From Halopedia, the Halo wiki
On July 12, 2519, Vance and the rest of his squad had been assigned to guard an Albatross dropship during a Spartan-II training mission at the Military Wilderness Training Preserve in the Highland Mountains. They were tasked to ambush the Spartans when they arrived at the dropship. Because the armed men were out of their uniforms and bore no insignia, they were perceived by the Spartan trainees as hostiles. Vance was lured by Trainee 087 and came across Trainee 034, who told him that he had a broken leg. As Vance prepared to use his stun baton on the Spartan, he was pelted by stones and knocked out by the other trainees. The Spartan-IIs then attacked the remaining men and commandeered the Albatross back to home base.
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