"Harrison" departed 22 August for New Guinea, where she supported with gunfire Rear Admiral Barbey's landing on Morotai Island 15 September. After helping to establish this important air base, the destroyer joined a larger task force at Humboldt Bay and departed 13 October for one of the largest operations of the war, the invasion of the Philippines. "Harrison" arrived off Leyte 20 October and delivered accurate shore fire for the assault forces during the initial stages. She then assumed escort duties in already crowded Leyte Gulf until returning to Humboldt Bay 23 October.