The Battle of the Etran Harborage was a battle between the UNSC Spirit of Fire and Covenant forces lead by Arbiter Ripa 'Moramee on Shield World 0459, also known as the Etran Harborage. The Spirit of Fire followed the Covenant to the shield world after professor Ellen Anders was captured and taken there to gain access to the Forerunner dreadnoughts stationed there. The battle was humanity's first known encounter with the Flood, and resulted in the destruction of the shield world and all the Forerunner dreadnoughts. While the UNSC Spirit of Fire ultimately escaped, it lost its slipspace drive and was left adrift in space with all hands placed in cryo-sleep.
These events are depicted in the video game Halo Wars.