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February
February 6
 * Gabriel Thorne becomes a member of the SPARTAN-IV program and is assigned to the Fireteam Majestic.

February 8
 * returns to Requiem to establish research facilities on the shield world. Commander Sarah Palmer, leader of the Infinity ' s Spartan contingent, sends various Spartan teams, notably Fireteam Crimson and Fireteam Majestic, to the surface of Requiem. Marine, Army, and Navy assets are also deployed.

Unknown date
 * Spartan Fireteam Crimson uncover a Forerunner slipspace artifact. After the device teleports Chief Engineer Henry Glassman to the surface of the planet, Dr. Catherine Halsey is brought in to investigate.
 * The artifact scans the ship's systems and begins transmitting data to the surface of Requiem, where said data is intercepted by Jul 'Mdama. Glassman is taken captive by the Covenant and is ordered to activate the Librarian's shrine, though he is not successful.
 * Sangheili terrorist Parg Vol is assassinated by Fireteam Crimson.
 * Fireteam Crimson secure another Forerunner artifact, dubbed "the Didact's Gift". This device contains the memories of victims of the Didact's attack on New Phoenix six months prior. The processed human minds are to be repurposed as Promethean Knights. Spartan Gabriel Thorne is translocated to the Cauldron by the first artifact.
 * Dr. Halsey begins dialog with an unknown party who shares her interest in the Librarian. The intelligence is actually Jul 'Mdama, the Covenant's leader, who is manipulating Halsey into divulging vital secrets about the Forerunners. Halsey is apprehended after her unwitting communication with 'Mdama is discovered. Spartan Thorne rescues Dr. Glassman and the pair escape custody.
 * Dr. Halsey learns that John-117 is still alive. The Infinity is boarded by Covenant and Promethean forces who capture the doctor. They take her to the Librarian's "shrine", where 'Mdama awaits.
 * Gek 'Lhar, 'Mdama's lieutenant, is killed by Fireteam Majestic.
 * Admiral Serin Osman, head of the Office of Naval Intelligence, orders Captain Thomas Lasky to kill Dr. Halsey. Commander Palmer is to execute the order.
 * Lasky sends Fireteam Majestic to rescue Dr. Halsey and stop Palmer.
 * The Librarian gives Dr. Halsey the Janus Key, but Jul 'Mdama gets half of the key. Halsey gives Gabriel Thorne the other half before she is taken away.
 * Jul 'Mdama sends Requiem on a collision course with its sun, Epoloch. While the shield world is destroyed, the UNSC Infinity narrowly escapes the planet's slipspace conduit.
 * Dr. Halsey agrees to cooperate with Jul 'Mdama and his forces, stating that she wants revenge.

March
March 3 March 5
 * Captain Lasky and Commander Palmer are debriefed by the UNSC Security Council at HIGHCOM Facility Bravo-6. The committee expresses misgivings of Lasky's handling of the Second Battle of Requiem and the failed assassination and escape of Dr. Halsey. Admiral Hood later tasks Infinity to escort him and the Arbiter on a diplomatic mission to Ealen IV.
 * Battle of Ealen IV: Infinity arrives at Ealen IV. Lord Hood meets with Thel 'Vadam and the Jiralhanae Chieftain Lydus. While negotiating, the delegates come under attack from Covenant mercenaries working for a group of human insurgents. The SPARTAN-IVs defend the ambassadors, who escape into a nearby parts depot.
 * Shipmaster Vata 'Gajat arrives on Ealen IV to personally oversee the attack, while the ambassadors escape through a series of tunnels leading to a fortified redoubt in which they could take refuge in. Captain Thomas Lasky orders Commander Palmer and the protection detail to escort the delegation to the redoubt, while he and Spartan Ray try to reestablish communications with the fleet above the planet.
 * As Fireteam Jackknife arrive at the redoubt, Vladimir Scruggs betrays his own team, killing them and the bodyguards. He then informs Commander Palmer it is safe to bring the delegates into the redoubt.
 * In orbit, the Sangheili and Jiralhanae ships begin to deploy forces against each other due to the ambiguity of the situation on the ground.
 * Lasky and Ray destroy the reactor generating the Covenant jamming signal, restoring communications.
 * After the ambassadors and their security detail arrive in the redoubt, Scruggs ambushes them and holds Hood at gunpoint. Palmer shoots Hood in the leg and, in the resulting confusion, confronts and kills Scruggs.
 * With the Covenant bearing on the site in force, the ambassadors escape to Infinity aboard a Covenant cargo tug. Paul DeMarco and Fireteam Bailey sacrifice themselves to cover the ambassadors' escape with Tyrant AA guns.
 * Infinity rallies the Sangheili and Jiralhanae fleets, prompting 'Gajat's fleet to retreat.
 * A funeral ceremony is held for the Spartans fallen in the battle, the practice of listing Spartans KIAs as MIA having been abolished.

March 8
 * Lasky and Hood discuss the likelihood of a severe security breach in the UNSC's organization, surmising that Scruggs could not have been the one who leaked the location of the negotiations.
 * Lasky and Hood discuss enlisting Petra Janecek's help in rooting out the spy who betrayed the Ealen IV delegation; the Fleet Admiral is uneasy with Lasky's decision due to a conflict between Hood and Janecek.
 * Lasky and Ray leave the Infinity in a prowler in order to recruit Janecek.

March 10
 * Lasky and Ray meet with Janecek in Castiglione on Escala III. Petra agrees to help Lasky uncover the UNSC spy in return for information regarding the Master Chief.

March 11
 * The Infinity is ambushed on a mission to rescue a damaged civilian freighter, Pilgrims Pride. However, they come under attack by automated craft supposedly originating from the long-lost.

Unknown dates
 * Petra Janecek, Captain Lasky and Spartan Ray travel to the Sangheili colony of Karava to uncover the identity of the UNSC traitor. Meeting Janecek's informant Zef 'Trahl, they learn that the traitor is Daniel Clayton, former UNSC captain and the illegitimate son of Spirit of Fire's commanding officer, Captain James Cutter.
 * The UNSC supposedly discover the whereabouts of Spirit of Fire using data from Pilgrims Pride. Infinity sets out to rescue the older ship. Upon arrival at the Spirit's supposed coordinates near Oth Lodon, however, they find a Covenant battlestation manned by the New Colonial Alliance. Having lured Infinity into a trap, Captain Daniel Clayton fires on the UNSC vessel with the station's enormous energy projector.

April

 * Eight months after the attack on New Phoenix, the city is lifted from its quarantine. Spartan Gabriel Thorne returns to his hometown in search of answers.