Shortly after a ten-day shakedown period, "Manatee" departed the Chesapeake Bay area for the Dutch West Indies. Loading at that oil center, she got underway for the Panama Canal and the Pacific. Arriving at Eniwetok 16 June 1944, she replenished the amphibious forces then invading Saipan. She shuttled from Eniwetok to the fueling areas throughout the campaigns for Saipan, Tinian, and Guam, until moving to Manus, largest of the Admiralty Islands, 20 August. From Manus, she continued carrying fuel and other supplies to fast carrier groups through the Battle of Peleliu and the first phase of the Philippine Campaign. By 20 October, when "Manatee" departed Manus for the last time, the atoll Ulithi at the western edge of the Caroline Islands had been secured and established as a regional center for fleet oilers.