Battle of The Bismarck Sea

The Battle of the Bismarck Sea (2–4 March 1943) took place in the South West Pacific Area (SWPA) during World War II. During the course of the battle, aircraft of the U.S. Fifth Air Force and the Royal Australian Air Force (RAAF) attacked a Japanese convoy that was carrying troops to Lae, New Guinea. Most of the task force was destroyed, and Japanese troop losses were heavy.

In December 1942, the Japanese Imperial General Headquarters decided to reinforce their position in the South West Pacific. A plan was devised to move some 6,900 troops from Rabaul directly to Lae. The plan was understood to be risky, because Allied air power in the area was strong, but it was decided to proceed because otherwise the troops would have to march through inhospitable swamp, mountain and jungle terrain without roads. On 28 February 1943, the convoy—comprising eight destroyers and eight troop transports with an escort of approximately 100 fighters—set out from Simpson Harbour in Rabaul.

The Allies had detected preparations for the convoy, and naval codebreakers in Melbourne and Washington, D.C. had decrypted and translated messages indicating the convoy's intended destination and date of arrival. The Allied Air Forces had developed new techniques that they hoped would improve the chances of successful air attack on ships. They detected and shadowed the convoy, which came under sustained air attack on 2–3 March 1943. Follow-up attacks by PT boats and aircraft were made on 4 March. All eight transports and four of the escorting destroyers were sunk. Out of 6,900 troops who were badly needed in New Guinea, only about 1,200 made it to Lae. Another 2,700 were saved by destroyers and submarines and returned to Rabaul. The Japanese would make no further attempts to reinforce Lae by ship, greatly hindering their ultimately unsuccessful efforts to stop Allied offensives in New Guinea.