The Human-Covenant War was a major conflict in the fictional universe of the Halo video game series. It took place between humanity and the Covenant, a theocratic alliance of alien species. The war began in the 26th century when the Covenant discovered humanity and viewed them as a threat to their religious beliefs and expansion. The conflict lasted for nearly three decades, resulting in significant loss of life and destruction. Key battles occurred on various planets, with notable events including the fall of Reach and the defense of Earth. The war ultimately ended with the defeat of the Covenant and the emergence of new threats, such as the Flood and the Created.