Death of Admiral Yamamoto (1943): Operation Vengeance

The death of Admiral Isoroku Yamamoto on 18 April 1943 was one of the most remarkable episodes of the Pacific War. Guided by decoded Japanese messages, sixteen American P-38 Lightning fighters flew a long, low route from Guadalcanal and shot down the bomber carrying the commander of Japan’s Combined Fleet over the island of Bougainville.

The mission, known as Operation Vengeance, removed the architect of the attack on Pearl Harbor and dealt a heavy blow to Japanese morale.

Background

Isoroku Yamamoto, born in 1884, had studied at Harvard and served as naval attaché in Washington. He understood American industrial power and had opposed war with the United States. Once war came, however, he planned the surprise attack on Pearl Harbor in December 1941.

By 1943 Japan’s position had weakened. Its carrier force had been badly damaged at the Battle of Midway in June 1942, and in February 1943 Japanese forces withdrew from Guadalcanal after months of fighting. Yamamoto moved to Rabaul on New Britain to direct an air offensive in the Solomons and planned a tour of front-line bases to boost morale.

The decoded message

On 13 April 1943 a radio message detailed Yamamoto’s itinerary for 18 April: a flight from Rabaul to Ballale, a small island off Bougainville, with precise times. US Navy codebreakers in the Pacific intercepted and decoded it within about a day.

Admiral Chester Nimitz, commander of the US Pacific Fleet, weighed the risk that an attack might reveal that Japanese codes had been broken. He decided the chance to kill Yamamoto was worth it, and the mission was handed to Army Air Forces fighters on Guadalcanal. Accounts differ on how far the decision was discussed in Washington.

The interception

Only the twin-engined P-38 Lightning had the range for the flight, fitted with extra drop tanks. Eighteen aircraft of the 339th Fighter Squadron and other units at Henderson Field were assigned, led by Major John W. Mitchell. Two had to turn back, leaving sixteen.

Mitchell planned a roundabout route of more than 600 km flown just above the waves to avoid detection, timed by compass, airspeed and watch. Four pilots were picked as the “killer” section, among them Captain Thomas Lanphier and First Lieutenant Rex Barber, while the rest climbed to engage the escort.

On the morning of 18 April the Americans sighted two Mitsubishi G4M “Betty” bombers and six Zero escorts almost exactly as predicted. In a brief fight, both bombers were shot down. Yamamoto’s aircraft crashed into the jungle near Buin. The second bomber came down in the sea, and Vice Admiral Matome Ugaki, Yamamoto’s chief of staff, survived. One P-38 pilot, Lieutenant Raymond Hine, did not return.

Aftermath

A Japanese army search party reached the wreck the next day and found Yamamoto’s body. He was cremated, and his ashes were taken back to Japan. Tokyo withheld the news until 21 May 1943 and held a state funeral on 5 June. Admiral Mineichi Koga succeeded him as commander of the Combined Fleet.

To protect the secret of the codebreaking, the US did not officially publicise the mission at the time, and Japan did not conclude that its codes had been compromised.

Why Yamamoto was a target

For the United States, Yamamoto was more than a symbol. He was widely regarded as Japan’s ablest naval strategist, respected by his own officers and by his opponents. American leaders believed that no successor would match his skill or authority, and that his death would weaken Japanese planning as well as morale.

There was also an element of revenge for Pearl Harbor, reflected in the operation’s name. Some officers raised concerns about deliberately targeting an individual commander, but in wartime law he was a legitimate military target, travelling in a military aircraft through a combat zone.

The credit dispute

Who fired the fatal shots became a long and bitter dispute. Lanphier was initially credited, but Barber and other pilots contested this. Later study of the wreck and Japanese accounts led many researchers to favour Barber. The US Air Force officially gives shared credit.

Key people

• Isoroku Yamamoto (1884–1943), commander-in-chief of Japan’s Combined Fleet.
• Chester Nimitz (1885–1966), US Pacific Fleet commander who approved the mission.
• John W. Mitchell (1914–1995), mission leader and planner of the route.
• Rex Barber and Thomas Lanphier, pilots credited with the shoot-down.
• Matome Ugaki (1890–1945), chief of staff, who survived the crash of the second bomber.

Timeline

• 1941, 7 December: Japan attacks Pearl Harbor, an operation planned by Yamamoto.
• 1942, 4–7 June: Japanese defeat at the Battle of Midway.
• 1943, February: Japan evacuates Guadalcanal.
• 1943, 13–14 April: Yamamoto’s itinerary is transmitted and decoded.
• 1943, 18 April: P-38s intercept and shoot down Yamamoto’s aircraft near Buin.
• 1943, 19 April: A Japanese search party finds the wreck.
• 1943, 21 May: Japan announces Yamamoto’s death.
• 1943, 5 June: State funeral in Tokyo.

Why it matters

Operation Vengeance showed how signals intelligence could direct a single precise strike. It killed Japan’s most respected naval commander at a moment when the tide of the Pacific War, already turning at Guadalcanal, was running against Japan.