In 1943, with Papua New Guinea secured and the Buna-Gona campaign successfully resolved, "Trinity" moved her base to Milne Bay, New Guinea, where she arrived on 13 August 1943 and came under the control of Commander, Base Force, 7th Fleet. Attached to this command for the remainder of the year, "Trinity" the Milne Bay-Brisbane route, while also touching at Cairns and Townsville, Australia. When anchored at Milne Bay, she provided oil for miscellaneous Allied ships. She subsequently moved north to commence operations in the Buna-Cape Cretin vicinity, an area in which she remained until early March.