On 15 June 1943, "San Pablo" departed the United States West Coast and headed for the South Pacific Ocean. She embarked United States Marine Corps personnel and deck cargo at Espiritu Santo, then proceeded to Nouméa, New Caledonia. After offloading there, she went to Brisbane, Australia, to pick up the flight crews and aviation supplies, including spare parts and fuel, of Patrol Squadron 101 (VP-101), then returned to Nouméa to commence operations as tender and base for PBM Mariner and PBY Catalina flying boats conducting "Black Cat" night-fighting, air-search, and reconnaissance missions.