Upon completion of sea trials and outfitting, "Guadalcanal" departed Philadelphia to join the Amphibious Forces, U.S. Atlantic Fleet. One of a new class of ships designed from the keel up to embark, transport, and land assault marines by means of helicopters, she lent new strength and flexibility to amphibious operations. After departing Norfolk 23 October 1963 for six weeks' shakedown training at Guantanamo Bay, Cuba, "Guadalcanal" steamed to Onslow Beach, North Carolina, 6 December for practice amphibious landings. She then carried on training and readiness operations with the Atlantic Fleet, based in Norfolk until departing for Panama 11 February 1964. Following 2 months on station as flagship for Commander PhibRon 12 with the 12 Marine Expeditionary Unit embarked and ready to land anywhere needed. "Guadalcanal" entered Philadelphia Naval Shipyard 26 May, but was deployed again 7 October as a unit of Operation "Steel Pike 1", a NATO landing exercise on the beaches of southern Spain.