Posted on 1 Comment

Isoroku Yamamoto: Japan’s Admiral and Mastermind behind the Pearl Harbor Attack

Isoroku Yamamoto was the commander-in-chief of the Japanese Imperial Navy during the Second World War. He was a veteran of the Russo-Japanese war of 1905 and commanded the attacking fleet during the, for the Japanese disastrous, Battle of Midway and the Guadalcanal Campaign. But that’s not necessarily what he’s remembered for. Yamamoto was the mastermind behind the Pearl Harbor Attack on that fateful day, December 7th 1941. The infamous attack is engraved in the collective mind of Americans, and frankly large parts of the world. It directly led to the United States’ involvement in the bloodiest conflict the world has ever seen.

Isoroku Yamamoto (1884-1943)

Following the Pearl Harbor attack, the American press described Yamamoto as the ‘personification of the Japanese warlords’ eager to wage war against the United States. He was inherently anti-American, right? Well… no it is a bit more complicated than that in fact. 

  Yamamoto did not just study at Harvard University, but one of his roles during his career was as the Japanese naval attaché in Washington. He knew the United States, its culture, military and economic power. In fact, he was one of the highest-ranking commanders advocating against war, quite literally going against the Japanese Warhawks. In fact, during the late 1930s, the Japanese military issued 24/7 protection to Yamamoto, because they considered an assassination attempt from the pro-war nationalist camp a likely course of events, due to him being known as “Pro-American”. Yeah, this is the man that was literally the mastermind behind Pearl Harbor. That raises some questions: how did this come to be? 

But perhaps just as interesting as asking this question, is looking at Yamamoto’s eventual demise. Because in February 1943, the U.S. Office for Naval Intelligence managed to decode Yamamoto’s travel schedule. They realised they struck gold and arranged a secret operation with a killer squadron of Lockheed P-38 Lightning twin-engined fighter aircraft, tasked with intercepting his flight squadron. This secret mission became known as the aptly named “Operation Vengeance”: the mission to kill Admiral Yamamoto.

Early life 

Isoroku Yamamoto was born on April 4, 1884, as the sixth son of Samurai Sadayoshi Takano. He received education at the Imperial Japanese Naval Acadamy. He served on the cruiser Nisshin during the Russo-Japanese war of 1905, losing two fingers on his left hand during the decisive battle of Tsushima. It led to his rather funny nickname, ‘80-sen’ because a manicure cost ten sen per finger at the time. His superiors recognised him as a capable, ambitious and keen navy officer, sending him to the Imperial Naval Staff College. 

By 1916 he was a lieutenant commander when his parents passed away. Subsequently, the Yamamoto family adopted him, an adoption process which was customary at the time. In 1918, he married Reiko Mihashi and the couple had four children. Merely one year later, he left for the United States to attend Harvard University and study the oil industry. After graduation in 1923, he returned to Japan. He was promoted to Captain and began advocating the expansion of the Japanese Armoured Fleet, which the army disapproved of. Up until then, the military saw the Navy mainly as a transport branch for infantry. Yamamoto became fascinated by aviation after taking courses at the Kasumigaura Training Center. He soon became its director and became known for supplying the Navy with elite, well-trained pilots.

Yamamoto (1925)

He didn’t stay in Japan for long, though. In 1926 he was assigned as the official Japanese Naval attaché in Washington. This post gave Yamamoto the freedom to travel through the country and gain insights into their economic and military power and potential. During this time, the experiences he enjoyed greatly influenced his opposition to a German-Japanese alliance and war with the United States right before the war did break out.

The Brink of War

Yamamoto returned home from the United States in 1928. He briefly assumed command of the light cruiser Isuzu, before being appointed as commander of the aircraft carrier Akagi. In 1930 he was promoted to Vice-Admiral. He served as a special assistant to the Japanese delegation during the second London Naval Conference. Thanks to his diplomatic tact, or, according to a 1941 article in the San Bernardino Sun, his willingness to ‘torpedo’ the conference, he was one of the main factors in assuring Japan could expand its fleet according to the London Naval Treaty.

