2530: THE COVENANT WAR BEGINS
On April 3, 2530, contact with the Outer Colony, Harvest, is lost. After failing to re-establish contact with Harvest, the Colonial Military Administration sends a scout ship, the Argo, to investigate. Contact with Argo is subsequently lost after arriving in the Harvest system.
The CMA dispatches a battle group to Harvest, consisting of three warships. The lead ship in the battle group, the Heracles, returns to Reach, badly damaged and with heavy casualties. The ship's commander reports that an alien warship with powerful weaponry was present, and had decimated Harvest, exterminating the colonists (and presumably destroying the Argo). The battle group engaged the alien warship, and was thoroughly routed. The Heracles-following the destruction of the other two ships in the group-jumped out of the system, but due to the damage she had sustained, took several weeks to make it back to Reach.
The Earth military goes on full alert, and begins making preparations to move in and retake Harvest. By December, a massive Earth war fleet under Vice Admiral Preston Cole mobilizes, one of the fastest such mobilizations of such a large fleet in the history of humankind.
2531: THE BATTLE OF HARVEST
Cole's war fleet engages the alien warship responsible for the decimation of the colony, scoring a victory (though the battle cost Cole two-thirds of his battle group). Only a last minute tactical inspiration turned the tide of battle.
After returning to Earth, Cole-promoted to Admiral-learns that a number of outlying colonies have been destroyed, leaving behind no survivors. Cole begins to move his fleet around, trying to intercept the invaders. Ground and ship-to-ship battles begin in earnest, raging throughout the Outer Colonies. During one ground engagement, Human forces capture one of the aliens. Before succumbing to his wounds, interrogators learn that the aliens refer to themselves as "the Covenant" (roughly translated).
2535: THE OUTER COLONY MASSACRED
In the course of four short years, Cole's forces are hammered, despite his excellent leadership and tactical brilliance. It is simply a matter of being outgunned; Covenant kill ratios tend to top four to one in ship-to-ship combat. By 2535, virtually all of the Outer Colony worlds have been destroyed by the Covenant. The "Cole Protocol" is established by military order: all human vessels must ensure that Covenant forces do not find Earth. Human ships must-when forced to withdraw-not move on to an Earth bound vector, even if that means jumping without proper navigational calculations. If blind jumps are not possible, the ship's captain must order self-destruction if capture is imminent. In addition, it is also imperative that the powerful ship A.I. data cores not fall into Covenant hands, so part of this protocol involves either the removal or destruction of the ship's A.I. in extreme situations.