2553

2553 was a year in the Military Calendar.

Background
2553 was one of the bloodiest years in the Human-Covenant War, as well as the last.

It saw the Human and Separatist victory of the Great War over the Covenant Loyalists. As well as the full destruction of Gravemind-lead Flood forces, and his death. It is unknown if the Loyalists have been disbanded or were completely destroyed at the Battle of Installation 00.

Second Battle of Earth
At the beginning of the year, Covenant Loyalist forces assaulted the Human city of Cleveland, Ohio in the United States on Earth. The Loyalists were looking for the Key of Osanalan, a mysterious Forerunner device related to the Halo Installations.

Later during the Second Battle of Earth, a battle at Pawas in Afghanistan took place. There, UNSC Marine Corps forces battled Loyalist forces for control of a Satellite installation. Numerous Marines of the 2nd ODST Battalion targeted the Forerunner Dreadnought entering Earth's atmosphere. Onboard was one of the last SPARTAN-II Commandos, Master Chief Petty Officer John-117.

Battle for Kenya
During the Battle for Earth, the Crow's Nest was an Underground Facility used by the UNSC Defense Force to coordinate local Army, Navy, and Marine forces.

Shortly after John-117's arrival in Kenya, Loyalist forces attacked the facility in force, supported by a CCS-class Battlecruiser orbiting above the savannah.

SPARTAN-117, SgtMaj Avery Johnson, the Arbiter, GySgt Pete Stacker, and GySgt Reynolds then organized a defense of the base. First, they attacked infantry in a large roadway containing numerous supply trucks and armament. Then, they engaged one of the bases hangars in control by Jiralhanae forces, with support by Type-52 "Phantom" Troop Carriers. When they took control of that hangar, it allowed Marines to escape from the base.

Soon after the short skirmishes, they detonated a large bomb in the Operations Center, effectively destroying the base and all enemy forces within it.

The Battle of Voi was the last battle in the long and bloody Second Battle of Earth.

The Prophet of Truth's fleet of twenty-eight CCS-class Battlecruisers and two Assault Carriers led by Truth in the Forerunner Dreadnought had committed all their forces to Africa, specifically Voi, Kenya and the surrounding regions.

At Kenya, Brute-led Covenant infantry and vehicular detachments overwhelmed ground-based UNSC defending forces while Truth's cruisers deployed to Voi, glassing a savanna in pursuit of a presumed Forerunner artifact hidden underground there, presumed to be the Ark.

SPARTAN-117 led a UNSC counterattack to regain lost UNSC ground, retaking a jungle near Mount Kilimanjaro and securing the area around the Crow's Nest. Commander Miranda Keyes and Sergeant Major Avery J. Johnson then organized a small UNSC strike force led by SPARTAN-117 to attack the Covenant Loyalist-held Tsavo Highway, and thus have a platform for a strike at Voi.

The UNSC Marine Corps was able to retake the Tsavo Highway, and it served for a staging ground for the battalion that would retake Voi. The UNSC forces stationed already at Voi had already suffered severe casualties, with only pockets of Marines drawn in a scattered last defense against numerically superior and vehicularly-supported Loyalist forces.

Fleet Admiral Sir Terrence Hood declared that it was imperative that SPARTAN-117's attack force retake Voi. Lord Hood's plan was that he would launch a low-level aerial strike on Truth's fleet above the Forerunner artifact, and prevent him from activating the presumed Ark. However, a Loyalist anti-aircraft emplacement stationed at Voi prevented Hood fleet from advancing; SPARTAN-117 was to retake Voi and destroy the anti-aircraft emplacement to allow Hood to attack Truth's fleet, and prevent him from activating the Ark.

They later defeated the AA guns, opening up a pocket in the Loyalist Defenses for the Home Fleet to come in and engage Truth's forces. They were successful in damaging the Dreadnought, though it was allowed to escape through the Portal.

Flood on Earth
The victorious UNSC forces were now encountering unknown hostiles all over the Town and the splintered and weary forces were no match. The Flood had found their way to Earth and begun to infect and spread.

Commander Keyes gave a single order, which was to fight to the core of the ship and overload its reactors, destroying the ship and the town and any Flood along with it.

The Sangheili Fleet of Retribution, had followed the Flood infected ship from their blockade at Installation 05 to its arrival at Earth. They began to drop forces to push towards the ship, seeking a prize that lay within it. It wasn't until they came back into Traxus Facility that the Sangheili told the UNSC. Cortana, the AI formally attached to the Spartan-IIs, the and companion of John-117 was upon that downed ship.

The joint UNSC/Separatist force pressed on, still giving their all to getting to the crash site. They eventually broke through, fighting past Flood Pure Forms. With the remaining forces giving cover to the Chief, he entered its Floodformed carcass and retrieved Cortana. After the ground forces were evacuated safely the Elites began to glass the immediate area, annihilating any chance of further Flood infection, effectively ending the Battle of Voi.

