The operation was to be executed in four phases. The first phase consisted of the disabling and capture of a Class-Five Covenant vessel. As such vessels only appeared in combat zones to collect Forerunner artifacts, this phase would require the use of a colony located on a planet with a high concentration of such items as bait. It would also require the retrofit of a cruiser, either Halcyon or Marathon-class, to be capable of conducting in-atmosphere operations and surviving the punishing firepower of a Covenant capital ship. For the first phase, Dr. Halsey selected Captain Jacob Keyes to command the newly fitted cruiser UNSC Pillar of Autumn for his exemplary performance during the Battle of Sigma Octanus IV.