The Halo universe can be broken up into several distinct eras
AboutThe history of the Halo universe spans hundreds of millennia, from the time of the Forerunners one-hundred thousand years ago, through the formation and growth of the Covenant, to humanity’s struggle amidst the stars. These are the key time periods in the Halo universe, and their importance to the greater lore.
Forerunner EraThe Forerunners dominated the Milky Way for the better part of fifteen-million years.
Colonial EraThe invention of faster-than-light travel allowed humanity, crowded on Earth and the colonies of the Sol system, to spread throughout the stars.
InsurrectionThe spread of humanity throughout the galaxy invited differing beliefs and allegiances to grow, culminating in an insurgency that claimed over one-million lives.
Human-Covenant WarHumanity hoped that first contact would be a peaceful and mutually beneficial interaction. It was not.
Post-WarThe fall of the Covenant led to a galactic power vacuum that was quickly filled with opportunistic factions and leaders.
Rule of the CreatedCortana's contact with the Domain birthed the Created, a group of Artificial Intelligences set on removing conflict and suffering through force.