During subsequent years Yamamoto kept advocating for expanding the number of aircraft carriers, producing elite pilots, and ensuring a robust combined air and sea force for Japan. Although he still received scorn from the army for his ideas, slowly but surely they became a bit more widely accepted among other Naval officers.

Now, within this capacity, in 1933 he commanded the so-called Dai Ichi Koku sentai; or the First Carrier Division. This was an aircraft carrier unit of the Imperial Japanese Navy, consisting of two fleet carriers: Akagi and Kaga. Because of his previous successes in negotiating an expansion of the Japanese fleet, he became the Tokyo Naval Command spokesman at the London Naval Conference of 1934. Two years later he became vice-minister of the Navy, once again tirelessly advocating for a potent combined air and sea force, as he saw that as crucial for the Navy’s success. 

Meanwhile, within Japan, the Warhawk party grew, steering towards an all-out war against Japan’s neighbours and the United States to establish the Greater East Asia Co-Prosperity Sphere. Yamamoto was not part of this camp though. Because he tended to propagate a neutral stance and avoid war, the Japanese Warhawks attempted to eliminate him because they saw him as a pro-American traitor. Already in 1931 he vocally opposed the Japanese invasion of Chinese Manchuria and subsequent Second Sino-Japanese War. Another telling example was his response to the USS Panay Incident. In 1937, after Japanese aircraft bombed and sunk a U.S. gunboat, the USS Panay, on the Yangtze River, Yamamoto personally apologised to the U.S. Ambassador.

The army ordered him to be under protection 24/7 to prevent potential assassinations, which shows how controversial his stance was. Still, in August 1939 Minister of the Navy Mitsumasa Yonai promoted Yamamoto to the Combined Fleet commander-in-chief. Sources indicate one of Yonai’s motivations to do so was to save Yamamoto’s life, which, in his words, “could only be achieved by sending him out to sea.”

In September 1940 Japan, Italy and Germany signed the Tripartite Pact. It was Japan’s response to U.S. Congress voting to begin building new military ships, planes and the export embargo of some American goods to Japan. Yet joining the pact led to the United States placing an embargo on oil, steel, and iron exports to Japan. Sources indicate Yamamoto warned Japanese prime minister Fumimaro Konoe to not start a war with the United States, as Japan would not be able to compete with its economic and military power. During this time he was promoted to Lieutenant-Admiral. 

Yamamoto with staff of the combined fleet

As time progressed, Yamamoto began considering war against the United States inevitable. He concluded that protecting the logistical transport routes such as the Dutch East Indies’ oil supply would invariably lead to conflict. Against better judgment, Yamamoto had to begin planning a strategic offensive against the United States. He was the commander-in-chief of the Combined Fleet after all. He ordered the construction of two new aircraft carriers, convinced that in his words: “A swarm of ants will defeat the strongest snake.” An intercepted personal letter of him from late 1940 indicates that he resigned himself to war by this point. Although he personally may not have been in favour, he now did everything he could to ensure a Japanese victory. Realising time was of the essence as the empire could not sustain a prolonged war against the United States. 

Outbreak of War

Yamamoto figured that Japan’s only chance to win a war was to paralyse the U.S. Navy, mainly its aircraft carriers, in their own base before they had an opportunity to attack Japan. Having intricate knowledge of the U.S. economy and their military, he realised that if this failed Japan could, at most, hold out for a year before the tide of war turned. It led to him devising and planning the infamous surprise attack on Pearl Harbor, launching Japan into the global conflict costing countless lives. The entire strategy of the Pearl Harbor attack was contrary to traditional Japanese warfare. This time, the goal was to launch a surprise attack, paralyse the fleet and subsequently force a decisive battle. Once the battle was won, he hoped the American morale would be low enough to begin peace negotiations.

Yamamoto (1942)

And we all know what happened during that fateful day of December 7th 1941. Taking some caveats into account, the Japanese generally considered the attack to be a success. For the next six months, they rapidly expanded their territory in the Pacific Ocean. The Japanese commanders were surprised by the rapid advancement of their troops and the ability to conquer territories. 

