USS "John S. McCain" spent her first year of commissioned service undergoing sea trials and shakedown training in the Atlantic Ocean and Caribbean Sea. One of the of large and fast destroyer leaders, she carried the new guided-missile armament, and she embodied new ideas in hull design and construction. This warship arrived at Norfolk on 19 May 1955 to begin service with the Operational Development Force in testing new equipment and tactics. She operated out of Norfolk until 5 November 1956, when she steamed from Hampton Roads bound for the Panama Canal and San Diego, California. After her arrival on 4 December 1956, she spent five months on maneuvers in the Pacific Ocean off California.