"Unless the political situation throughout the colonies is stabilized (preferably by force), the Government will collapse and civil war will rip human society apart."
The Spartan II program, led by Dr. Catherine Halsey, was a plan by the Office of Naval Intelligence to use children with superior genetic traits to create a group of super-soldiers in order to put an end to the ongoing Insurrection in the outer colonies.
On their first mission as fully augmented Spartan-IIs, Blue Team, consisting of John-117, Samuel-034, Linda-058, Kelly-087, and Fred-104, infiltrate Eridanus Secundus, a hidden United Rebel Front base located in an asteroid field, and capture Colonel Robert Watts.
The Second Battle of Harvest, also known as just simply the Battle of Harvest, was humanities first attempt to recover the planet Harvest from the Covenant, who wiped out the existing colony and killed tens of thousands of civilians a year earlier.
The Battle of Hat Yai was a battle early in the Human-Covenant War that took place between late 2528 and early 2529. While the UNSC ground forces were successful in defending against the Covenant attack, the naval battle ended in defeat and ultimately glassing of the planet.
Spartan-III Alpha company was the first of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2531, after being recruited as children orphaned by the war.
In an effort to limit the ability for the Covenant to discover human colonies, including the inner colonies and Earth, the Cole Protocol was established to wipe all ship navigation data when the UNSC came into contact with any Covenant forces.
Spartan-III Beta company was the second of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2539, after being recruited as children orphaned by the war.
Operation: RED FLAG was a planned operation by both the Office of Naval Intelligence and the UNSC to use Spartans to capture a Covenant ship, use it to penetrate into Covenant space, and capture a Hierarch, with the intent of using the Prophet to broker a cease-fire.
Operation: FIRST STRIKE was a mission undertaken by John-117 and several other Spartan-IIs to infiltrate and destroy the Covenant space station Unyielding Hierophant and associated armada of over 500 warships in the Tau Ceti system prior to the Covenant's invasion of Earth.
The Battle of Installation 05 was an engagement between the Covenant forces, including those that fled the Battle for Earth, High Charity, and the Second Fleet of Homogeneous Clarity, and the UNSC-allied forces, including the UNSC In Amber Clad led by Miranda Keyes, and the Fleet of Retribution led by the Arbiter Thel 'Vadam.
The Battle of Installation 00 was a major conflict between the forces stationed aboard the UNSC Forward Unto Dawn and Arbiter Thel 'Vadam's Fleet of Retribution, and the Covenant fleet loyal to the Prophet of Truth. The fighting was the last battle of the Human-Covenant War and culminated in a UNSC victory.
The Spartan-IV program was the third successful Spartan training program and the first since the end of the Human-Covenant War. The first Spartan-IV Class began augmentations and training in 2553, and consisted of 145 candidates.
The Blooding Years is the Sangheili term for the civil war that raged for five years on Sanghelios and throughout Sangheili-occupied territories following the end of the Human-Covenant War and disappearance of the San’Shyuum.
Operation: JOVIAN WHISTLE was an operation executed by the UNSC 717th Xeno-Materials Exploitation Battalion to recover a Forerunner ancilla on the human colony world of Gao in the Cordoba system in the early summer 2553.
The Battle of the Prototype Halo Installation was a conflict between Tem'Bhetek, the former Covenant Minister of Preparation Boru'a'Neem, and the Shadow of Intent crew including Rtas 'Vadum and Tul 'Juran.
Operation: RETRIBUTION was an Office of Naval Intelligence mission headed by operative Veta Lopis and her Ferret team to investigate the murder of Vice Admiral Graselyn Tuwa and the kidnapping of her family members on December 6th, 2553.
The Spartan-IV program was the third successful Spartan training program and the first since the end of the Human-Covenant War. The second Spartan-IV Class began augmentations and training in 2554, and was much larger than the first class size of 145.
The Return to Installation 00 was an Office of Naval Intelligence mission undertaken by the UNSC Rubicon to return to the Ark following the Battle of Installation 00 and investigate the status of the facility in August 2554.
Sometime in January 2557, Rion Forge, a post-war salvager, and her ship the Ace of Spades, discover the location of what was left of the Etran Harborage after the destruction of the shield world during the events of the Battle of the Etran Harborage in 2531.
Following discovery of the last known location of the UNSC Spirit of Fire from the Battle of the Etran Harborage, the Office of Naval Intelligence sent the UNSC Taurokado to investigate the system for any information regarding the whereabouts of the lost UNSC warship.
The Battle of Requiem was a conflict between former Covenant forces under the command of Jul 'Mdama, UNSC forces from the UNSC Infinity and Forward unto Dawn, and Promethean forces under command of the Ur-Didact on Forerunner Shield World 0001, also known as Requiem, in July 2557.
The Battle of New Phoenix was a military engagement between the UNSC and Covenant remnant forces under command of Jul 'Mdama in the city of New Phoenix on Earth, immediately after the New Phoenix Incident and the Battle of Installation 03 in July 2557.
The Assassination of Avu Med 'Telcam was an assassination sanctioned by the Office of Naval Intelligence Section Three and carried out by SPARTAN-G059 on the leader of the Servants of the Abiding Truth on former colony world New Llanelli in the Brunel system in January 2558.
The Battle of Kamchatka was a battle between Covenant remnant forces under the leadership of Jul 'Mdama, local Promethean forces under control of Cortana, and the UNSC in the form of Spartan-IV Fireteam Osiris on the planet of Kamchatka in October 2558.
The Battle of Nuusra was a battle between the remnants of Jul 'Mdama's Covenant forces, the Swords of Sanghelios, and Spartan-IV Fireteam Osiris in the sate of Nuusra on the continent Qivro on the Sangheili homeworld of Sanghelios on October 27th, 2558.
The Battle of Sunaion was a battle between the Swords of Sanghelios led by Thel 'Vadam, their allies Fireteam Osiris led by Jameson Locke, the last of Jul 'Mdama's Covenant forces, and the Created forces led by the Warden Eternal in the state of Sunaion on the Sangheili homeworld of Sanghelios.