It was sent in October 2552 to survey the debris field of the destroyed Installation 04. It arrived in-system some time after the Covenant Fleet of Particular Justice and High Charity had departed.
While stationed at the derelict Installation 04 the Red Horse's crew picked up several escape pods and cryo chambers from the Mona Lisa, a prisoner transport. None of the occupants were alive, except for one man who had managed to escape from the prison ship; however, he died soon after being rescued. Foucault was ordered to send a squad of 18 marines to the Mona Lisa to investigate. However, a Covenant ship soon arrived, making any backup impossible. Eventually, it was discovered that the Mona Lisa had been overcome by a strange infection. The Red Horse was forced to destroy the prison ship with Shiva nuclear missiles. While orbiting Threshold, they got conclusive scans of a gas mine dubbed Colossus. These scans were used to create a War Games simulation.
The prowler had a six-year old onboard Artificial intelligence called Rebecca, which, right before the mission, had replaced Chauncey, the ship's more likable, fully functional, three-year old A.I.
- The ship's name is probably a reference to one of the Four Horsemen of the Apocalypse, War, who is said to ride a red horse.
- Halo: Evolutions - Essential Tales of the Halo Universe
- The Mona Lisa (First appearance)