Following exhaustive shakedown training out of Bermuda, the new destroyer arrived Norfolk on 28 March 1944. Sailing for the Pacific via the Panama Canal, she arrived Pearl Harbor on 23 April 1944. After operational training, "John D. Henley" escorted fleet oilers to Majuro and returned on 17 May. She departed on 27 May for Majuro once more and there became flagship of a refueling task group. Departing on 6 June 1944, the ships moved to the Marianas to refuel the fleet during the capture and occupation of Saipan and Tinian. During this long at-sea period the ships came under air attack 17–18 June. They returned to Eniwetok 14 August.