Operation Vengeance was the American military operation to kill Admiral Isoroku Yamamoto of the Imperial Japanese Navy on 18 April 1943 during the Solomon Islands campaign in the Pacific Theater of World War II. Yamamoto, commander of the Combined Fleet of the Imperial Japanese Navy, was killed near Bougainville Island when his G4M1 transport aircraft was shot down by United States Army Air Forces fighter aircraft operating from Kukum Field on Guadalcanal.
The mission of the U.S. aircraft was specifically to kill Yamamoto, made possible because of United States Navy intelligence decoding transmissions about Yamamoto's travel itinerary through the Solomon Islands area. The death of Yamamoto reportedly damaged the morale of Japanese naval personnel, raised the morale of the Allied forces, and was intended as revenge by U.S. leaders, who blamed Yamamoto for the attack on Pearl Harbor that initiated the war between Imperial Japan and the United States.
The U.S. pilots claimed to have shot down three twin-engine bombers and two fighters during the mission, but Japanese records show only two bombers were shot down. There is a controversy over which pilot shot down Yamamoto's plane, but most modern historians credit Rex T. Barber.
Background
Admiral Isoroku Yamamoto, commander of the Imperial Japanese Navy, scheduled an inspection tour of the Solomon Islands and New Guinea. He planned to inspect Japanese air units participating in Operation I-Go that had begun 7 April 1943; in addition, the tour would boost Japanese morale following the disastrous Guadalcanal campaign and its subsequent evacuation during January and February.
Intelligence
On 14 April the U.S. naval intelligence effort code-named "Magic" intercepted and decrypted orders alerting affected Japanese units of the tour. The original message, NTF131755, addressed to the commanders of Base Unit No. 1, the 11th Air Flotilla, and the 26th Air Flotilla, was encoded in the Japanese Naval Cipher JN-25D, and was picked up by three stations of the "Magic" apparatus, including Fleet Radio Unit Pacific Fleet. The message was then deciphered by Navy cryptographers (among them future Supreme Court Justice John Paul Stevens); it contained time and location details of Yamamoto's itinerary, as well as the number and types of planes that would transport and accompany him on the journey.
The decrypted text revealed that on 18 April Yamamoto would fly from Rabaul to Balalae Airfield, on an island near Bougainville in the Solomon Islands. He and his staff would fly in two medium bombers (Mitsubishi G4M Bettys of the Kōkūtai 705), escorted by six navy fighters (Mitsubishi A6M Zero fighters of the Kōkūtai 204), to depart Rabaul at 06:00 and arrive at Balalae at 08:00, Tokyo time.
The U.S. Army Military Intelligence Service (MIS) was made up mostly of Nisei (second-generation Japanese Americans). They were trained in interpretation, interrogation, and translation of Japanese materials ranging from standard textbooks to captured documents. Information leading to Yamamoto's ambush was a significant MIS contribution in the Solomons campaign. MIS Technical Sergeant Harold Fudenna translated an intercepted radio message indicating the itinerary of Yamamoto. Although this message was first met with skepticism that the Japanese would be so careless, other MIS linguists in Alaska and Hawaii had also intercepted the same message, confirming its accuracy.
President Franklin D. Roosevelt may have authorized Secretary of the Navy Frank Knox to "get Yamamoto", but no official record of such an order exists, and sources disagree whether he did so. Knox essentially let Admiral Chester W. Nimitz make the decision. Nimitz first consulted Admiral William F. Halsey Jr., Commander, South Pacific, and then authorized the mission on 17 April. These U.S. commanders judged that the benefits of a successful mission included that Japanese morale would be negatively affected by news of Yamamoto's death and that Yamamoto's replacement would be less capable. When the issue was raised that the mission could reveal that the United States had broken Japanese naval codes, the commanders decided the knowledge could be protected as long as the true source of the intelligence was kept hidden from unauthorized American personnel and the press.
