The cargo ship returned to battle during the Gilbert Islands invasion late November, landing equipment to aid in the successful assault on Tarawa. "Jupiter" then continued cargo operations until she was assigned to the 5th Amphibious Forces in April 1944 for the Marianas campaign. She departed Pearl Harbor 30 May and arrived in the Saipan assault area 15 June. She discharged her cargo despite constant enemy air attack and 10 days later proceeded toward Eniwetok.