From Halopedia, the Halo wiki
The Anvil Initiative is a cross-training and evaluation program of the UNSC Armed Forces' Spartan Operations, operated in collaboration with the Swords of Sanghelios. The Anvil Initiative provides Spartan-IVs an opportunity to directly interact and train with Sangheili warriors in both shared War Games and live exercises. Anvil also tests hybrid technologies developed by the Office of Naval Intelligence, corporate partners, Sangheili artisan-armorers, and special research collaborations.
Behind the scenes
Anvil Station served as the setting for the War Games simulations featured in the cancelled game Halo Online. The station was likely associated with the Anvil Initiative, given its name and the inclusion of Sangheili within Halo Online.
List of appearances