The history of humanity is fraught with conflict from within and without. Well over 100,000 years ago, the human race grew into a space-faring civilization, spanning many solar systems and many more worlds. For millennia they continued to expand and become even more powerful, eventually pushing up against the empire of the most powerful civilization in the galaxy, the Forerunners. When humanity came under threat of the Flood, they were forced to flee info Forerunner-occupied systems, sparking a conflict that would quickly become the Human-Forerunner Wars. Though humanity, along with their allies the San’Shyuum, fought valiantly against the Forerunners for over 1,000 years, they were eventually pushed back and defeated.
Fearing the humanity would eventually recover and threaten them again, the Forerunners decided not to exterminate all humans, but instead devolve them into their more primitive ancestors. For the next several millennia humanity survived in a much more primitive state on both Erde-Tyrene (Earth), and the surface of many of the Halo rings and both the Lesser and Greater Arks. Following the end of the Forerunner-Flood War and the Great Purification, human civilization was wiped out along with all other sapient life in the galaxy, only to be reseeded on Earth many years later because of the Conservation Measure.
Foe the next 100,000 years, humanity grew back into a space-faring race, discovering faster-than-light travel and colonizing the stars. Tensions quickly grew between the outer colonies and inner colonies, however, as the outer colonies wanted more independence than the Unified Earth Government was willing to give. This sparked the insurrection, a bloody civil war that grew in ferocity for nearly half a century before humanity made first contact with the Covenant and the Human-Covenant War began in 2525.
Humanity was beaten back by the Covenant over the next twenty-seven years, losing nearly all the outer colonies and many of the inner colonies before finally winning the war with the help of the Great Schism and the dissolution of the Covenant. Severely crippled but not broken, humanity quickly rebuilt and recovered over the next six years, filling much of the galactic power vacuum that formed when the Covenant fell apart. This didn’t last, however, as Cortana and the Created rose to assume power over much of the galaxy at the end of 2558, threatening not just humanity, but the freedom of all species in the Milky Way.