The Great War

The Great War, a name often applied to the Human-Covenant War, covers historical events during that conflict from 2525 up to its conclusion in 2552. As the war marked the intersection of the two civilizations' timelines, both human and Covenant-related events are listed; for prior events, Human history and Covenant history should be used. The Great War is followed by the Reconciliation Era, beginning in 2553.

To view all of the era pages, see Timeline.

2520s
The 2520s saw the beginning of the war, with the Covenant making massive advancements into human territory at a frantic pace in the first three years. Despite the UNSC's attempts to tie the Covenant down at Harvest, along with the successful counterattack of Operation: SILENT STORM, large swathes of colonies in FLEETCOM Sector 2 had been glassed by the end of the decade.

2525

 * May 14: The Ascension ceremony of the High Prophets of Truth, Mercy and Regret, the formal beginning of the Ninth Age of Reclamation, and the announcement of the holy war against humanity to the Covenant masses.

2530s
In the 2530s, the main front of the war gradually shifted to FLEETCOM Sector 1 as new invasion routes were opened in the Orion-Eridanus region, though with the destruction of the K7-49 shipbuilding plant the front eventually died off, sparing some of the inner Orion-side colonies; without Operation: PROMETHEUS, Reach (and even Earth) may have been discovered over a decade earlier.

2534

 * The enters service.

2537

 * The and  enter service.

2540s
The early to mid 2540s were marked by a decreasing operational tempo. There were fewer attacks, and the Covenant fleets were smaller. There was a hope on the UNSC side that the Covenant had exhausted their supply routes, or were possibly suffering from war fatigue. It was even thought that the battle of Psi Serpentis broke the Covenant's back. The Pleiades Corridor invasion route, which had been established in the late 2530s, began the Covenant's incursion into Sector 4, though battles also continued elsewhere, namely the inner Scorpius front in Sector 2. The refinery at Pegasi Delta was constructed soon after to push deeper into human territory, though its destruction in Operation: TORPEDO saw the end of the concerted push into the Sector 3 Outer Colonies in the Aquila-Sagittarius side and the redirection of the Covenant's attention toward the Inner Colonies. Against the UNSC's hopes, the Covenant's pace picked up in the later half of the decade, continuing up until late 2552.

2543

 * The enters service.

2547

 * The enters service.