Human-Covenant war

The Human-Covenant War, also known as The Great War, was a major interstellar conflict between the United Nations Space Command and the Covenant during the mid-26th century.

The conflict was closely connected with, and the cause of, the Covenant Civil War; both of which proved instrumental in the final defeat of the Covenant and Flood on March 3, 2553.

Background
Humanity and the Covenant first came into direct contact in 2525, (twenty-seven years before the events of Halo: Combat Evolved), when the Covenant attacked the UNSC Outer Colony world Harvest. The Covenant had been covertly studying the human race for some time prior to that, as they had knowledge of the English language as well as the location of at least some human worlds. After several encounters (Including the Covenant's raiding of several UNSC supply ships and a minor skirmish between Nolan Bryne, and Avery Johnson and four Jackals), the UNSC and Covenant officially met on Harvest in a diplomatic meeting (although the Covenant was only interested in owning the planet due to the number of Forerunner artifacts within it). The meeting was botched after Osmo, a member of the Colonial Militia, was attacked by a nervous Grunt and a firefight erupted.

The Prophets declared humanity to be an affront to their gods (supposedly because humans inhabited and 'defiled' areas which were once Forerunner), and called for a crusade against the Human species. An extended, though one-sided, ground battle took place on Harvest and the Covenant eventually used their capital ships' plasma weaponry to vaporize the surface of the planet, turning the crust into molten glass, a process which would become known as "glassing."

From that point on, the Covenant continued to attack and destroy the humans wherever they were found. Though the UNSC forces fought bravely, their inferior technology and numbers meant that even a close victory was far from guaranteed. The Covenant also had an advantage in that they didn't need to fight planet-side to destroy the enemy; their ships simply needed to destroy the humans' space-borne defenses and any other threats planet-side, and then reduce the planet's surface to glass with orbital plasma bombardments. The few victories achieved by the UNSC were due to special tactical maneuvers, as human missile, and magnetic acceleration weapons were unable to compete with Covenant energy shields and plasma torpedoes. Over twenty-seven years, the Covenant whittled down the UNSC planet by planet. On Sigma Octanus IV, the Covenant were defeated but placed a Spy Probe on the, which led the Covenant to the UNSC's stronghold and main headquarters, Reach. The battle that followed had staggering losses for both sides, but ended in a pyrrhic Covenant victory. The was among the surviving UNSC ships which fled the battle, and made a blind jump to the Forerunner ringworld of Halo, chased by a dozen Covenant ships.

The Covenant's first truly costly defeat was on and around Halo. Here, the human survivors from the Halcyon-class cruiser, the Pillar of Autumn, managed to form an effective resistance. Unwilling to risk damaging the sacred ring, the Covenant was forced to fight the humans on Halo's surface rather than using its usual bombardment tactics. The Covenant found the Humans uncannily adapted to Halo's environment and very adept at fighting on the surface, with Human firearms and vehicles proving effective despite their technological inferiority. Unable to counter the guerilla tactics employed by the humans and the unexpected emergence of The Flood, the Covenant was soundly defeated in numerous raids, including one instance when the humans boarded their grounded cruiser, the Truth and Reconciliation, and successfully escaped with a group of captives, including the captain of the Pillar of Autumn, Captain Jacob Keyes. During the course of the battle, the human known as the Master Chief discovered the true nature of Halo and proceeded to destroy the ring and escape, much to the Covenant's horrified dismay.

According to the novel Halo: First Strike, shortly after the defeat at Halo, the Covenant had amassed a large fleet that appeared to be intended to assault Earth. It is explained in the audio drama, ilovebees, that the Covenant discovery of Earth was an accident after the Pious Flea had been intercepted by the UNSC stealth ship Apocalypso. After retrieving a Forerunner artifact, the Apocalypso made a Slipspace jump directly to Earth. When the ship tumbled into real space and crashed on the moon, the Pious Flea sent a message to the heart of the Covenant military, containing recon data, photos, starmaps, and the coordinates to the Forerunner Artifact, which is now on Earth. The events of Halo 2 apparently contradict the novel in explicitly stating that the Covenant had not identified Earth as the Human homeworld. However, the Unyielding Hierophant's fleet was never expressly identified to be intending to assault Earth; this is merely a reasonable assumption made by the human forces upon discovery of the fleet's destination of Sol. This leaves the exact nature of the fleet's mission uncertain, as there is no definitive proof that the Covenant were intending to attack a human homeworld. The surviving humans, however, believed this fleet to be a direct threat to Earth, and, using a captured Covenant flagship, lured the fleet into a trap and destroyed it.

