On 28 February 1943, the convoy – comprising eight destroyers and eight troop transports with an escort of approximately 100 fighter aircraft – set out from Simpson Harbour in Rabaul.

The Japanese made no further attempts to reinforce Lae by ship, greatly hindering their ultimately unsuccessful efforts to stop Allied offensives in New Guinea.

Six months after Imperial Japan attacked Pearl Harbor in December 1941, the United States won a strategic victory at the Battle of Midway in June 1942.

[3][4] The ultimate goal of the Allied counter-offensives in New Guinea and the Solomons was to capture the main Japanese base at Rabaul on New Britain, later codified as Operation Cartwheel, and clear the way for the eventual reconquest of the Philippines.

Recognising the threat, the Japanese continued to send land, naval, and aerial reinforcements to the area in an attempt to check the Allied advances.

[7] After deciding to evacuate Guadalcanal on 4 January,[8] the Japanese switched priorities from the Solomon Islands to New Guinea, and opted to send the 20th and 41st Divisions to Wewak.

On the other hand, if the troops were landed at Madang, they faced a march of more than 140 mi (230 km) over inhospitable swamp, mountain and jungle terrain without roads.

The Allied Air Forces South West Pacific Area commander – Lieutenant General George Kenney – ordered an increase in reconnaissance patrols over Rabaul.

On 16 February, naval codebreakers in Melbourne (FRUMEL) and Washington, D.C., finished decrypting and translating a coded message revealing the Japanese intention to land convoys at Wewak, Madang and Lae.

Subsequently, codebreakers decrypted a message from the Japanese 11th Air Fleet to the effect that destroyers and six transports would reach Lae about 5 March.

[17] Kenney read this Ultra intelligence in the office of the Supreme Allied Commander, South West Pacific Area – General Douglas MacArthur – on 25 February.

[23] The results of the effort against the Japanese convoy in January were very disappointing;[10] some 416 sorties had been flown with only two ships sunk and three damaged; clearly, a change of tactics was in order.

Group Captain Bill Garing, an RAAF officer on Kenney's staff with considerable experience in air-sea operations, including a tour of duty in Europe, recommended that Japanese convoys be subjected to simultaneous attack from different altitudes and directions.

[28] In order for bombers to conduct skip or mast-height bombing, the target ship's antiaircraft artillery would first have to be neutralized by strafing runs.

"Pappy" Gunn and his men at the 81st Depot Repair Squadron in Townsville, Queensland, modified some USAAF Douglas A-20 Havoc light bombers by installing four .50-inch (12.7 mm) machine guns in their noses in September 1942.

An attempt was then made in December 1942 to create a longer range attack aircraft by doing the same thing to a B-25 medium bomber to convert it to a "commerce destroyer",[30][31] but this proved to be somewhat more difficult.

[35] The Japanese convoy – comprising eight destroyers and eight troop transports with an escort of approximately 100 fighters – assembled and departed from Simpson Harbour in Rabaul on 28 February.

This time, a route was chosen along the north coast, in the hope that the Allies would be deceived into thinking that the convoy's objective was Madang.

These two destroyers, being faster than the convoy since its speed was dictated by the slower transports, broke away from the group to disembark the survivors at Lae.

[49] On board one of the Beaufighters was cameraman Damien Parer, who shot dramatic footage of the battle; it was later included in the newsreel The Bismarck Convoy Smashed.

According to the official RAAF release on the Beaufighter attack, "enemy crews were slain beside their guns, deck cargo burst into flame, superstructures toppled and burned".

This was later justified on the grounds that rescued servicemen would have been rapidly landed at their military destination and promptly returned to active service,[58] as well as being retaliation for the Japanese fighter planes attacking survivors of the downed B-17 bomber.

[60] On 4 March the Japanese mounted a retaliatory raid on the Buna airfield, the site of a base that the Allies had captured back in January, though the fighters did little damage.

MacArthur issued a communiqué on 7 March stating that 22 ships, including twelve transports, three cruisers and seven destroyers, had been sunk along with 12,792 troops.

[1] Army Air Force Headquarters in Washington, D.C., looked into the matter in mid-1943 and concluded that there were only 16 ships involved, but GHQ SWPA considered the original account accurate.

[69] It was noted that the high and medium altitude attacks scored few hits but dispersed the convoy, while the strafing runs from the Beaufighters had knocked out many of the ships' anti-aircraft defences.

[71] The losses incurred in the Bismarck Sea caused grave concern for the security of Lae and Rabaul and resulted in a change of strategy.

We knew we could no longer run cargo ships or even fast destroyer transports to any front on the north coast of New Guinea, east of Wewak".

[73] The necessity of delivering troops and supplies to the front in this manner caused immense difficulties for the Japanese in their attempts to halt further Allied advances.

[77] In 1954, O. G. Haywood Jr., wrote an article in the Journal of the Operations Research Society of America in which game theory was used to model the decision-making in the battle.