Calamus sailed from Norfolk, Virginia, 13 September 1944, bound for Pearl Harbor and Ulithi, where she arrived in mid-December and began her work as station tanker, fueling ships of the fleet as they brought the war ever closer to the Japanese homeland.

Calamus cleared for Eniwetok 20 January 1945, and until February, pumped her vital gasoline into the ships readying there for the assault on Iwo Jima.

Following the fleet she served westward, Calamus did station duty at Saipan from 11 February until 26 April, when she anchored off Okinawa to support the 3-week-old assault.

The tanker provided essential fueling service through the entire period of the island's assault and occupation, enduring the violent Japanese air attacks which marked the campaign as steadfastly as did the combatant ships.

Following occupation service, Calamus returned to San Francisco, California, 20 March 1946 and was struck from the Navy list (date unknown).