"Southampton" entered Pearl Harbor on 26 November and, for the next two months, participated in amphibious exercises in the islands. She departed Pearl Harbor on 27 January 1945 with members of the 25th Regiment, 4th Marine Division, embarked. The AKA arrived at Eniwetok in the Marshall Islands on 5 February and, two days later, headed on to Saipan. She made Saipan on the 11th, conducted final invasion rehearsals off Tinian between the 13th and 15th, and got underway for Iwo Jima the following day. "Southampton" entered her assigned transport area off Iwo Jima on 19 February. She lowered landing craft and dispatched them to other ships of the division to ferry the assault troops to the beach. "Southampton" sustained her only casualties of the Iwo Jima assault during the initial landings when a mortar shell exploded close aboard one of her LCVP's and wounded the coxswain and a seaman. During the last two weeks in February, the attack cargo ship joined in unloading troops and supplies and embarking casualties from the fighting ashore. These operations were frequently interrupted by enemy air activity. On 1 March, "Southampton" sailed for the Marianas.