A few weeks after this defeat, the High Prophet of Regret led a small fleet of fifteen ships to Earth, supposedly in order to locate a Forerunner artifact known as the "Ark." Though hopelessly outgunned by the UNSC's new orbital defense grid, the Prophet of Regret's flagship managed to break through the human defenses to New Mombasa. The Covenant ground troops quickly spread through the city, destroying both military and civilian resistance, but a counterattack by the Marines and the Master Chief drove them back. His fleet having been destroyed in orbit when he landed, Regret was forced to retreat. His carrier jumped into Slipspace from within the city, destroying it and clearing the area for a later Covenant excavation of the Ark.

Unfortunately for Regret, a single Human ship, the In Amber Clad, had followed them through their own Slipspace rupture to Delta Halo. With the orders "Find out why he came to Earth; why he came here," the Master Chief was hard-dropped with a compliment of Orbital Drop Shock Troopers to Delta Halo's surface. Led by the Chief, the Humans forced their way through Regret's forces until they had reached the Prophet himself. At that moment, High Charity, having learned of Delta Halo, arrived and launched multiple waves of Phantom dropships to aid Regret, but they were too late. The Chief assaulted and killed Regret, and the Covenant fleet recalled the Phantoms in favor of bombarding the area. It would seem they succeeded in "killing" Master Chief by burning away the building, as he came inches away from getting incinerated by the massive plasma beam glassing the area, plummeting down into the lake below.

Meanwhile, the majority of the human forces on In Amber Clad had travelled to Delta Halo's Library to obtain the Index, the key to firing Halo. Originally, the Covenant had been unaware of the Index's importance, but luckily for them, the Arbiter had obtained the Monitor of the first Halo while destroying a heretical sect. The Monitor, known to the Covenant as an Oracle, told the Prophets of the Index and the Arbiter was sent to retrieve it. The mission was complicated though by the unexpected release of the Flood. Despite this, the Arbiter successfully reached the Library and prevented the humans from claiming the Index. Just as Miranda Keyes claimed the index, the Arbiter stole it from her, kidnapping her and Sgt. Johnson. However, then Index was stolen from the Arbiter by the Brute Chieftain Tartarus, who under the Prophets' orders then attempted to kill the Arbiter. With the Index secure, the Prophets then ordered the Brutes to begin eradicating the Elites, thus starting the Covenant Civil War.

Following the Flood infestation of High Charity at the end of Halo 2, the High Prophet of Truth led the remaining loyalist fleet to Earth to complete what the previous mission to Earth had not. Little did he know that Spartan 117, Master Chief, had stowed away with him. By the time Truth arrived at Earth, a full-scale war in space and on the ground was underway between UNSC and Covenant fleets. After much fighting, the human forces were almost decimated, with their fleet almost completely destroyed and the entire human population reduced to a mere 200 million. However, the Covenant fleet was also vastly reduced and focused on securing an enormous unearthed Forrunner structure near the ruins of New Mombassa. With the arrival of Master Chief, the humans launched an assault on the area, sweeping aside covenant resistance and finally launching an all-out attack on the Prophet of Truth's Forrunner ship. However, Truth quickly activated a large portal and escaped. Events were further complicated by an unexpected attack by the Flood. With help from the Elites, the Flood force was vanquished, but not before Master Chief recovered a recording from Cortana, who had stayed behind on High Charity. Cortana's message told of a means to stop the Flood on the other end of the portal. A small fleet of Human and Elite forces was sent through the portal, leading them to the ark, just outside the Milky Way galaxy! The Covenant fleet above the Ark immediately attacked. Though the Human/Elite fleet was outnumbered 3-1, the battle ended in defeat for the Covenant. During the space battle, human forces were deployed to the surface of the Ark. The final battle of the war was fought on March 3rd, 2553, as Truth attempted to activate the halo rings. Led by the Master Chief, the human forces smashed through the remaining Covenant resistance. The battle was complicated by the arrival of High Charity. As the Flood began to spread, the Chief and the Arbiter went on to thwart Truth, who died in mid-flood-infection by the Arbiter's hand. With the Covenant forces completely shattered, Truth's death marked the effective end to the war.

United Nations Space Command
Leaders: HIGHCOM

Homeworld: Earth (largely intact at the end of the war, with the exception of a section of eastern Africa which was glassed)

Military Forces: Exact numbers are unknown.

The Covenant
Leaders: The High Council

Homeworld: multiple worlds

Capital City: High Charity (destroyed by the Master Chief after it was turned into a Flood Hive and crashed on the Ark)

Military Forces: Exact numbers are unknown.

2525

 * The Prophet of Truth discovers humanity's relation to the Forerunners, and instead of risking a bloody civil war that this knowledge could cause, he immediately demands the annihilation of all humanity.
 * The UNSC makes first contact with the Covenant at the UNSC colony world Harvest. The Covenant destroy the colony without warning or provocation.
 * The Battle of Chi Ceti takes place.

2530

 * The Covenant destroys the UNSC colony world of Eridanus II.

