For more than two years
Millicoma provided valuable at-sea logistics support as the might of American seapower moved westward across the
Pacific Ocean to crush the warring
Japanese Empire. Refueling and replenishment operations sent her throughout the Pacific to the islands of
Polynesia,
Melanesia, and
Micronesia as well as to the home islands of
Japan. During her
Pacific Ocean service she refueled scores of ships ranging in size from
battleships and
aircraft carriers to
destroyers and auxiliaries. She transferred thousands of barrels of oil and thousands of gallons of gasoline to the fighting ships of the fleet and thus helped the Navy press the war to a successful conclusion. Departing
Norfolk, Virginia, on 20 April 1943,
Millicoma steamed via the
Dutch West Indies and the
Panama Canal to carry a cargo of fuel oil and gasoline to the
Fiji Islands. During the remainder of 1943 she continued to carry vital liquid cargoes to American bases in the
South Pacific. Operating out of
San Pedro, California, she made several runs to the
Society Islands, the
New Hebrides,
New Caledonia, and
New Zealand. Thence, after completing a round trip to
Hawaii and back, she departed San Pedro on 13 January 1944 to begin supporting the Navy's series of island‑hopping campaigns.
Millicoma refueled ships off the
Marshall Islands prior to and during the invasion; thence, arriving
Majuro on 4 February, she served as station oiler in the Marshalls until sailing for the
New Hebrides on 2 March. Between 31 March and 15 April she cruised north of the
Solomon Islands and refueled ships of
Task Force 58 following intensive air strikes in the western
Caroline Islands. After returning to San Pedro on 9 May, she underwent overhaul and on 20 June sailed to resume fleet oiler duty in the Marshall Islands. Early in July she cruised for similar duty in the Marianas, and during the next month she supported fleet operations off
Tinian,
Guam, and
Rota. She returned to
Eniwetok on 12 August, and between 26 and 31 August steamed to the
Admiralties for duty with the At Sea Logistics Support Group (
Task Group 30.8). Early in September she refueled ships of the fast carrier task force during sweeping, hard-hitting strikes from the
Palaus to the southern
Philippines. At 0434 on 10 September, while maneuvering in a hazy half-light, she was involved in a collision with . Schuylkill's bow struck her sister ship on her starboard quarter, which opened a 40-foot hole, including her steering engine room. Her 5" and 3" gun mounts were also demolished. She made repairs at
Seeadler Harbor alongside the newly arrived and sailed for
Terminal Island, California 9 days later.
Millicoma returned to the
U.S. West Coast on 19 October. Departing San Pedro, California, on 1 December, she steamed via
Pearl Harbor and
Eniwetok to
Ulithi where she resumed duty with Task Group 30.8. She sortied 3 January 1945 and during the next three weeks cruised the replenishment areas in the western Pacific and refueled the fast carriers during far-reaching operations against Japanese installations on
Luzon,
Formosa,
China,
Indochina, and the
Ryukyus.
Millicoma served out of Ulithi during the remainder of
World War II as she continued a busy pace of fleet replenishment operations which carried her to the heart of the
Japanese Empire. In late February and early March she replenished ships during the conquest of
Iwo Jima. Besides fuel, she provided ships with foodstuffs, medical supplies, ammunition, and mail. Thence, beginning on 13 March, she sailed on the first of four major fueling operations in support of the invasion and conquest of
Okinawa. She carried out additional deployments on 30 March, 22 April, and 30 May, and each of the four runs lasted about two weeks. While cruising with Task Group 30.8 on the fourth deployment, she battled
typhoon seas on 4–5 June. Sixty-foot waves and winds in excess of destroyed her fueling booms and cracked her
foremast. She returned to
Ulithi on 11 June for repairs, thence departed for
Okinawa on 28 June to begin shuttling fuel to the newest of the American bases in the western
Pacific. She completed two round trips to the
Ryukyus and returned to Ulithi where she received news of Japanese capitulation.
Millicoma steamed to Japanese waters on 8 September and refueled minesweep and support ships off
Sasebo,
Kyūshū. She replenished more than 60 ships in less than two days. She arrived Sasebo on the 29th to continue logistics support of minesweeping operations, and between 22 and 25 October she refueled ships in the
Yellow Sea along the coast of
Korea. == Post-War operations==