Interception
To avoid detection by radar and Japanese personnel stationed in the Solomon Islands along a straight-line distance of about 400 miles (640 km) between U.S. forces and Bougainville, the mission entailed an over-water flight south and west of the Solomons. This roundabout approach was plotted and measured to be about 600 miles (970 km). The fighters would, therefore, travel 600 miles out to the target and 400 miles back. The 1,000-mile flight, with extra fuel allotted for combat, was beyond the range of the F4F Wildcat and F4U Corsair fighters then available to Navy and Marine squadrons based on Guadalcanal. The mission was instead assigned to the 339th Fighter Squadron, 347th Fighter Group, whose P-38G Lightning aircraft, equipped with drop tanks, were the only American fighters in the Pacific with the range to intercept, engage and return.
339th Squadron Commander Major John W. Mitchell, already an ace pilot, was chosen to lead the flight. For better navigation, Mitchell asked for a navy compass, which was provided by Marine Corps Lieutenant Colonel Luther S. Moore and installed in Mitchell's P-38 the day before the attack. All of the P-38 fighters mounted their standard armament of one 20 mm cannon and four .50-caliber (12.7 mm) machine guns, and were equipped to carry two 165-US-gallon (620 L) drop tanks under their wings. A limited supply of 330-US-gallon (1,200 L) tanks was flown up from New Guinea, sufficient to provide each Lightning with one large tank to replace one of the small tanks. The difference in size put approximately 1,000 pounds (450 kg) greater weight on one side of the aircraft, but the tanks were located close enough to the aircraft's center of gravity to avoid serious performance problems.
Eighteen P-38s were assigned the mission. One flight of four was designated as the "killer" flight, while the remainder, which included two spares, would climb to 18,000 feet (5,500 m) to act as "top cover" for the expected reaction by Japanese fighters based at Kahili. A flight plan was prepared by the Command Operations Officer, Marine Major John Condon, but this was discarded by Mitchell who thought the airspeeds and time estimates were not best for intercepting Yamamoto. With several of his pilots assisting, Mitchell calculated an intercept time of 09:35, based on the itinerary, to catch the bombers descending over Bougainville, 10 minutes before landing at Balalae. He worked back from that time and drew four precisely calculated legs, with a fifth leg curving in a search pattern in case Yamamoto was not seen at the chosen point. In addition to heading out over the Coral Sea, the 339th would "wave-hop" all the way to Bougainville at altitudes no greater than 50 feet (15 m), maintaining radio silence.
Although the 339th Fighter Squadron led the mission, 10 of the 18 pilots were drawn from the other two squadrons of the 347th Group, (8 from the 12th FS and 2 from the 70th FS). The Commander AirSols, Rear Admiral Marc A. Mitscher, selected four pilots to be designated as the "killer" flight:
The remaining pilots would act as reserves and provide air cover against any retaliatory attacks by local Japanese fighters:
- Major John Mitchell
- Lieutenant William Smith
- Lieutenant Gordon Whittiker
- Lieutenant Roger Ames
- Major Louis Kittel
- Lieutenant Lawrence Graebner
- Lieutenant Doug Canning
- Lieutenant Delton Goerke
- Lieutenant Julius Jacobson
- Lieutenant Eldon Stratton
- Lieutenant Albert Long
- Lieutenant Everett Anglin
- Lieutenant Besby F. Holmes (replaced McLanahan)
- Lieutenant Raymond K. Hine (replaced Moore)
A briefing included the designated cover story for the source of the intelligence stating it had come from Australian coastwatchers, who supposedly had spotted an important high-ranking officer boarding an aircraft at Rabaul. Several historians say that the pilots were not specifically briefed on the identity of their target, but Thomas Alexander Hughes writes that Mitscher told the assembled pilots it was Yamamoto, to "provide additional incentive" to the fliers.
