The San 'Shyuum Civil War has come to a close and the victorious Reformists march onward aboard their newfound Holy City. First contact with the Sangheili results in the Sangheili-San 'Shyuum War. Finally, we reach the point where this mysterious universe splits-off from our own. An unaccountable space-time anomaly leads to a vital Sangheili victory. The war ends in a stale mate and amends are made. The Sangheili are willing to overlook the Covenant's usage of High Charity as long as they agree not to affect, utilize, or bring harm to any other Forerunner relics in the future. The Sangheili are even willing to join the San 'Shyuum in order to enforce this compromise. The San 'Shyuum are to be recognized as Prophets, the alliances primary political leaders. The Sangheili serve primarily as military leaders. The San 'Shyuum reluctantly agree to these conditions, refusing to give into any more of the Sangheili's requests. The alliance is formed, and the union becomes known as "The Progeny". Continuing long into the future, The Progeny continues to grow by graciously and charitably acquiring willing species into it's union. The Progeny's foremost goal is to guard and protect the Halo Array.
How could this come about? How could humans come to be engaged in an aggressive war against the self-proclaimed protectors of the legacy of the Forerunners? In order to find out, one must go to before the war. To a time that had also existed in the universe that we have become so familiar with... back to the mid-22nd century. A time when remnants of old cultural ideologies clashed for supremacy in the Solar System. The slight, inexplicable interference caused by a rare time-space anomaly having occurred a great many thousands of years ago affects one minor battle. The tides changed. A rapid succession of military failures began to plague the United Nations Space Command. The UNSC ultimately collapses, bringing the Unified Earth Government down with it. The insurrection takes Earth.
First contact between the Covenant and humanity began when a Covenant missionary ship, the Minor Transgression, had entered the Epsilon Indi System. The starship quickly scanned a nearby colonized known as Harvest before unexpectedly being intercepted and destroyed by multiple overly-aggressive INSC cruisers.
Following quickly on Minor Transgression's heels was the Covenant cruiser, Rapid Conversion. The cruiser's commander, the Jiralhanae War Chieftain and Ship Master Maccabeus, was ordered to establish peaceful negotiations with the humans.
On February 3rd, 2525, Tiara, Harvest's orbital station, detected Rapid Conversion entering the system on long range sensors; the cruiser registered as an unknown object but determined the ship was constructed of materials beyond human science. Diplomatic meetings were quickly scheduled between high-ranking Progeny officials and Attorney General Alexander Bandlen, accompanied by the Harvest Colonial Militia. Bandlen saw his chance to acheive glory for the Empire in an ambush, that would prevent the Progeny from possibly inciting further support for the Demcratic Resistance, and had the militia kidnap Maccabeus and hold him for ransom in exchange for technology. Maccabeus was ultimately murdered after having wounded a member of the militia named Walter Danmeyer during an rescue attempt by the Progeny. A vengeful Tartarus lead an assault on the planet, officially declaring war.