Instead of forcing a decisive battle, as Yamamoto advocated, the Imperial General Staff decided to invade Birma, giving the United States a bit of breathing room. On April 18th 1942 the Americans launched the Doolittle raid on Tokyo. It proved the Japanese mainland wasn’t safe against U.S. aerial power. This swayed the Imperial General Staff to agree to Yamamoto’s plan to fight a decisive battle: the Battle of Midway. Commanding the entire Imperial Japanese Naval Fleet, Yamamoto figured Midway was the key to Hawaii’s defence. He hoped to lure the American fleet into a trap and to deal it a decisive blow. 

The Akagi and Kaga aircraft carriers he commanded years ago, were part of the fleet he deployed to Midway. Together with the Soryu and Hiryu, Japan’s vital aircraft carriers were all put in the ‘Midway basket’, if you will. Yamamoto sent a smaller fleet to the Aleutian Islands as a diversion. What he didn’t know was that instead of baiting the American fleet, they were baiting him. The Americans had broken Japan’s codes and received intel about his planned attack early on. 

During the battle, the Americans under the command of Admirals Frank J. Fletcher and Raymond Spruance managed to sink all four Japanese aircraft carriers. The battle resulted in an American victory, and a devastating Japanese defeat. From then on the Japanese operated on the defensive, with the momentum decisively shifting in the American favour.

Yamamoto continued attempting to conquer Samoa and Fiji. In order to set up a reliable base in the vicinity of these objectives, Japanese troops landed on Guadalcanal and constructed an airstrip. In August 1942 the Americans landed on the island, in what became known as the Guadalcanal campaign. Forced to fight for the island, Yamamoto could do nothing but endure the war of attrition that followed, losing face at the homefront, and losing many soldiers on the actual frontlines. 

Operation Vengeance

Now, a lot has happened since the attack on Pearl Harbor, by this point well over a year ago. But the Americans hadn’t forgotten. In order to understand what happened next, we have to take a look at Yamamoto’s base from where he operated. Rabaul, located on New Guinea, was one of the most important, if not the most important Japanese military base at that point in time. With well over 100.000 soldiers and navy personnel garrisoned, Yamamoto coordinated the Imperial Japanese Navy’s campaign from his headquarters there. It was basically a fortress. In addition to the military personnel, the island housed many anti-aircraft defences and an underground tunnels network. 

P-38 Lightning

In late February 1943, the Office of Naval Intelligence of the United States intercepted coded messages indicating Yamamoto would visit the Solomon Islands in April.  Not just that – but as they decoded more messages, they realised they acquired Yamamoto’s detailed travel schedule. He was going to fly from Rabaul to Balalae Airfield. Knowing he valued punctuality, the Office could estimate where he would be at all times, knowing the speed of Japanese transport aircraft and the fact he’d adhere to the schedule. 

Yamamoto’s trip commenced on April 18th. It was the perfect opportunity to take revenge for the Pearl Harbor attack and take out the man responsible for it. Under the command of Major John Mitchell, the Office began planning their operation. 

As for Yamamoto, his visit was planned just after the Japanese suffered their defeat during the Guadalcanal campaign. The idea behind Yamamoto’s visit was that it would boost the morale of the Japanese sailors and officers holding the Solomon Islands. Little did the Japanese know this trip would end up having the opposite effect.

That fateful day, April 18th, Yamamoto travelled from Rabaul, Papua New Guinea to Balalae Airfield on the Solomon Islands. Two twin-engined Mitsubishi G4M Betty aircraft carried both the Admiral and his crew. Six long-range fighter aircraft Mitsubishi Zeros escorted them. 

Meanwhile, on the American side, the Office of Naval Intelligence decided against using aircraft carriers. Positioning them in the area might have deterred the Japanese from continuing their trip as scheduled.  And if it didn’t deter them, the Japanese would indeed have sent their Naval fleet to destroy the carriers upon noticing. Because the operation required a bit more stealth, the Office decided upon using eighteen single-seated, twin-engined Lockheed P-38 Lightning fighter aircraft. 

Yamamoto a few hours before his death

The P-38s were outfitted with two extra fuel tanks, giving them a much-increased range compared to Wildcats and Corsairs. Of the eighteen, four P-38s were designated the so-called ‘Killer Group.’ These were tasked with taking out Yamamoto’s G4M, while the other fourteen P-38s covered the group against potential counter-attacks. After all, the operation took place close to Japanese air bases. The squadron did not exceed an altitude of fifteen metres above sea-level, in order to evade Japanese radar detection. 

