Fleet of Furious Redemption
From Halopedia, the Halo wiki
During the invasion of the Sol system in late October and November of 2552, the fleet was sent to Mars and apparently raided the planet. They captured at least one human prisoner, Colonel James Ackerson, with the intent of executing him in a victory ceremony once they made it to the ongoing battle on Earth. In an effort to stall their advance and save his own life, Ackerson divulged the existence of the fictional Key of Osanalan, prompting the Covenant to invade the city of Cleveland in search of it. It is unknown whether any elements of this fleet participated in the battle.
Following the battle, the fleet remained in Martian orbit. Ackerson revealed to Lepidus, shipmaster of the Ket-pattern battlecruiser Triumphant Declaration, that the Key was a hoax, prompting the Brute captain to behead him.
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