Battle of Requiem

The Requiem campaign was a series of large-scale battles and small skirmishes on the Forerunner shield world Requiem. It was waged between the Prometheans and their Covenant religious followers and the intruding UNSC Defense Force. These engagements marked the beginning of the Human-Promethean war on July 20, 2557. The days following would see the conflict spread to Installation 03 and the human homeworld, Earth. The campaign would be resumed in February 2558 when the UNSCDF launched a lightning-strike expedition to the surface of Requiem.

Background
In December 2552, the aft half of the, carrying Spartan John-117 and AI Cortana, was transported via slipspace on a course toward Requiem after the last battle of the Human-Covenant War. Cortana activated Forward Unto Dawn's emergency locator beacon while the Spartan entered cryostasis. Within the next year, Jul 'Mdama led his forces, a partly reunited offshoot of the Covenant, to Requiem in search of the shield world's "treasure": he sought the Didact, the leader of the Forerunner military, due to their mutual hatred of humanity. However, 'Mdama could not find a way into Requiem, so the fleet held station in orbit.In July 2557, the Dawn entered the planet's gravity well; 'Mdama sent his forces to board the frigate to keep any humans away. As Covenant troops entered the ship, Requiem began to scan the Dawn for a "Reclaimer".

Opening skirmishes
Cortana awoke John-117 from cryostasis and informed him of intruders on the Forward Unto Dawn. When the duo found out that there was a Covenant fleet around the Dawn and one of the s was moving into a intercept course, Cortana instructed John to fire one of Dawn's missiles at the cruiser. The Spartan battled through the wreckage and managed to destroy the cruiser moments before it fired its energy projector. While on the outer hull, John was scanned by a beam coming from Requiem, which then opened its interior for the Reclaimer. Forward Unto Dawn, along with several Covenant cruisers, was pulled into Requiem's interior.

John-117 and Cortana survived the fall into Requiem's middle shell. They decided to hijack one of the surviving Covenant ships to return to Earth, where they would be able to find Dr. Catherine Halsey to assess Cortana's rampancy. However, had picked up Forward Unto Dawn's distress beacon and was approaching the shield world. While looking for a way to contact Infinity, John and Cortana accidentally triggered Requiem's guardians, the Prometheans. The Prometheans attacked the Spartan as well as the Covenant. In an effort the warn Infinity of Requiem's gravity well, the Spartan-AI team disabled two energy pylons inside Requiem's core in order to eliminate interference emitted from a satellite in the core. When John attempted to contact Infinity in the satellite, it was revealed that the Didact had purposely manipulated Infinity ' s signal to trick John-117 into releasing him from his Cryptum. The Didact openly declared war on humanity and reassumed control of his mechanized Prometheans; viewing the Didact as a living god, the Covenant forces followed suit. John escaped Requiem's core just as Infinity entered Requiem's outer shell.

Infinity ' s arrival
Infinity crashed into a jungle inside Requiem and was immediately attacked by Promethean and Covenant forces. During the attack, Infinity 's commanding officer, Captain Andrew Del Rio, deployed Marines and SPARTAN-IVs for reconnaissance, believing that the Infinity would be able to fend off her attackers while providing support for ground forces. The ill-prepared Marines were overwhelmed by the unfamiliar Prometheans and suffered heavy casualties. In addition to losing their landing zones, many Pelican dropships were shot down. Infinity was eventually boarded, allowing the Didact to extract information about the Composer, a Forerunner superweapon, from the ship's mainframe. John-117 joined Commanders Thomas Lasky and Sarah Palmer just as Captain Del Rio recalled ground forces to Infinity. John cleared a landing zone for the UNSC forces and headed to Infinity 's crash site. There, John-117 and a squad of SPARTAN-IVs broke through to one of Infinity 's hangar bays. John piloted a Mantis assault mech and fought through Infinity 's maintenance corridors to some of the ship's weapon systems. After John destroyed the Covenant jammers near the control terminals, Infinity disabled two CRS-class light cruisers and damaged the Didact's Cryptum, prompting the Forerunner to retreat. The repaired Infinity left her crash site, but since she was still under the effect of the Requiem's gravity well, Captain Del Rio sent John-117 and Gypsy Company to take down the Forerunner anti-air particle cannons near the gravity well generator.

Assault on the gravity well generator
Gypsy Company, aboard a Mammoth and led by Commander Lasky, destroyed the first and second anti-air particle cannons. However, a Covenant Lich heavily damaged the Mammoth. Even though John-117 and a SPARTAN-IV team destroyed the Lich, the Mammoth was forced to stop when it approached a Forerunner structure.

