By April 1943, the fortunes of the Pacific War had already changed dramatically. Six months after the attack at Pearl Harbor, the Japanese suffered a catastrophic defeat at the Battle of Midway. The Imperial Navy had lost four of its frontline aircraft carriers and most of its experienced pilots. Unknown to them, their defeat was made possible because the U.S. had broken their secret JN-25 codes. This would later cost Japan its best admiral and the architect of the Pearl Harbor mission.

Admiral Yamamoto and his Lessons of America

Admiral Isoroku Yamamoto was the commander in chief of the Combined Fleet of the Japanese Imperial Navy. He had spent time in the United States and attended Harvard. He had traveled extensively, once hitchhiking across the country, and had observed America’s industrial might. While stationed in Washington as a naval attaché, he developed an affinity for poker as well as for America in general. Yamamoto was against the alliance between Japan and Germany and a potential war with the United States.

He once wrote to a member of the Japanese cabinet who called for war with America,

“Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians [who speak so lightly of a Japanese-American war] have confidence as to the final outcome and are prepared to make the necessary sacrifices.”

Yamamoto knew that in a long, protracted war, America’s vast natural resources and industrial might would crush Japan. So when the Japanese leaders insisted on war, he planned the attack on Pearl Harbor, hoping for a quick knockout of America’s fleet followed by a quick peace accord.

He had said, “I shall run wild considerably for the first six months or a year, but I have utterly no confidence for the second and third years.”

Operation Vengeance, the Assassination of Admiral Yamamoto
Admiral Yamamoto photographed just prior to boarding the aircraft that he was shot down in. (National Archives)

He had hoped that a preventive strike followed by a “decisive battle” could force the Americans to sue for peace. Nevertheless, for this to work Japan had to secure oil, which was always in short supply, otherwise, Japan could be strangled. 

Branch Rivalries Nearly Derail the Yamamoto Mission

A few months after Midway, America invaded the island of Guadalcanal. This would prove instrumental in the mission to get Yamamoto.

Through intercepted and decyphered Japanese radio traffic the Americans had learned that Yamamoto, in an attempt to boost morale after the Guadalcanal defeat, would fly on April 18 from Rabaul to Balalae Airfield, on an island near Bougainville in the Solomon Islands. He and his staff would be flying in a medium bomber (Mitsubishi G4M Betty of the Kōkūtai 705), escorted by six navy fighters (Mitsubishi A6M Zeros of the Kōkūtai 204). 

But, as described in the outstanding book Operation Vengeance: The Astonishing Aerial Ambush That Changed World War II by Dan Hampton, when the Americans learned of this, interservice rivalry and petty jealousies nearly sabotaged the mission. (SOFREP sat down and talked with Hampton about the mission.)

Contrary to public opinion, the Americans were not one big happy family: Marine and Army aviators hated each other. The rivalry got so petty that after the mission, two of the Army aviators were written up and recommended for the Medal of Honor, but Admiral “Bull” Halsey shot down the awards.

Operation Vengeance, the Assassination of Admiral Yamamoto
Thomas Lanphier (left) and Rex Barber (right) on Guadalcanal. (National Archives)

The Americans stationed at Guadalcanal would have to fly about 1,000 miles round trip to intercept Yamamoto and his flight. This was well beyond the range of the F4F Wildcat and F4U Corsair fighters of the Navy and Marine Corps units on the island. So the mission was turned over, reluctantly, to the Army pilots of the 339th Fighter Squadron, 347th Fighter Group, whose P-38G Lightning, equipped with drop tanks, had the necessary range.

The twin-engined Lightning had a 20mm cannon and four .50 caliber machine guns in the nose. Equipped with a 330-gallon drop tank, the aircraft would have enough fuel to fly to the area, engage the Japanese and return safely. Sixteen P-38G Lightnings were tasked with the mission. Four of the aircraft would attack the two Betty bombers and the rest fly cover to protect the force from the Japanese Zero fighters.

The Americans planned to take off at 0725 and fly a roundabout route to confuse Japanese radar. The plan was to arrive precisely when Yamamoto’s flight arrived at 0935. In a remarkable feat of dead reckoning, the Americans arrived at 0934, a minute early. Operation Vengeance would be led by Major John Mitchell.

