From Halopedia, the Halo wiki
The colony was glassed in the first four years of the Human-Covenant War, being one of the first eight human colonies to fall to the Covenant. During a lecture at Rishard University on Arcadia in February 2531, Professor Ellen Anders claimed that the planet had "large-scale engineered features".
In Halo: Ghosts of Onyx, the city of Cote d'Azur on Sigma Octanus IV is sometimes referred to as "Cote d'Azure". However, given the timeline of the data pads, it would suggest the two are separate.
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