From Halopedia, the Halo wiki
Around the time Master Chief John-117 arrived on the fragmented section of Zeta Halo, Banished forces attacked Courier Squad. At some point after the Chief stormed the Tower and killed Chak 'Lok, the Spartan's AI companion, The Weapon, picked up Courier's distress call, prompting the Chief to rescue the marines.
In Halo Infinite, Courier Squad is found in the "Connections" section of the campaign. Answering their distress call earns the player 30 Valor points. This valor is awarded even if all members of Courier Squad are killed.
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