From Halopedia, the Halo wiki
In February 2558, Fireteam Crimson was sent to the location designated "Two Giants" to investigate a Forerunner beam emitter. The valley came under siege by a Zanar-pattern light cruiser, which sent wave after wave of Covenant infantry and vehicles against Crimson. Infinity Sub-Vessel 3 was dispatched from orbit to relieve the Spartans, and promptly destroyed the light cruiser with a single shot from its MAC gun.
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