Halo Alpha
Halo Alpha

“We shall cut into the heart of this infestation, retrieve the Icon, and burn any Flood that stand in our way!”

One of the battles of the 9th Age of Reclamation, the Battle of the Quarantine Zone was a rare battle in which all four of the main factions took part. The Covenant and UNSC fought through the Quarantine Zone in search of the Activation Index, known to the Covenant as the Sacred Icon. Both parties had to battle their way through legions of Flood and Forerunner machines designed to halt the parasitic outbreak.


Not much is known of how the battle of the Quarantine Zone began, as it is rooted in ancient history. The Battle began after an unknown event, approximately 100,000 years ago, when the Flood under containment on Installation 05 were released.[2] Under normal circumstances Sentinel guards would have been able to keep the parasite under control. Unfortunately, the Flood had access to hosts, and were able to hold off the constructs.

After building enough biomass, a local Proto-Gravemind reached critical mass, allowing the formation of a sentient, highly aware form of flood stage known as the Gravemind. Now coordinated, the Flood posed a serious threat. The battle soon spiraled out of control, and Sentinel Constructor Factories were built to construct more powerful constructs, such as Sentinel Majors and Enforcers. An enormous wall was built around the Installation's Library, which was housing the Gravemind.[3] The area within the boundaries of the wall were starved of heat and light in order to inhibit Flood growth, and thus the Quarantine Zone was established.

Over the centuries, the Gravemind's reach spread throughout the Installation.[4] The Monitor of the installation, 2401 Penitent Tangent was captured by the Gravemind, giving him access to the Teleportation Grid,[3] and causing the structures on the Installation to fall into disrepair.

The Battle[]

The Human Mission[]

Inadvertently arriving at Installation 05 after following a Covenant ship, one of Commander Miranda Keyes' primary goals was the capture of the Forerunner activation key; the Index. To know exactly what she was up against, she accessed all information (classified or not) to do with the rings from AI Cortana.

While John-117 was busy on a special mission to assassinate the High Prophet of Regret, many of the In Amber Clad's Marines and the ODST contingent; along with many of the Pelicans, were called back to take part in the mission.

Breaching the outer wall with ease, over 200 Marines led by Keyes and Sergeant Major Johnson entered the second wall through multiple spots. With the shield down temporarily, the UNSC In Amber Clad was brought into the Quarantine Zone to provide support.

Ill prepared against the Flood,[notes 1] Marine groups started to come under attack by the Flood. Many of them were not even briefed on the Flood's existence.[notes 2] Many of the Marine teams were quickly overrun and infected. The newly formed Human Combat Forms then moved to attack the remaining human teams. Many running gunbattles occurred as the Marines continued on towards the Index with the Flood in close pursuit.

Escaping the wall defenses, the remaining Marines were welcomed by the arrival of reinforcements. Although armed with the In Amber Clad's remaining supply of tanks and warthogs, UNSC superiority was short-lived.[notes 3] Reaching a large-sized gondola designed to take them to the Library interior, only half a dozen Marines remained to accompany Keyes and Johnson.

By the time they began their gondola ride, the Flood had not only captured or shot down their Pelicans, but had begun an assault on the In Amber Clad. While the few remaining Marines fought in the structure, the ship was overrun by the Flood. Now with an FTL-capable vessel at hand, the Flood's objective was accomplished.

Covenant intervention[]

“Once the shield is down, we'll head straight to the Library. I do not wish to keep the Hierarchs waiting.”
— Tartarus to Thel 'Vadamee.[5]

The Covenant began their own attempt to seize the Index with a landing party of Brutes, Grunts, and Jackals. Immediately after landing on the outer wall, the party was attacked by Sentinels. The Covenant troops began fighting a long, bloody engagement as Sentinels began coming out of multiple ports in the walls along most of the corridors the Covenant team had to walk through. Suffering heavy casualties and under constant attack, the team began having stragglers but continued on. By the time the Covenant warriors had reached the end of the outer wall, only 6 Brutes and 4 Grunts remained. These last ten Covenant then encountered a Sentinel Enforcer. Attempting to flank the Enforcer failed, as it bombarded the party with pulse beams and missiles, killing the Covenant soldiers even when they tried to take cover. A Grunt Major managed to escape the firefight, however the Brutes and the rest of the Grunts were killed.[5]

H2A Enforcer

An Enforcer about to ambush the Arbiter.

With most of the landing party killed and the survivors scattered and surrounded, the Arbiter of the Covenant was sent to the surface of the ring to retrieve the Index. Dropped directly into the outer wall by a Phantom where the landing party had started, the Arbiter followed the path of destruction from the earlier battle and rallied the surviving members of the original landing party (3 Grunt Majors and 2 Jackal Majors). The Arbiter and his team reached the Enforcer and this time the Covenant managed to destroy it and lower the shield around the Index. Traveling across to the second wall, the Covenant soldiers learned that Human Marines had made it through the wall first, only to be swiftly infected by the Flood. By lowering the Containment shields, the Covenant allowed more free movement for the Flood. More Covenant warriors soon entered the Quarantine Zone along with their own vehicular support, unfortunately exacerbating the Flood outbreak. The Arbiter and his team were transported right into the middle of a skirmish between Sentinels and infected Marines. The soldiers with the Arbiter were finally killed but he managed to get inside the second wall and fought his way along the same path a 20-man team of Marines had tried to take before the Flood killed them.[5]