The specially fitted P-38s took off from Kukum Field on Guadalcanal beginning at 07:25 on 18 April. Two of the Lightnings assigned to the killer flight dropped out of the mission at the start, one with a tire flattened during takeoff (McLanahan) and the second when its drop tanks would not feed fuel to the engines (Moore).
In Rabaul, despite urgings by local Japanese commanders to cancel the trip for fear of ambush, Yamamoto's airplanes took off as scheduled for the trip of 315 miles (507 km). They climbed to 6,500 feet (2,000 m), with their fighter escort at their 4 o'clock position and 1,500 feet (460 m) higher, split into two V-formations of three planes.
Mitchell's flight of four led the squadron at low altitude, with the killer flight, consisting of Lanphier, Barber, and spares Besby F. Holmes and Raymond K. Hine, immediately behind. Mitchell, fighting off drowsiness, navigated solely by dead reckoning (speed and compass heading). This has been called the longest-distance fighter-intercept mission of the war.
Mitchell and his force arrived at the intercept point one minute early, at 09:34, just as Yamamoto's aircraft descended into view in a light haze. The P-38s jettisoned the auxiliary tanks, turned to the right to parallel the bombers, and began a full power climb to intercept them.
The tanks on Holmes's P-38 did not detach, and his two-man element turned back toward the sea. Mitchell radioed Lanphier and Barber to engage, and they climbed toward the eight aircraft. The nearest escort fighters dropped their own tanks and dived toward the pair of P-38s. Lanphier immediately turned head-on and climbed towards the escorts while Barber chased the diving bomber transports. Barber banked steeply to turn in behind the bombers and momentarily lost sight of them, but when he regained contact, he was immediately behind one and began firing into its right engine, rear fuselage, and empennage. When Barber hit its left engine, the bomber began to trail heavy black smoke. The Betty rolled violently to the left, and Barber narrowly avoided a mid-air collision. Looking back, he saw a column of black smoke and assumed the Betty had crashed into the jungle. Barber headed towards the coast at treetop level, searching for the second bomber, not knowing which one carried the targeted high-ranking officer.
Barber spotted the second bomber—carrying Chief of Staff Vice Admiral Matome Ugaki and part of Yamamoto's staff—low over the water off Moila Point, trying to evade an attack by Holmes, whose wing tanks had finally come off. Holmes damaged the right engine of the Betty, which emitted a white vapor trail, but his closure speed carried him and his wingman Hine past the damaged bomber. Barber attacked the crippled bomber, and his bullet strikes caused it to shed metal debris that damaged his own aircraft. The bomber descended and crash-landed in the water. Ugaki and two others survived the crash and were later rescued. Barber, Holmes and Hine were attacked by Zeros, with Barber's P-38 receiving 104 hits. Holmes and Barber each claimed a Zero shot down during this melee, although Japanese records show that no Zeros were lost. The top cover briefly engaged reacting Zeros without making any kills. Mitchell observed the column of smoke from Yamamoto's crashed bomber. Hine's P-38 had disappeared by this point, presumably crashed into the water. Running close to minimum fuel levels for return to base, the P-38s broke off contact, with Holmes so short of fuel that he was forced to land in the Russell Islands. Hine was the only American pilot who did not return. Lanphier's actions during the battle are unclear as his account was later disputed by other participants, including the Japanese fighter pilots. As he approached Henderson Field, Lanphier radioed the fighter director on Guadalcanal that "That son of a bitch will not be dictating any peace terms in the White House", breaching security and endangering the code-breaking program. Upon landing, one engine quit from fuel starvation. He immediately put in a claim for shooting down Yamamoto.
Aftermath
The crash site and body of Yamamoto were found on 19 April, the day after the attack, by a Japanese search-and-rescue party led by army engineer Lieutenant Tsuyoshi Hamasuna. The crash site was located in the jungle north of the coastal site of the former Australian patrol post and Catholic mission of Buin (which was re-established after the war several kilometers inland).