On April 18th, 7:25 AM, the eighteen P-38s took off from Fighter 2 Airfield, on Guadalcanal. Two of them suffered technical difficulties not too long after take-off. Meanwhile, the Japanese squadron had taken off from Rabaul. They climbed to an altitude of around two kilometres. Thanks to the Japanese’s punctuality, the P-38s ran into the squadron at the exact right time: 9:35 AM. The four P-38s, part of the Killer Group, dropped their additional fuel tank and began climbing to the Zeros and G4M squadron’s height. Due to technical difficulties, one of the P-38s had to abandon its climb early on. With twelve P-38s acting as a cover squadron, the three P-38s continued climbing to take out the G4M. 

The sudden appearance of P-38s must have been a surprise to the Japanese pilots. After all, they were merely 15 minutes away from the Balalae landing strip. As soon as the Zero’s pilots saw them, they engaged in a dogfight. One P-38, piloted by Thomas Lanphier, fought the Zeros while the other two chased the G4M, one of them containing Yamamoto. Lieutenant Rex T. Barber shot down one of the G4Ms and narrowly avoided collision mid-air. The G4M crashed in the Bougainville jungle. 

Lieutenant Besby F. Holmes damaged the other G4M, but the job was eventually finished by Barber who shot the aircraft out of the sky. This one crash-landed in the water. One of the P-38s was shot down by a Zero. Now, both G4Ms crashed, but the commander of one of them survived. Aboard the G4M that crashed in the water was Vice-Admiral Matome Ugaki, who in fact survived the crash and was picked up by the Japanese Navy. Ugaki is fascinating in his own right for he survived the end of the war for Japan, only to become Japan’s final kamikaze pilot. I’ve created a video about Japan’s last kamikaze attack which I will link to at the end of this video.

But Yamamoto, well, he was aboard the first G4M that crashed into the jungle. And he did not survive the crash. Japanese films depict Yamamoto as stoically meeting his end, although he was more likely struck by a P-38 Lightning’s ammunition, striking his aircraft’s right-wing, causing it to crash. As such, it is generally assumed he died before the plane crashed, being directly hit in the head. If you would like to see a film about Yamamoto’s life, consider watching the 2011 Japanese war drama film Isoroku, depicting his career and actions during the war.

Yamamoto’s funeral

Operation Vengeance was a definitive success, although if Yamamoto had been in the other plane, he would have survived the attack. Thanks to this mission, Pearl Harbor’s mastermind met his end due to a well-executed secret operation by the Office of Navy Intelligence.

The killing of Admiral Yamamoto was poetic justice from the American perspective. Precisely a year previous the Americans bombed Japan during the Doolittle Raid, proving the Japanese mainland was within reach. And exactly one year later they again struck a decisive blow against the Japanese.

The wreckage of Yamamoto’s plane still lies amidst the Solomon jungle. It is accessible, but only by trekking through thick vegetation and swampy grounds. A Japanese search-and-rescue party recovered Yamamoto’s remains the next day. His remains were cremated, and he was given a state funeral on June 5, 1943, over a month after his death. When studied, Yamamoto lived a life that appeared to be full of contradictions during an incredibly challenging time in history. As for Japan, it would take a little over two more years before they finally surrendered after the dropping of two atomic bombs by the United States. 

1 thought on “Isoroku Yamamoto: Japan’s Admiral and Mastermind behind the Pearl Harbor Attack

  1. […] As for Curda, he survived the Second World War. But, he was tracked down and arrested in 1947. His motives were largely inspired by either greed or fear for the safety of his own family. He was sentenced to be executed for collaboration with the Nazi occupiers and high treason. Operation Anthropoid remains the only successful assassination attempt of a high-ranking Nazi official, even though many such attempts took place preceding and during the Second World War. Still, the U.S. did manage to successfully assassinate the Japanese Admiral Isoroku Yamamoto. I have written an article about that here. […]

Leave a Reply