The breach of containment led to the rapid growth in the Flood's numbers. Large numbers of Covenant troops and commandos supported by Wraiths and Ghosts landed in the Quarantine Zone, with many being quickly killed and infected. The remaining Marines from the In Amber Clad, supported by 4 Scorpion tanks, 2 Gauss Warthogs, and 3 Warthogs, suffered a similar fate. With these new hosts, the Flood gained access to more sophisticated equipment, weapons and combat vehicles, magnifying the danger the outbreak presented immeasurably. The Flood showed a bit of a tactical genius by shooting down one of the Forerunner Sentinel Constructor ships.

Despite the large outbreak, Covenant and Human forces were able to battle their way through the legions of Flood and Sentinel constructs. Elements of both parties eventually reached the Gondola entrance points to the Library of Delta Halo. Commander Miranda Keyes, Sgt. Johnson and 6 Marines entered the Library first. They were quickly followed by the Arbiter and a squad of 4 Sangheili SpecOps troops. Rtas 'Vadumee stayed behind to defend the Gondola station.[1]

The Library[]

“A bloody fate awaits you and the rest of your incompetent race. And I, Tartarus, Chieftain of the Brutes will send you to it!”
— Tartarus to Thel 'Vadamee.[1]

Human forces had gained access to the Library first, but only by a matter of minutes. Upon arrival within the Library the humans were attacked by Flood Combat Forms and a Phantom piloted by Tartarus and his Brutes. All the humans except Keyes and Johnson were killed.[notes 4]

Keyes Tartarus

Tartarus and a captured Keyes.

The Arbiter found Miranda Keyes and Sergeant Johnson within the Index Chamber, having retrieved the Index seconds before his arrival. Sergeant Johnson was ready, armed with a Battle Rifle, along with Miranda Keyes who was reaching for the Index holding on to one of the Gravemind's tentacles. Miranda secured the Index and drew two SMGs. Johnson called for his last two Marines, but received no answer and armed his weapon. The Arbiter proved his worth as a warrior once again, incapacitating both Johnson and Keyes in a matter of moments. The arrival of Tartarus within the Chamber signified the beginning of the Civil War of the Covenant as he attacked the Arbiter, sending him plummeting to his death deep within the Library, towards the Gravemind.[1]


Some of the Marines and ODSTs, such as Gunnery Sergeant Marcus P. Stacker and Staff Sergeant Marcus Banks managed to survive the Flood outbreak. However they and some of the Marines in their commands were captured by the Covenant. The human prisoners were split up, with some staying on Halo and others being put into multiple detention facilities on High Charity.

The battle itself from a religious point of view, was a strategic victory won by the Covenant for they achieved their objective which was to retrieve the Index and were able to capture the humans necessary. Tactically however, the Flood were the victors as they succeeded in not only escaping Installation 05 but gained the means to spread to other worlds via infestation of any ships that came. The UNSC forces, however, failed to recover the Index and were almost completely killed or infected by the Flood.


There is supporting evidence to entail and suggest that the Marines were never attacked by Sentinels but were in fact assisted by them. This is not out of the question because, like on Installation 04, the Sentinels might have identified the Marines as Reclaimers, rather than how Sentinels branded the Humans as an "Aboriginal Subspecies" on Onyx. This would also explain their open hostility to the Covenant who were enemies of the Humans.

For starters, the Arbiter encounters an enormous and massive number of Human Combat Forms inside the Sentinel Wall immediately after he deactivates the shield. This suggests that the humans had been deployed much earlier which should have been impossible. First of all, the marines should not have been able to deploy immediately after the barrier went down because In Amber Clad would've first had to slip past the Covenant forces that were moving in to secure the inner wall. However, if the Sentinels had chosen to assist the marines, they would've deactivated a small portion of the barrier to let them in. Also, in the area where the UNSC Pelican flies over head, there are a number of Sentinels and even an Enforcer present. None of which seem to show any hostility towards the Pelican. Another factor is simply that considering how much trouble Covenant Elites had getting inside the Library, it doesn't seem likely that the marines would've been able to get past the Flood and the Sentinels. However, if the Sentinels had been helping them, then it's much more likely that they would've succeeded.


Halo 2[]

Halo 2: Anniversary[]



  1. Evident by the presence of Magnum sidearms near corpses
  2. "Negative, Ma'am, they are not Covenant."
  3. Evident by the un-appearance of Marine-controlled vehicles. By the time the Arbiter and his Elites arrived, the Flood had captured most of the human vehicles and infected or killed the Marines operating them.
  4. Evident by the non-appearance of other Marines in the Quarantine Zone ending cutscene, and the presence of six Marine corpses nearby.


  1. 1.0 1.1 1.2 1.3 Halo 2 - Level: Quarantine Zone
  2. Halo 3 - Promotional Material: Cold Storage Transmissions
  3. 3.0 3.1 Halo 2 - Level: Gravemind
  4. Halo 2 - Level: Regret
  5. 5.0 5.1 5.2 Halo 2 - Level: Sacred Icon