2553

2553 was the first year that saw relative peace for humanity and the some of the disparate member species of the collapsed Covenant following the twenty-eight years of interstellar war.

January

 * Dr. Ruth Charet gives her inaugural address after her election as President of the Unified Earth Government.
 * Jun-A266 visits Sarah Palmer in the Lockhart medical station to recruit her into the nascent SPARTAN-IV program.
 * January 7: The first class of the SPARTAN-IV program, consisting of 145 volunteers, is initiated.
 * A New Colonial Alliance strike force led by Ilsa Zane infiltrates UNSC Infinity and briefly commandeers the new UNSC flagship before the attack is driven back by the newly-created SPARTAN-IVs aboard the ship.
 * January 26: The black ops cell Kilo-Five is formed by CINCONI, Admiral Margaret Parangosky. Its members include Captain Serin Osman, Naomi-010, and several ODSTs. Because of Parangosky's distrust of the Sangheili, she sends Kilo-Five on a mission to cause insurrection between the Swords of Sanghelios led by Thel 'Vadam and the Servants of the Abiding Truth.
 * January 27: Kilo-Five depart for their first mission aboard.
 * The UNSC Security Council begins the reconstruction of the colonies. Lord Hood plans a diplomatic mission to surviving UEG colonies to discuss plans for reconstruction.
 * Kilo-Five supplies arms to the Servants of Abiding Truth on New Llanelli in the Brunel system.
 * Kilo-Five retrieves ONI spy Mike Spenser from a UNSC listening post on Reynes.
 * Commander Musa-096 holds a meeting of several admirals at HIGHCOM Facility Bravo-6 to discuss the creation of the SPARTAN-IV program and the Spartans as their own military branch.
 * January 31: Dr. William Arthur Iqbal sends a message to his colleagues concerning the ongoing study of Forerunner artifacts.

February

 * Lord Hood arrives at Sanghelios to meet with Thel 'Vadam to formalize a treaty of peace between the humans and the Sangheili. Hood also invites Thel to attend the memorial ceremony dedicated to those who died during the war.
 * After Lucy-B091 discovers a population of Huragok within Shield World 006, the Huragok assist the human survivors in establishing communications with the ONI ships prowling the debris field of Onyx. The Huragok soon bring the shield world into normal space from the slipspace bubble, thus allowing the ONI vessels to retrieve Dr. Catherine Halsey, SCPO Franklin Mendez and the SPARTAN-IIs and SPARTAN-IIIs of Blue Team. Per an order from Admiral Parangosky, Dr. Halsey is arrested by Captain Serin Osman.
 * ONI dispatches science teams to recover Forerunner technologies from the shield world, designating the sphere as ONI Research Facility Trevelyan at Dr. Halsey's request.
 * Jul 'Mdama is captured by Kilo-Five and is transported to ONIRF Trevelyan.
 * February 28: Shadow of Intent remains stationed on Earth for a diplomatic mission.

March

 * Andrew Del Rio is chosen as the commanding officer of the experimental vessel.
 * March 3: In a ceremony presided over by Lord Hood, a monument is erected in the Kenyan savannah near Mount Kilimanjaro to officially mark the end of the Human-Covenant War, and in remembrance of those who gave their lives in the war, including John-117, who is labeled MIA and is (presumably) posthumously promoted to Master Chief Petty Officer of the Navy. A full military detail, led by Gunnery Sergeant Stacker and including PFC Chips Dubbo, deliver a three volley salute to the fallen. All the remaining SPARTAN-II super-soldiers are present for the ceremony. After the ceremony, Thel 'Vadam and his comrades depart Earth for their homeworld, Sanghelios.
 * Dr. Catherine Halsey is interrogated by Admiral Margaret Parangosky at Ivanoff Station.
 * Evan Phillips is assigned on an intelligence-gathering mission on Sanghelios.
 * Kilo-Five travel to the Insurrectionist-controlled colony Venezia and meet with the local ONI contact, Mike Spenser.
 * Insurgent attacks, carried out by Jiralhanae servants, result in the death of dozens of Sangheili in Ontom on Sanghelios. During the attack, Evan Phillips and a fragment of Black-Box make their way into the Temple of the Abiding Truth. Eventually, Phillips activates a translocation portal within the structure and is transported to Acroli.
 * Kilo-Five arrive at Sanghelios to retrieve Phillips. Upon failing to find Phillips in Ontom, they track him down to Acroli, specifically the Nes'alun Keep, under attack by forces from the nearby Lacalu Keep. Phillips is rescued while the Sangheili in the keep are killed by the invaders.
 * is installed further Forerunner upgrades, most notably the ship's slipspace drive, by Dr. Catherine Halsey and a number of Huragok recovered from ONIRF Trevelyan.
 * Forces loyal to the Servants of the Abiding Truth launch an assault on Vadam, starting the Sangheili civil war. This attack is eventually repelled by the arrival of UNSC Infinity. During the orbital battle between 'Vadam's forces and the Sangheili insurgents, Jul 'Mdama's wife, Raia 'Mdama, is killed.
 * Jul 'Mdama escapes captivity on Trevelyan via a slipspace portal. He is transported to Hesduros, where he is welcomed by the local Sangheili as a messenger of the gods. Jul plans to use the locals' religious devotion to his own advantage, banding them together to form a new splinter group of Covenant.

April
April 5 April 12-13
 * Kilo-Five return to Venezia in order to continue their mission of tracking down the Kig-Yar pirate Sav Fel and the terrorist Staffan Sentzke.
 * Serin Osman is promoted to Rear Admiral and a small party is held aboard Port Stanley in her honor by Kilo-Five.
 * Sav Fel sells the Covenant battlecruiser Pious Inquisitor to Staffan Sentzke, who intends to use the ship to force UEG authorities to provide answers about the disappearance of his daughter.
 * Vasily Beloi and Malcolm Geffen infiltrate the Venezian militia in order to gather information about Sentzke and Pious Inquisitor. Following a series of suspicious incidents, Sentzke begins to doubt the ODSTs' cover story of deserters and has them captured and tortured. However, Naomi-010 and Lian Devereaux eventually arrive and successfully extract Mal and Vaz. During the rescue, Sentzke is also taken captive aboard Port Stanley.
 * A Kig-Yar crew led by Shipmistress Chol Von track down and board Pious Inquisitor with the intent of seizing the ship for themselves.
 * Kilo-Five board Pious Inquisitor and a skirmish occurs between them and the Kig-Yar. Chol Von eventually has her crew destroy the ship. Staffan Sentzke is presumed dead in the ensuing explosion, but he actually manages to escape without ONI's knowledge.

May

 * The Ordnance Commission, headed by the major defense companies and sponsored by ONI, establishes several conditions on the use of MJOLNIR GEN2 variants.

August

 * Spartans Lucy-B091 and Tom-B292 (serving under the Spartan branch) are assigned to a classified location.

September

 * The status of Spartans Ash-G099, Olivia-G291, and Mark-G313 is changed from missing in action to killed in action.

November

 * A pioneer group arrives at Reach to prepare for the planet's eventual reterraforming, an undertaking that would be well underway by 2589.

Unknown date

 * Gabriel Thorne's grandfather dies.