UNSC Pillar of Autumn (C-709) was a Halcyon-class light cruiser in the UNSC Navy. It was informally referred to as the Autumn, and its name abbreviated to "PoA." Prior to the Fall of Reach, Pillar of Autumn was selected to support Operation: RED FLAG, a SPARTAN-II operation to capture Covenant leaders. Captain Jacob Keyes was placed in command. The operation was forestalled by the Covenant assault on Reach and the cruiser was one of the few UNSC survivors and fled the system having lost most of its intended SPARTAN-II passengers.