From Halopedia, the Halo wiki
The Bhaakto system is a planetary system of at least three planets, with the third being Alluvion. In 2412, Alluvion was colonized by humanity, located on the border of the Inner Colonies and the emerging Outer Colonies. In 2542, Alluvion was invaded by the Covenant and glassed. However, following the Human-Covenant War, the planet was eventually resettled by the Unified Earth Government in 2554.