Flying from bases in eastern New Guinea No. 100 Squadron flew reconnaissance patrols and anti-shipping and bombing missions against the Japanese in the Solomon Islands and New Guinea mainland. Eight aircraft from the squadron participated in the Battle of the Bismarck Sea, during which the squadron conducted a torpedo-bombing mission. It was not successful in sinking any ships in this battle, though, and from March 1943 it operated solely in the level bombing role. Later, in September 1943, the squadron flew anti-submarine patrols in support of amphibious landings around Lae. On 4 October, ten Beauforts made a low-level attack on the Japanese airfield at Gasmata, with three aircraft being shot down. A surfaced submarine was attacked and heavily damaged in St George's Channel on 18 October. The squadron bombed a bridge over the Anwek River in November as part of an air offensive over New Britain and the same month moved to Goodenough Island.