On 15 September, "Mustin" served as primary fighter-director in the initial assault on Morotai, Netherlands East Indies, and after escorting reinforcements there from New Guinea, cleared Humboldt Bay on 16 October with reinforcements for newly invaded Leyte. Arriving on 25 October, "Mustin" departed the same day, escorting a convoy safely away from the Battle for Leyte Gulf. Escort operations among the bases of the western Pacific followed as "Mustin" gave distant support to the Philippines operation, before returning to Leyte Gulf on 25 November to join the local defense force under attack by enemy planes on 27 November. "Mustin" splashed three.