From Halopedia, the Halo wiki
Cote d'Azure was a UEG colony world. 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". This suggests the presence of Forerunner structures on the planet, as well as indicating why it was one of the first planets the Covenant attacked.
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