History of the Covenant

The Covenant, like almost all cultures, kept a record of their history using their own methods of timekeeping. Significant time periods in Covenant history were divided and categorized based on a system of ages, which were assigned into seven categories based on notable events within each. Shorter spans of time were measured based on the Covenant Battle Calendar. Certain time periods within the ages were also given names, an example of which is the Step of Silence.

Each age was broken up into cycles and units, the former consisting of 265 of the latter and corresponding to a single artificial day within the Covenant's holy city High Charity. The last of the ages was the 9th Age of Reclamation, which saw the fracturing of the Covenant during the Great Schism.

The Ages
Rather than following one another in a succession, the ages represent designated periods of time which were defined by a major event during each age and named based on seven main categories. For example, the 23rd Age of Doubt was followed directly by the 9th Age of Reclamation because of the events that occurred during those ages.

Age of Abandonment
The Covenant traces its history back at least 100,000 years, when an ancient species called the Forerunners activated the Halo installations, disappearing from the galaxy. This is referred to as the Age of Abandonment by the Covenant.

Ages of Conflict
The Ages of Conflict were periods of time when the Covenant was embroiled in major conflicts. The first such age occurred directly preceding the formation of the Covenant, when the Sangheili and San'Shyuum waged war against each other in a power struggle. Additionally, the Unggoy Rebellion took place during the 39th Age of Conflict.

Ages of Discovery & Reconciliation
What is known is that the San'Shyuum's discovery of ancient Forerunner artifacts during an Age of Discovery and the end of the war between the Sangheili and the San'Shyuum during an early Age of Reconciliation, became the foundation on which the Covenant was founded upon. The San'Shyuum promised to find the means of the Forerunners' transcendence and the Sangheili promised to protect the hierarchy. These ages marked the beginnings of the Covenant, the start of the Covenant's search for Forerunner artifacts and presumably the Covenant Writ of Union.

Ages of Conversion
The Ages of Conversion were defined by the Covenant subjugating other species in their search for Forerunner artifacts, incorporating them into their society, adding their strengths to their own. It is likely that the Taming of the Lekgolo occurred during one such age, requiring the creation of another Arbiter and defeated them only by threatening to destroy the homeworld of the Lekgolo. Separate Ages of Conversion also likely included the incorporation of the Unggoy, Kig-Yar, Yanme’e and Huragok.

Ages of Doubt
The Ages of Doubt are periods during which the Covenant suffered from varying degrees of internal dissent and began to lose faith in their mission. The last Age of Doubt, the 23rd, was preceded by the 39th Age of Conflict, during which the Unggoy Rebellion occurred. The 23rd Age of Doubt ended in the year 2525, in human counting, leading into the 9th Age of Reclamation.

Ages of Reclamation
The Ages of Reclamation were marked by the discovery of major Forerunner artifacts. The 9th, and final, Age of Reclamation began simultaneously with the onset of the Human-Covenant War in 2525 and lasted until the Covenant's defeat at the Ark in late 2552. Originally, the war had been started by the Prophets of Truth, Mercy and Regret to prevent the majority of the Covenant learning that the humans were "descendants" of the Forerunners, their gods, and that the Covenant religion was based on a lie.

As the decades wore on, tensions rose within the Covenant for a variety of reasons. Some Sangheili grew increasingly frustrated at apparent San'Shyuum favoritism toward the Jiralhanae. Others began to question the validity of their holy crusade, beginning to see the humans as worthy adversaries rather than heretics. After the Changing of the Guard, where the Sangheili Honor Guards were replaced with Jiralhanae, these tensions erupted into full civil war in 2552 with the beginning of the Great Schism, where the Sangheili broke away from the Covenant, wresting away significant territories, personnel and equipment, allying themselves (at least grudgingly) with the humans they had formerly fought.

The Age of Reclamation also marked the discovery of a number of important Forerunner installations and outposts, ranging from minor artifacts uncovered on human colonies, to the massive installations of the Halo Array, such as the individual Halos, to two Shield Worlds, ending with the discovery and subsequent destruction of the Ark where the Covenant met its end at the hands of a combined Sangheili-human force spearheaded by the legendary Master Chief, known amongst the Covenant as "the Demon" and the former Covenant Arbiter Thel 'Vadam.

Known timeline

 * 2200 BCE - The San'Shyuum Schism begins
 * 2100 BCE - The San'Shyuum civil war ends, Reformists flee Janjur Qom.
 * 938 BCE - The San'Shyuum encounter the Sangheili and war ensues between both races. The start of the Sangheili-San'Shyuum war ushers in the first Age of Conflict.
 * 876 BCE - The Sangheili reluctantly begin using Forerunner technology to improve their warships, arms and armor.
 * 860 BCE - San'Shyuum and Sangheili forces battle on the Planet of Blue and Red.
 * 852 BCE - The Sangheili-San'Shyuum war comes to an end, and the Covenant is formed with the creation of the Writ of Union. The first Age of Reconciliation begins.
 * 851 BCE - Sangheili opposed to the Writ of Union rebel against the Covenant.
 * 784 BCE - Taming of the Lekgolo: the Lekgolo are discovered and incorporated into the Covenant.
 * 648 BCE - Janjur Qom is destroyed by a natural stellar collapse and High Charity becomes the surrogate homeworld of the San'Shyuum. The Forerunner Dreadnought is made into the centerpiece of the capital.
 * 1112 - The Yanme'e are incorporated into the Covenant.
 * 1342 - The Kig-Yar are discovered and form an alliance with the Covenant.
 * 1552 - San'Shyuum begin searching for lifespan augmentation methods.
 * 2142 - The Covenant incorporate the Unggoy into their society.
 * 2462 - The Unggoy Rebellion occurs and ends, inaugurating the 29th Age of Doubt.
 * 2492 - The Jiralhanae are discovered and incorporated into the Covenant.
 * 2524 - First public appearance to humanity.
 * 2525 - The Covenant glass Harvest, declaring a genocidal campaign against the so-called "heretics". The 9th Age of Reclamation begins.
 * 2552 November - The Great Schism causes the Covenant to errupt into civil war as the entire Sangheili species are forced out.
 * 2552 December - The Covenant meets its end at the Battle of the Citadel.