Admiral Isoroku Yamamoto, commander of the Imperial Japanese Navy, scheduled an inspection tour of the Solomon Islands and New Guinea.

On 14 April the U.S. naval intelligence effort code-named "Magic" intercepted and decrypted orders alerting affected Japanese units of the tour.

The message was then deciphered by Navy cryptographers (among them future Supreme Court Justice John Paul Stevens[1]); 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.

[3] 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,[4] and sources disagree whether he did so.

[6] 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.

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.

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.

[9] 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.

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: A briefing included the designated cover story for the source of the intelligence stating it had come from Australian coastwatchers,[7] who supposedly had spotted an important high-ranking officer boarding an aircraft at Rabaul.

[13] 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.

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.

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.

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.

[15] 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 retrieval party noted Yamamoto had been thrown clear of the plane's wreckage, his white-gloved hand grasping the hilt of his katana, his body still upright in his seat under a tree.

These more violent details of Yamamoto's death were hidden from the Japanese public, and the medical report whitewashed, this secrecy "on orders from above" according to biographer Hiroyuki Agawa.

The announcement said that the admiral was killed in April while directing strategy on the front lines and had "engaged in combat with the enemy and met gallant death on a war plane.

[17] At this point, U.S. officials had not disclosed anything about the operation, and the American public first learned of Yamamoto's death when the 21 May Japanese statement was covered in the news.

[16] The Japanese account was augmented by American writers noting that Yamamoto's purported claim that he would dictate peace terms to the United States from a seat in the White House was now sure not to happen.

[22] Regardless of any cover story, intelligence officials in Great Britain were upset by the operation; not having suffered the Pearl Harbor attack themselves, they did not have the same visceral feelings towards Yamamoto and did not think that killing any one admiral was worth the risk to Allied codebreaking abilities against Japan.

[24] The American public did not learn the full story of the operation, including that it was based on broken codes, until 10 September 1945 after the conclusion of the war, when many papers published an Associated Press account.

[27] Part of one wing has been removed and is displayed, on permanent loan, at the Isoroku Yamamoto Family Museum in Nagaoka, Japan.

Lanphier claimed in his report that after turning to engage the escort Zeros and shooting the wings off one, he had flipped upside down as he circled back towards the two bombers.

As a result, Major John Mitchell's nomination for the Medal of Honor was downgraded to the Navy Cross; this was the same award subsequently presented to all the pilots of the killer flight.

Yanagiya also affirmed that none of the escorting Japanese fighters were shot down, stating that only one was damaged enough that it required a half day of repair at Buin.

"[29] In May 2006, Air Force Magazine published a letter by Doug Canning, a former pilot of the 347th Fighter Group who flew on Operation Vengeance (he escorted Holmes back to the Russell Islands).

Canning agreed that Barber had a strong case for his claim citing the testimony of Yanagiya who saw Yamamoto's "Betty" crash 20 to 30 seconds after being hit from behind by fire from a P-38.

In spite of criticism from Barber and other surviving pilots from the mission, Lanphier continued to claim credit for downing Yamamoto until his death in 1987.

"[31] Rice commented in 1993, "Historians, fighter pilots and all of us who have studied the record of this extraordinary mission will forever speculate as to the exact events of that day in 1943.