Battle of Installation 00
The Prophet of Truth, having successfully activated the artifact in Kenya, left Earth through a Slipspace portal to the Ark, a Forerunner structure that can be used to fire all of the Halo installations at once.

Despite Lord Hood's urging, Commander Keyes took ships from the Home Fleet with a small fleet of Separatist cruisers lead by the carrier Shadow of Intent and proceeded through the Slipspace portal and arrived at the Ark.

The Separatists on arrival immediately engaged the Loyalist fleet stationed to protect the Prophet while the Dawn deployed Marine Shock Troopers to locate Truth. Despite being outnumbered 3-to-1 in space, the Separatist fleet made short work of the Loyalist space forces, likely due to the Elites' superior tactical skills. The Covenant Loyalist Fleet had been destroyed and the only Loyalists left alive were Truth and his forces on the Ark. 343 Guilty Spark, now working with the UNSC-Separatist Alliance, led SPARTAN-117 and the Arbiter to the Ark's Cartographer where they pinpoint the Prophet's location. By then Truth had already holed himself in a secure facility in the core of the Ark and had activated a large barrier around the entire core to ward off the attacking forces.

The UNSC ground forces, along with Separatist reinforcements, assaulted three emitter pylons that powered a small section of the barrier. When the defending forces were eliminated and the pylons shut down, the Shadow of Intent began its attack on Truth. At the same time the former Covenant city ship High Charity arrived from Slipspace and crashed on the Ark. Debris spread from the city ship heavily damaged the Shadow of Intent and helped spread a new Flood infestation on the Ark as a means to stop Truth and to be safe from the Halo activation array. Without any heavy support, SPARTAN-117 and the Arbiter personally attacked the facility where Truth was to activate the Halo installations.

Sergeant Major Johnson, who had disappeared during the assault, was in fact captured by Truth's forces and was being tortured into pressing the final switch to activate the other Halos. With SPARTAN-117 and the Arbiter too far away to stop Truth, Commander Keyes grabbed a Pelican dropship and crashed into the facility to rescue Johnson, but was killed soon after by Truth himself. The Gravemind dispatched Flood forces to assist SPARTAN-117 and the Arbiter in preventing the Halos' activation and the Arbiter personally killed Truth. However, the Gravemind betrayed them and while Johnson managed to escape with Commander Keyes' body in the Pelican, SPARTAN-117 and the Arbiter had to fight their way outside.

Elimination of the Flood
343 Guilty Spark had managed to facilitate the making of a new Halo through the Ark, explaining that a tactical pulse from it would eliminate the Flood infestation. However, this new Halo lacked an Activation Index. The only way they could get another Index was to rescue Cortana from High Charity since she still possessed the Index from Installation 04. Through a tough battle, SPARTAN-117 and the Arbiter successfully entered the ruins of High Charity and recovered Cortana, using a partly-damaged Pelican to escape while High Charity was destroyed as its reactors went critical after the Spartan blasted them.

End of the War
With the Index secure, the Arbiter ordered that the remaining UNSC forces relocate to the Separatist ships and escape back through the Slipspace portal to Earth while he, SPARTAN-117 and Sergeant Major Johnson moved in on the Control Room of the incomplete Halo. The Dawn was left behind for them to use to escape. By now what was left of the Gravemind had relocated to the new Halo. The three heroes with 343 Guilty Spark made it through waves of Flood to the Control Room. 343 Guilty Spark explained that the new Halo would be ready to fire within days, but with Flood moving in all around them Johnson wanted to fire the ring now. When Guilty Spark protested that activating Halo now would destroy both the Ark and the installation, Johnson told him to "deal with it" and prepared to activate the ring.

Unwilling to let "his" ring be destroyed again, Spark went rampant, killing Johnson and attacking SPARTAN-117 and the Arbiter. However, by the help of a dying Johnson and his laser, SPARTAN-117 managed to destroy Guilty Spark and start the firing sequence for the new Halo. They escaped the control room by taking Johnson's Warthog to the Forward Unto Dawn.

However, the Slipspace portal collapsed as the Dawn entered it and while the forward half with the Arbiter made it to Earth, the rear half fell out of Slipspace with Cortana and SPARTAN-117 becoming missing in action.

With Truth dead, the Halos deactivated, and the Flood destroyed, the Battle of the Ark ended the Human-Covenant (Separatists) War. A monument was erected in the Kenyan Savannah in remembrance of those who gave their lives in the war including SPARTAN-117 who is labeled MIA. The Arbiter and his surviving brethren departed Earth for their homeworld, Sanghelios.

United Nations Space Command

 * Commander Miranda Keyes
 * Sergeant Major Avery Johnson

Covenant Loyalists

 * High Prophet of Truth

Forerunners

 * 343 Guilty Spark

Flood

 * Gravemind

Battles

 * Battle of Mare Erythraeum
 * Second Battle of Earth
 * Battle of Cleveland
 * Battle of Pawas
 * Battle of the Crow's Nest
 * Battle of Voi
 * Second Battle of Mombasa
 * Battle of Installation 00
 * Second Battle of High Charity