Mitchell’s navigation was an underrated yet magnificent feat of piloting. As Hampton pointed out, Mitchell navigated for about 415 miles across the open ocean at an altitude of 50 feet, using a map, compass, and his wristwatch. As Hampton said, “arriving within a minute of the planned time of Yamamoto’s arrival was a supreme example of pilot skill.” 

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Nevertheless, the fuel situation for the Americans was stretched to the limit. Getting there and back with the drop tanks would only allow them about six minutes over the target at full power. 

Rex Barber Rises to the Occasion

The Americans spotted the Betty bombers just as they dropped down into view in a light haze. The P-38s tried to jettison their drop tanks and began to climb to intercept the bombers while paralleling their position.

The American pilots soon realized that instead of a sky full of Japanese fighters, the Japanese, hubristically believing they were invulnerable to American fighters at this range, had only six Zero fighters flying cover. It was then that they also recognized that there were two Betty bombers and not one. 

One contingent immediately turned to attack the escort fighters, freeing Rex Barber to attack the bombers. Barber dove on the fleeing bombers, one of which peeled off and dove for the jungle to escape. Barber lined up on the first bomber, which it turned out was carrying Yamamoto. With a quick devastating burst, he fired into the right engine and fuselage. Turning, he then hit the left engine. The Betty was chewed up by a slew of .50 caliber slugs and 20mm cannon fire. It began trailing heavy black smoke and rolled violently over, then pitched and crashed into the jungle. Yamamoto was dead. But Barber didn’t know that at the time. 

Barber then saw three Zeros who were lining up to get on his tail and firewalled his engines to get out to sea. It was then that he saw the second Betty bomber, skirting the tops of the jungle. He dove to attack it. 

He fired on the right engine of the Betty, which quickly emitted white vapor. Barber pressed home the attack and the Betty crashed into the ocean. He didn’t realize it, but that plane carried Vice Admiral Matome Ugaki, a member of Yamamoto’s staff. He and the crew survived and were rescued by the Japanese Navy later.

Desperately short on fuel, the Americans, after a brief skirmish with the Zeros, broke off for home. They landed with nearly dry tanks.

Thomas Lanphier, who wrongly claimed credit for Yamamoto’s kill, did a victory roll over the tower and broke security protocol by announcing on the radio, “That son of a bitch will not be dictating any peace terms in the White House.” His call on an open frequency could have revealed to the Japanese that their codes had been broken.

Later, Lanphier’s claim was disputed by the other American pilots as well as surviving Japanese pilots after the war. It was later proved that he was in no position to have shot down Yamamoto’s bomber and the credit for both bombers fell to Barber. 

Lanphier made no bones about wanting a political career after the war. On the other hand, Barber and Mitchell rose above the grandstanding and treated Operation Vengeance as just another combat mission. 

Operation Vengeance, the Assassination of Admiral Yamamoto
Barber’s P-38 “Miss Virginia” that he borrowed from Bob Petit for the mission returned with over 100 bullet holes. (National Archives)

The Japanese Remain Unaware That Their Codes Had Been Broken

The Japanese launched a rescue party for Admiral Yamamoto and he was found the next day. He had been thrown clear of the wreckage. He was strapped in his seat, his white-gloved hand still grasping his katana sword. He had suffered two shrapnel wounds, one in the shoulder and the other under his lower left jaw through his right eye killing him instantly.

The Japanese public wasn’t told of Yamamoto’s death until May 21. Trying to hide that they had broken the Japanese code, the Americans released a cover story saying that civilian coastwatchers in the Solomons had observed Yamamoto boarding a bomber and relayed the information by radio to American naval forces in the immediate area. The Japanese never believed that their codes had been broken by Americans who didn’t speak their language.

The lionization of Yamamoto by Japanese propaganda had put a huge target on his back. Those same propagandists ultimately cost Yamamoto his life. It is debatable whether the U.S. would risk losing the advantage of the Japanese codes if the sentiment wasn’t as strong against him.

Barber remained in the Air Force until his retirement in 1961. He died in July 2001 and was buried in Redmond, Oregon.