The Raid on Ivanoff Research Station was a conflict between UNSC forces and a coalition of Jul 'Mdama's Covenant and the forces of the Ur-Didact over the possession of a Forerunner artifact known as the Composer.
Traveling from Requiem to Installation 03, the Ur-Didact and Jul 'Mdama's Covenant assaulted Ivanoff Research Station in an attempt to locate the Composer. The Ur-Didact knew it was inside the station, but did not know where specifically. The Ur-Didact's ship scanned the station while Phantoms, Liches, and Rangers began boarding it to manually search for the Composer's location.
The station's scientists and security forces were quickly being overwhelmed until the appearance of John-117, who had stowed away on a Lich after the First Battle of Requiem and used it to board the station. John contacted the head scientist of Ivanoff Station, Sandra Tillson. John and surviving security forces managed to raise the landing bay shields, preventing more Phantoms from entering.
John met with Dr. Tillson in person and concluded that a HAVOK nuclear device needed to be detonated to prevent the Ur-Didact from obtaining the Composer. John reactivated the station's outer defense turrets, which destroyed several Phantoms and helped cover evacuation shuttles. However, Covenant forces inside the station managed to drive off all of the humans guarding the Composer. John climbed into a Mantis and engaged them, destroying several infantry squads and holding off waves of Banshees and Phantoms that were deploying Ghosts and Wraiths. Suffering heavy casualties, the Phantoms retreated back to the cruisers, but the Ur-Didact's ship was able to pull the Composer out of the station.
John and Cortana realized the Ur-Didact was preparing to fire the Composer on Ivanoff Station and attempted a preemptive attack using the station's defenses, but they were too late. The Ur-Didact fired the Composer, killing all the remaining humans except John. The Ur-Didact then prepared to travel to Earth while the surviving Covenant returned to Requiem.
Many of the scientists who were evacuated in the early stages of the raid, landed on nearby asteroids. They were later picked up by search and rescue teams.