Action off Bougainville

The Action off Bougainville was a naval and air engagement on the South Pacific Theater of World War II near Bougainville, Papua New Guinea on 20 February 1942. In the engagement, a United States Navy aircraft carrier task force on its way to raid the Imperial Japanese military base at Rabaul, New Britain was attacked by a force of land-based bombers of the Imperial Japanese Navy. The U.S. task force was commanded by Admiral Wilson Brown and the Japanese aircraft forces were under the command of Eiji Gotō.

In the ensuing engagement, the Japanese air group was almost completely annihilated, losing 15 of 17 bombers sent to attack the American carrier group. The US lost only two fighters in defense, and no ships were damaged. As a result of the loss of surprise, however, the Americans retired without raiding Rabaul as originally planned. Because of the heavy losses in bombers, the Japanese were forced to delay their planned invasion of New Guinea, giving the Allies more time to prepare defenses against the Japanese advances in the South Pacific.

Prelude
Following the capture of the port of Rabaul during the battle of Rabaul, Japanese forces proceeded to turn it into a major base. Concerns grew in the allied command that with the fall of Rabaul the San Francisco-Australia sea lane supply line would be threatened and ordered the supply line to be patrolled. Admiral Chester William Nimitz and Admiral Brown devised a plan to solve the threat on the supply line by attacking the newly captured Rabaul. Task Force 11 (TF 11) and ANZAC Squadron were tasked with undertaking the raid. Unfortunately, ANZAC Squadron lacked the fuel oil to head north while TF 11 sailed north to its launching point north-east of Rabaul planned for 21 February.

Battle
TF 11 with USS Lexington (CV-2), 450 mi from the harbor at Rabaul, detected an unknown aircraft on radar 35 mi from the ship at 10:15. A six-plane combat patrol was launched, two fighters being directed to investigate the contact. These two planes, under command of Lieutenant Commander Thach shot down a four-engined Kawanishi H6K4 "Mavis" flying boat about 43 mi out at 11:12. Later, two other planes of the combat patrol were sent to another radar contact 35 mi ahead, shooting down a second "Mavis" at 12:02. A third contact was made 80 mi out, but reversed course and disappeared.

Rabaul having been alerted of the presence of U.S. naval forces in the area, alerted Vice Admiral Shigeyoshi Inoue at the Imperial Japanese Fourth Fleet headquarters in Truk, who ordered an initial air strike to be conducted from Rabaul and also ordered the Cruiser Division 6, consisting of the heavy cruisers JAPANESE CRUISER Aoba, JAPANESE CRUISER Furutaka, JAPANESE CRUISER Kinugasa, and JAPANESE CRUISER Kako to intercept TF 11.

Seventeen Japanese Mitsubishi G4M1 "Betty" bombers of the 4 Kokutai took off from Vunakanau Aerodrome, Rabaul to attack TF 11. Admiral Brown, having lost the element of surprise, decided to break off the attack against Rabaul and started to retire from the area. At 15:42, a jagged vee signal was detected on radar, but the contact then was lost, but reappeared at 16:25 47 mi west. Nineteen F4F-4 Wildcats from Lexington were sent to intercept the incoming targets. Of the nine incoming "Betty"s from 2nd Chûtai of 4 Kokutai, at this time five had already been shot down.

At 16:49, a second formation of "Betty"s were detected by radar only 12 mi out, on the disengaged side of the task force, completely unopposed, from 1st Chûtai of 4 Kokutai. Lexington only having two Wildcats, piloted by Lieutenant Marion Dufilho and Lieutenant Edward O'Hare, left to confront the intruders, flew eastwards and arrived 1500 ft above eight Bettys nine miles out at 17:00. Dufilho’s guns jammed and leaving only O'Hare to protect the carrier from the enemy formation in V formation flying very close together.

O'Hare employing a high-side diving attack accurately placing bursts of gunfire into a "Betty"'s right engine and wing fuel tanks; when the stricken craft of Nitō Hikō Heisō Tokiharu Baba (3rd Shotai) on the right side of the formation abruptly lurched to starboard, he ducked to the other side of the V formation and aimed at the enemy bomber of Ittō Hikō Heisō Bin Mori 3rd Shotai on the extreme left. When he made his third and fourth firing passes, the Japanese planes were close enough to the American ships for them to fire their anti-aircraft guns. The five survivors managed to drop their ordnance, but all 10 551 lb bombs missed. O'Hare's hits were so concentrated, the nacelle of a "Betty" literally jumped out of its mountings, after O'Hare blew up the leading Shōsa Takuzo Ito's "Betty"'s port engine. O'Hare believed he had shot down five bombers, and damage a sixth. Lieutenant Commander John Thach arrived at the scene with other pilots of the flight, later reporting that at one point he saw three of the enemy bombers falling in flames at the same time.

O'Hare had destroyed only three "Betty"s: Nitō Hikō Heisō, Tokiharu Baba's from 3rd Shotai; Ittō Hikō Heisō, Susumu Uchiyama's (flying at left wing of the leading V, 1st Shotai); and the leader of the formation, Shōsa, Takuzo Ito's. This last (flying on the head of leading V) "Betty"'s left engine was hit at the time it dropped its ordnance. Its pilot Hikō Heisōchō Chuzo Watanabe tried to hit Lexington with the damaged plane. He missed and flew into the water near Lexington at 17:12. Another two "Bettys" were damaged by O'Hare's attacks. Ittō Hikō Heisō Kodji Maeda (2nd Shotai, left wing of V) safely landed at Vunakanau aerodrome and Ittō Hikō Heisō Bin Mori was later shot down by Lieutenant Noel Gayler when trying to escape 40 mi from Lexington.

Aftermath
As a result of the loss of surprise, Brown canceled the planned raid on Rabaul and retired from the area. Because of the high losses in bomber aircraft, the Japanese postponed their impending invasion of Lae-Salamaua, Papua New Guinea from 3–8 March 1942.

Two "Mavis" flying boats were also shot down which were shadowing the U.S. force, as well as two other Japanese scout aircraft lost in operational accidents while participating in the day's action. The U.S. lost two fighters to defensive gunfire from the bombers, but one pilot survived, while no damage was inflicted on the U.S. warships. U.S. Navy pilot Edward O'Hare was awarded the Medal of Honor for his actions.