: Hunters in the Dark
• Halo: Last Light
• Halo 5: Guardians