From Halopedia, the Halo wiki
Thunder Squad is a squad of UNSC Marines who fought in the Installation 07 conflict. Around the time John-117 arrived on the fragmented section of Zeta Halo, Thunder Squad's marines were holed up inside a cave when they were attacked by Banished troops. The Chief's AI companion, The Weapon, picked up Thunder's distress call, prompting the Spartan to aid the marines.
In Halo Infinite, Thunder 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 Thunder Squad are killed.
List of appearances