After completing training, No. 78 Squadron was deployed to the combat zone north of Australia in October 1943. From November that year until September 1944 the squadron supported the advance of the Allied ground forces through western New Britain and the north coast of New Guinea by attacking Japanese positions, providing fighter protection for recently established beachheads, and escorting Australian and United States bombers. From late 1944 until mid-1945 it operated against Japanese positions and shipping in the eastern Netherlands East Indies. The squadron took part in the Borneo campaign during the final weeks of the war. No. 78 Squadron was reduced to a cadre after it returned to Australia in December 1945, but received new aircraft in 1946 and undertook training exercises until being disbanded in April 1948.