During the Battle of Shield 0459, Alpha Platoon encountered unknown aliens while patrolling the base established by the UNSC Spirit of Fire, managing to destroy the coordinating forms. When the Spirit of Fire was attacked by Forerunner Sentinels, Serina attempted to evacuate the platoon directly, but the D77-TC Pelicans were forced to turn back by hostile aerial forms. Along with Bravo Platoon and Charlie Platoon, Alpha Platoon fought its way on the ground through the aliens to get back to base, where they were finally evacuated. However, one Grizzly tank volunteered to remain and help evacuate the other two platoons. The base was abandoned to the aliens, now empty of personnel.