Carrier Strike Group Fifteen, abbreviated CSG-15 or CARSTRKGRU 15, the U.S. Fleet Forces Command formation charged with training and certifying Pacific Fleet Carrier Strike Groups, Amphibious Ready Groups, and independently deploying surface ships, replacing Strike Force Training Pacific. Previously, CSG-15 was one of fourteen U.S. Navy carrier strike groups established on 1 October 2004. U.S. Navy carrier strike groups are employed in a variety of roles, all of which involve gaining and maintaining sea control. Before 1 October 2004, the group was known as Cruiser-Destroyer Group 1. The group commander served as Immediate Superior-in-Command (ISIC) for the ships and units assigned to Carrier Strike Group Fifteen. As an Operational Commander, the group commander exercised oversight of training, integrated training, and readiness, as well as maintaining administrative functions and material readiness tracking for ships and squadrons assigned to the group. Carrier Strike Group Fifteen was initially based at Naval Station Norfolk, Virginia, prior to changing its homeport to Naval Air Station North Island, California, with the Nimitz-class nuclear-powered aircraft carrier USSÊRonald ReaganÊ(CVN-76) assigned as its flagship.