SUMMARY
Operation: FIRESIDE was an ODST mission to investigate a distress call sent by civilians on the colony world of Ariel, which had come under attack by Covenant forces days earlier in late December 2551 or early January 2552. During the mission it is discovered the Covenant are attempting to recover a Forerunner AI, known as the Knowing. In the course of battle, the ODSTs discover the Knowing and convince it to self destruct, rather than fall into Covenant hands. The loss of the Knowing spurs the Covenant to retreat, saving the colony from destruction.
RELATED MEDIA
These events are referenced in the comic Halo: Helljumper, and was the subject of a Halo Book Club episode on November 29th, 2014.