2531

 * Battle of Harvest. The UNSC and Covenant meet in ship-to-ship combat for the first time; the Covenant are outnumbered and outgunned, nevertheless the battle is a close victory for the Humans.

2535

 * The Covenant destroys the UNSC colony world of Jericho VII in the Battle of Jericho VII.
 * In the course of four short years, UNSC forces have been hammered, despite excellent leadership and tactical brilliance. It is simply a matter of being outgunned; Covenant kill ratios tend to top three to one in ship-to-ship combat. By 2535, virtually all of the Outer Colony worlds have been glassed by the Covenant.

2536

 * Covenant forces begin to swarm into the Inner Colonies. For several years the war falls into a pattern: humans win isolated battles, typically during ground operations, but at a horrible cost. In space combat, the humans are losing at a precipitous rate, and one by one, the colonies fall.

2537

 * Battle of New Harmony
 * Battle of New Constantinople
 * Siege of the Atlas Moons
 * Operation: PROMETHEUS: Pyrrhic UNSC Victory. Spartan-III Alpha Company is killed by Covenant forces

2544

 * The Battle of Miridem

2545

 * Operation: TORPEDO: Pyrrhic UNSC Victory. All but 2 of Spartan-III Beta Company is killed by Covenant forces

2549

 * Siege of Paris IV

July

 * Battle of Sigma Octanus IV. The single greatest UNSC victory since Harvest. However, the Covenant gain what they seek: the location of Installation 04. They also discover the human presence on Reach.

August

 * First Battle of Reach. 314 Covenant ships destroy 152 UNSC ships and 20 ODPs for the loss of at least two-thirds of their fleet. It is a major Covenant victory: Reach is the last major stronghold before Sol. The escapes.

September
*Battle of Installation 04. The Pillar of Autumn engages the Covenant Halo expedition. After four days the battledegenerated into a four-way melee as the Flood organisms are released and Forerunner constructs seek to contain the outbreak. The crew of the Pillar of Autumn are instrumental in preventing the Flood from escaping and the installation from firing by destroying the installation. There are only a handful of survivors.
 * Operation: FIRST STRIKE. Six SPARTAN-II supersoldiers rout and destroy a fleet of 500 Covenant starships preparing to jump to Earth. This is the single greatest victory for the humans during the entire war and the single greatest loss to the Covenant.

October

 * First Battle of Earth. 15 Covenant ships assault Earth, defended by 75 UNSC vessels and 300 ODPs. The Covenant were not expecting the heavy human presence, and are repulsed with heavy losses.
 * Battle of Installation 05. The lone surviving Covenant warship from the First Battle of Earth retreats to Installation 05, pursued by a score of small UNSC warships. Only one, the, arrives in time to participate in the battle. Again, released Flood and Forerunner overseers join the struggle. The Prophet of Regret is assassinated by SPARTAN-117. Again, the installation is prevented from firing and the Flood appear to take control of the installation.
 * The Civil War of the Covenant begins. Covenant forces are thoroughly divided between the Elites and the Brutes. Every race in the Covenant takes sides. The Prophet of Mercy is later killed by a Flood Infection Form. High Charity itself is eventually overrun by the Flood infestation.
 * Second Battle of Earth. The Brute faction of the Covenant returns to Earth in force, apparently conquering Africa. Later, during the next months the Marines, with help of the Separatists, pushed back the loyalist invaders.

November

 * Battle of Onyx. The destruction of Installation 04 wake dormant Forerunner installations, including the sentinels on Onyx which then threaten the UNSC base there. SPARTAN-IIs of Blue Team fight there way off Earth and commandeer a Covenant Destroyer, the Bloodied Spirit, to relieve Onyx. Covenant and UNSC ships converge on Onyx but ultimately all are destroyed except for the . UNSC survivors retreat within the Onyx Shield World.
 * Battle of Installation 00
 * All Loyalist vessels destroyed over the Ark by the Seperatist Fleet
 * The final Covenant religious leader, the Prophet of Truth, is executed by The Arbiter with help from the Flood. The Master Chief stops the Ark from firing the Halo Rings.
 * High Charity is destroyed by the Master Chief after he blasts the city's main reactors causing them to go critical.
 * The Second Battle of Installation 04. The Arbiter, Master Chief and Johnson battle to the control room that's on Installation 04 (II). Guilty Spark runs rampant, killing Johnson before being destroyed. Alpha Halo’s sentinels turned on the Master Chief, Johnson, the Arbiter, and the Elites. The unfinished Installation 4 is activated, damaging the Ark and destroying the entire local Flood infestation. These final events ended The Great War.

March 3

 * The war ends in a UNSC-Covenant Separatist victory. The victors erect a monument on a hillside near the Ark's Gateway to commemorate those fallen. At this time John 117 and Cortana are declared MIA. It is unknown if they were ever found.