held trials of her new equipment off San Clemente Island. A midshipman training cruise occupied a large part of her summer. The destroyer sailed on 19 October for the Western Pacific. Following stops at Pearl Harbor and Subic Bay, Arnold J. Isbell relieved the destroyer on 30 December on the northern search and rescue (SAR) station in the Gulf of Tonkin and began her first duty in the combat zone off the coast of Vietnam. The warship then became a unit of TF 77. Search and rescue duties occupied the vessel until she was relieved on 31 March 1966 and sailed to Hong Kong for four days of rest and relaxation. On 12 April, she got underway to return to the United States. After fuel stops at Midway and Pearl Harbor, Arnold J. Isbell reached Long Beach on 28 April and commenced a leave and upkeep period. She returned to sea on 11 June with a midshipman training cruise to Hawaii and several fleet exercises. The destroyer unloaded her ammunition at Seal Beach, California, on 29 July and entered the Mare Island Naval Shipyard on 31 July for overhaul. Refurbished, the ship began a training period on 16 September and spent the remainder of the year in exercises along the southern California coast and in upkeep during the Christmas holidays. Arnold J. Isbell held refresher training out of San Diego in March 1968 and then conducted local operations until getting underway for the western Pacific on 15 July. She arrived on station off the Vietnamese coast on 12 August and carried out duties as a gunfire support ship. Her routine was broken only by brief periods in port for repairs and liberty for the crew. The destroyer spent the Christmas holidays patrolling off Vietnam and then visited Subic Bay, and Yokosuka. On 20 January, Arnold J. Isbell headed home. Upon her arrival at Long Beach on 31 January, she commenced a three-month period of leave and availability. She got underway again on 21 April for brief cruise to Acapulco and Manzanillo, Mexico, but was back in home port on 5 May. The vessel joined Task Group 10.1 on 9 June for a midshipman training cruise. Ports visited during this assignment included San Francisco, Seattle, Washington, and Pearl Harbor. This cruise terminated on 31 July, and she returned to Long Beach. A tender availability alongside the destroyer tender ensued, and the