Combat Team Sierra was stationed aboard the UNSC Pillar of Autumn in 2552. During the abandonment of the warship to the Covenant bombardment and boarding, the team's objective was to hold off the invaders until all non-bridge operations personnel and Combat Teams Alpha through November escaped in the lifeboats, and subsequently, fall back to an evacuation station aboard the Pillar of Autumn. All of Combat Team Sierra was KIA after a malfunction on their Bumblebee lifeboat caused the pod to crash with all passengers dead, other than John-117.