The game will tell you that Halo Wars’ story began on February 4, 2531, but the truth is that it began almost six years prior to that day on the colonial world of Harvest, where humanity first came face to face with the Covenant. On February 23, 2525, shortly after an initial encounter which went horribly awry, the Jiralhanae forces aboard the Rapid Conversion attempted to seize Harvest for the glory of the Covenant. The first series of ground attacks were staved off by a local militia and a large number of the colony’s population escaped unscathed — but the battle, however, was far from over.
Buried in the outlying Epsilon Indi system, the farm planet was too remote for any effective UNSC response, so after contact was lost, they sent the Argo. When the ship arrived on April 20, 2525, it ran headlong into a Covenant fleet in the middle of glassing Harvest’s surface. The ship was able to send one confirmation message to the UNSC before falling off the grid itself, clearly having been attacked by the alien aggressors.
A full six months later, on October 7, 2525, UNSC Battlegroup 4 arrived at Harvest. The three vessels in its fleet are almost immediately destroyed by a single Covenant warship, and only one of the three escaped back to the UNSC fortress planet of Reach. Upon its return, the military mobilized one of the largest fleets in UNSC history under the command of the once-retired Vice Admiral Preston Cole. His forces arrived in orbit above Harvest on March 2, 2526, and were narrowly successful in eliminating the Covenant ship. Despite Cole’s fleet losing 13 of its own vessels during this battle, they finally reclaim Harvest.
Around the same time and at the other end of the galaxy, a powerful Sangheili warlord by the name of Ripa ‘Moramee attempted to overthrow the leadership of his own clan on the base world of Decided Heart. Despite earlier successes against humanity and various heretical branches of the Unggoy and the Kig-Yar races, ‘Moramee was unable to oust his clan’s military leader, and his efforts resulted in a sentence of imprisonment.
Almost immediately escaping this capture, he quickly found himself in the clutches of a hierarch — one with an offer of absolution for his failed coup d’état. Having gained some favor with the High Prophet of Regret due to his fanatical military record and appetite for brutality, ‘Moramee was pardoned for his crimes and freed to return to military service against humanity. The one requirement was that he carried the holy and suicidal mantle of the Seventeenth Arbiter in the line of Immaculate Succession — essentially, that he would lead the entire Covenant campaign against humanity and that he would do so without question.
In the subsequent years after Cole’s initial victory, other colonial worlds are lost to the Covenant as they plague the outer rim of UNSC-controlled space. Strangely, however, the aliens continued to return to Harvest in the years following their first attack. During one of these subsequent encounters, a UNSC vessel called the Prophecy was attacked as it attempted to determine the source of the Covenant’s curiosity.
On January 3, 2531, the support ship Spirit of Fire was sent by Admiral Cole to determine what happened to the Prophecy. Historically speaking, the Spirit was fairly unique in UNSC military deployment, as it had once been used to ferry humans from overpopulated worlds to their new colonial homes. Now used to bring military personnel and equipment to warzones, the Spirit had been refitted to be a powerful supply ship under the guidance of a smart AI construct by the name of Serina. The irony of the Spirit’s mission to investigate the Prophecy did not escape its captain, a man by the name of James Gregory Cutter. He had been previously offered a command position on the Prophecy three years prior — now, instead of serving on it, he would be attempting to rescue it.
On February 4, 2531, the Spirit of Fire entered orbit and found the Prophecy inert and its crew contaminated by radioactive exposure. Despite all efforts otherwise, there were no survivors. The Cole Protocol is enacted on the Prophecy and its data banks were wiped clean.
Meanwhile, a professor by the name of Ellen Anders was offering a lecture discussing some of the ancient and mysterious relics which have been discovered through out UNSC-controlled space, including Côte d’Azur and Onyx. Afterward, she is apprehended by agents of the Office of Naval Intelligence and eventually. Forced aboard a transport The Last Gleaming, she is tasked by ONI with the study of intercepted Covenant transmissions; ones which they had found great difficulty in deciphering.
On her way to rendezvous with the Spirit, Anders breaks the code in the Covenant communiqué and discovers that they have dispatched an “Arbiter” to Harvest to quell “political unrest.” Beyond this, however, no more information could be obtained from the transmissions.
Transported to the Spirit of Fire, Anders, with the backing of FLEETCOM, advises the crew to immediately pick up where the Prophecy had left off: investigating the Covenant’s actions on Harvest. Cutter dispatched Sergeant John Forge, a battle-hardened but somewhat reckless Marine, directly into Covenant lines. After supplying some reconnaissance on the Covenant’s interest in what was found to be a previously unknown structure buried in the polar region, he is tasked with redeploying the UNSC forces, pushing the Covenant into the ancient structure’s interior and quickly defeating them — the Arbiter, however, was nowhere to be found.
Inside, Anders determined that the structure belonged to ancient race which had once occupied Harvest — known to us as the Forerunners. Using a device at its core, she learned that the relic housed what was essentially a map room, and upon her touching a spherical console, a holographic milieu of star systems appeared with designation lines connecting them at various junctures. Within moments, Anders and her accompanying Marines are attacked by a hidden vestige of Covenant forces still within the relic. Forge demands immediate evacuation and the Marine detachment is plucked from the surface of Harvest and returned to the Spirit of Fire.