The Battle of the Bismarck Sea came after the allied victories of Milne Bay, the Kokoda Trail and Guadalcanal all of which were significant turning points in the South Pacific war with Japan.
The Battle of the Bismarck Sea is important as it ranks as the turning point in maturity, tactics, organization, support and logistics where an allied aviation force was able to completely dominate the air and sea in such force that a convoy shipping a Japanese division to Lae in New Guinea was decimated. From that point forward the United States 5th Air Force dominated the air and ocean such that no Japanese aircraft or shipping was able to move without the risk of being sunk or destroyed. Soon after the Australian and American aircraft in the South Pacific began wearing white tails and wings as they were more at risk of shooting each other down than Japanese. The dominance was total. Prior to late 1942 the attacks by the RAAF and 5th Air Force were disjointed and lacked sufficient numbers. They were constantly at risk from attack by Japanese fighters as well. Logistics were poor as was serviceability rates and aircraft often had to turn back for maintenance reasons. This was largely because the Australians and Americans had been bundled back from Singapore in a very short period and had lost a lot of men, machines and supplies in the process. The airmen of 1941 and early 1942 were fighting to keep a foot hold in New Guinea – which they achieved against great odds.
Additionally the American industrial machine was just starting to rev up to the kind of enormous output that it achieved in 1944/45. Supplies of aircraft, parts and ammunition were starting to flow into the South West Pacific [SWPA] despite the Germany first strategy of America, Britain and Russia. Up until this period the only heavy bombers in the South Pacific were American B17s which had been the sole strike force in New Guinea since the Japanese advance. The only medium bombers were an obsolete rag tag of Australian Hudson’s and Beaufort’s which had fought against impossible odds to carry out their tasks. In late 1942 more B17s arrived along with B24 Liberators. Douglas A20s started appearing along with the RAAF receiving Bristol Beaufighters from England. More importantly the North American B25 Mitchell started appearing in the theater. The Beaufighter and B25 were important. The Beaufighters quickly showed themselves to be an able weapon platform against Japanese shipping, airfields and army emplacements because of the enormous firepower in their nose and wings. The Beaufighter packed four 20 mm canons along with four .303 machine guns. When that firepower was focused on shipping it was devastating. Because of this realization the 5th Air Force equipped the B25s of the 3rd Attack Group with multiple .50 cal machine guns in the nose and in nacelles on the side. This gave the B25s eight machine guns to suppress anti-aircraft fire as they came in for low level attacks. Bombing doctrine prior to the Battle of the Bismarck Sea was for heavy and medium bombers to attack ships from height; often up to 7,500 feet. This was to stay away from fighters and anti-aircraft fire. The problem was that results for this were very poor as Japanese shipping would twist and turn making difficult targets for level bombing. The solution was skip bombing. This is where a medium bomber comes in at mast height level and drops the bombs so that they skip into the ship before exploding on a delayed fuse. This was practiced originally by the B17s on a rusted old shipwreck in Port Moresby but the medium bombers were more maneuverable and more effective with this tactic. Due to the breathing space being given by the victories in Milne Bay, Kokoda and Guadalcanal the 5th Air Force and RAAF started training in combined operations. Again on the rusty old wreck in Port Moresby but the tactic was for the Beaufighters to come in low and fast to strafe the ships and suppress any anti-aircraft fire. The skip bombers would come in immediately behind them while more medium and heavy bombers would do their bomb runs from a normal height. Lex MacAuley writes:
A practice mission against the wreck was finally flown on 28th of February, 1943. All the elements of a coordinated attack were included. The B17s went in first,bombing from 8,000 feet, followed by medium level B25s at 5,000 feet. RAAF 30 Squadron Beaufighters then went in firing their heavy armament of four 20mm cannon and six .303 machine guns, closely followed by Ed Larner’s B25s with .50 cal nose guns and 500 lb bombs.
This combined operational effort was what was used in the Battle of the Bismarck Sea two days later. The Japanese convoy itself was eight transport ships and eight destroyers as escort which left Rabaul for Lae. There it was intended the Japanese 51st Division would reinforce Japanese forces in New Guinea. There were multiple attacks against the convoy prior to the devastating skip bombing mission. Heavy bombers attacked the convoy from height and scored some hits on the transports, including sinking the Kyokusei Maru, but there was a flurry of tropical storms that hid the convoy for a day or so. Australian Beauforts also tried a torpedo run against the convoy but this produced no result. Eventually an RAAF “black cat” Catalina followed the convoy through the night marking its position and destination. The Japanese convoy decided to circle during the night so it would reach Lae in the morning. This decision meant that the convoy was exposed to attack through a spate of good weather the next morning in which the entire weight of the 5th Air Force and RAAF could be thrown against the convoy. Lex MacAuley writes:
First at the rendezvous point, the 71st Squadron, 38th Bomb Group began a wide, lazy circle at 5,300 feet as they waited for the armada to follow. The crews then saw a procession of air power greater than anything the Allied Air Forces had concentrated before in New Guinea. Captain W.S. Royalty described it as ‘an almost unbelievable number of planes’. B17s were moving into formation above the 71st; below came three separate flights of B25s; in formation and beginning to circle were Beaufighters and A20; the highest up were the P38s.
The Beaufighters went in first at low height to strafe the ships, especially the bridge which was the central control point, and suppress any anti-aircraft fire. The Japanese Destroyers mistook the Beaufighters for a torpedo attack and turned toward them which left the transports undefended by their anti-aircraft guns. The strafing run of one Beaufighter set the deck cargo of one transport alight which blew up and was noted by the other aircraft with a large dark smoke plume. Most of the anti-aircraft fire from the ships was aimed at the B17s which were bombing from on high and was not aimed at the low level bombers. After the Beaufighters the skip bombing B25s came in, strafing with their nose guns like the Beaufighters, but this time skipping bombs into the hulls of the ships. The results were immediate from the skip bombing tactic. Ships that weren’t sunk were immobilized by the bombing and strafing making them easier targets for the high level and medium bombers. At the end of this attack four Japanese destroyers that were undamaged picked up as many survivors as they could and headed to Lae. What remained of the convoy was four or five damaged transport ships, a sinking destroyer and one destroyer going around trying to pick up survivors. The second attack was not as large as the first because several squadrons could not get over the Owen-Stanley ranges due to bad weather. This included the RAAF Beaufighters, neither did the 39th Squadron USAAF with their P38s Lightnings. The force that was gathered was still large; including B17s, B25s, RAAF A20s and P38s. Bombing squadrons such as 22 Squadron RAAF which had done airfield suppression during the first attack were now freed up to attack the convoy itself. The remainder of the ships were either sunk or immobilized.
Those that remained were sunk over the next 24 hours by repeated bombing attacks. The day’s bombing had left numerous Japanese soldiers in the ocean after they had abandoned ship. The American and Australian airmen had been horrified by the stories of Japanese brutality to prisoners of war and injured soldiers. Airmen had seen Japanese fighters machine gun Australian and American airmen that had bailed out and were in parachutes. One of the consequences of this was that the Australian and American bombers strafed the Japanese soldiers in the water. The airmen found it distasteful but realized it needed to be done and that if it was a Japanese airmen in their shoes no mercy would be shown. The Battle of the Bismarck Sea was the first time the US 5th Air Force and RAAF achieved dominance over the air and sea in the SWPA and after the Bismarck Sea they never lost it again. A mix of superior machinery, superior tactics, superior organization and the will to bring it bear destroyed a Japanese division before it could set foot on New Guinea. From this point on Japanese shipping was always at threat of being sunk by Allied aircraft and the Japanese were swept from the skies and ocean.