John entered the structure and, with Cortana's help, disabled the last two anti-air cannons. Cortana suddenly disappeared, so John searched the structure for her. He was taken to an archived personality of the Librarian, the Didact's wife and the one who saved humanity from the Halos. The Librarian informed John of the Didact's plan to imprison humanity into digital form with the Composer. In doing so, she altered John-117's genes, an action that would prove itself useful when the Didact's forces raided Ivanoff Station. John-117 returned to a UNSC convoy led by Master Sergeant Marcus Stacker and eventually reached Requiem's gravity well generator. Using targeting data provided by the Spartan, Infinity destroyed the generator.

The Didact's departure
Despite their explanation, Del Rio was skeptical, dismissing it as hallucinations from John’s age and Cortana’s rampancy. When he ordered the Infinity to return to Earth, Cortana gave a short outburst of rage followed by John leaving to stop the Didact alone. Departing from the ship with a Pelican gunship given to them by Lasky, the Chief set out to stop the Forerunner, almost succeeding but failing; the Didact managed to regain his ship, the Mantle's Approach and promptly left for Ivanoff Station to retrieve the Composer. He was followed by a fleet of Covenant Liches and the Master Chief who stowed away aboard one.

Infinity ' s return
In February 2558, UNSC Infinity returned to Requiem. s were deployed to protect the ship and establish a position in orbit. Spartan-IV fireteams were sent into Requiem to support the UNSC Marine Corps, Armies and Air forces. UNSC forces set up several research bases: Copernicus Base, Galileo Base, and Magma Base. Other locations, such as areas designated "Quarry", "Fortress'', and "Apex", were often contested for control.

During an interception on a Covenant archaeological dig, Fireteam Crimson discovered one of the three Requiem translocation artifacts on Requiem in "the Cauldron". The artifact was brought onboard Infinity, where it was examined Henry Glassman. Glassman, who accidentally activated it, was translocated to Requiem and became a prisoner of the Covenant remnant. There, he was brought to Jul 'Mdama and was forced to find a method to activate the device containing the Librarian AI. Captain Lasky requested Doctor Catherine Halsey to be brought onboard Infinity to study the translocation artifact. Halsey found out that the artifact was communicating with the ship's system's, notably the engine, and transmitting signal to a location in Requiem. On Requiem, Sangheili Parg Vol, an associate of 'Mdama, was hunted and eventually assassinated by Fireteam Crimson.

Jul 'Mdama's Plan
During their flight to Copernicus Base, Fireteam Castle was shot down by Covenant forces led by Jul 'Mdama. This attack drew Infinity 's attention to hunt down 'Mdama. UNSC scientists have discovered that the Covenant remnant are using Requiem's portal systems, and Fireteam Crimson was deployed to assist in the investigation. Incidentally, 'Mdama was detected traversing through the portals, so Fireteam Majestic and Crimson were sent to give chase. After discovering a way to activate Requiem's portal systems, Crimson followed 'Mdama to "the Cauldron", where he purposely left an artifact known as the "Didact's Gift" for Crimson, prompting the team to bring the artifact to Galileo Base.

The Covenant remnant then staged an attack on the base to show that they were attempting to recover the artifact. While Fireteam Crimson defended the base, Fireteam Majestic extracted the "Didact's Gift" and brought it back to Infinity, where it was analyzed by Halsey. By giving Halsey the "soul of a Promethean Knight", 'Mdama had gained Halsey's interest in cooperating to find the Librarian. Their partnership, however, was discovered by Captain Lasky and Commander Palmer, who then took Halsey into custody. Spartan Gabriel Thorne, during his examination of the translocation artifact, was taken to Requiem like Glassman. On Requiem, the Covenant and Promethean forces attacked UNSC research bases "the Refuge" and Magma Base, but both of these attacks were successfully repelled by Fireteam Crimson (with the assistance of Fireteam Shadow in "the Refuge"). During their search for Spartan Gabriel Thorne in "Quarry", members of Crimson were captured by Covenant forces.

Spartan Thorne was captured by the Covenant and was brought to where Glassman was. Glassman, on the other hand, managed to activate the Librarian's device, and used the opportunity to escape. Glassman's escape distracted the Sangheili who took Thorne prisoner, giving Thorne the chance to retaliate. Together, the duo ran away, heading for Galileo Base.

List of appearances

 * The Commissioning
 * Halo 4