Planning the Attack on Pearl Harbor

A desperate gamble

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This post is the second in a mini-series on the attack on Pearl Harbor. You can find the first part here: We Only Ever Talk About the Third Attack on Pearl Harbor.

I found the inspiration for this story in Secrets & Spies: Behind-the-Scenes Stories of World War II; I found the book in an old bookstore and believe it is out of print, but Amazon has a few used copies (in the link above).


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Planning the Attack on Pearl Harbor

The successful Japanese attack on Pearl Harbor brought the United States into the war, but prevailing wisdom in Japan at the time said that the entrance was an inevitable eventuality. Many feared that a full-on attack by the United States had the potential to hobble Japanese war efforts elsewhere and even bring about a Japanese defeat. Thus, the attack was more of a desperate gamble to buy Japan time to secure a larger geography from which to extract natural resources and defend itself.

Japan’s strategy in the lead up to the December 7th attack was as impressive as the attack itself, providing a reminder that underestimating what you are up against, as the United States did with Japan at the time, can give the other side an advantage over you.

A Wartime Embargo

Japan relied heavily on imports from the United States to fuel its prewar industrial growth, most specifically on oil and metals. In the runup to World War II, tensions escalated between the two countries as Japanese aggression in China and Southeast Asia progressed.

Starting in 1939, the Roosevelt administration began implementing embargos on raw materials. The first embargoes were for aircraft construction materials, followed thereafter with increasingly critical metals until a final blow was dealt with an oil embargo in 1941. At the time, the United States was the source for 80% of oil imports in Japan, and without that trade-based lifeline, Japan was set to bleed down its store of oil reserves over the next twelve months.

Limited Options

Up until that point, Imperial Japan had relied on diplomatic routes to attempt to ease the vise of America’s embargo, but the restrictions on oil made it clear that the Roosevelt administration intended to punish Japan for its aggressiveness and reverse the gains Japan had made militarily. Violent conflict seemed inevitable at that point, with the Japanese military believing itself a superior people destined to control the lands it was invading while at the same time recognizing that the United State’s military strength could not be challenged head-on.

The military turned to the Commander-in-Chief of the Japanese Combined Fleet, Admiral Yamamoto, which was…

…ironical, for Yamamoto was a brilliant strategist who was flatly opposed to war with the United States. He had seen America's industrial might at first hand when he had studied at Harvard University, and later when he served as a naval attaché in Washington.

But Yamamoto was a robust nationalist and a Japanese to the very marrow of his bones. His love of Emperor and homeland was of volcanic ardor, and his warrior heart followed the traditions of the true samurai: duty first.

During the next phases of the war, Japan needed to secure access to the natural resources it was no longer able to procure from the United States. Its eyes turned southward — towards the Philippines, Malaya, and the Netherland’s East Indies (Indonesia today). At the same time, it knew that the United States would take action in response to such invasions, meaning that if Japan was to be successful…

…the U.S. Navy would have to be barred from southern waters, at least during the first critical months. How could this be done?

Yamamoto's approach to the problem was conditioned by both training and temperament. He was an aviation expert, a bold, original thinker and a gambler. He liked to quote maxims to drive home points in his speech, and one of his favorites was, "If you want the tiger's cubs, you must go into the tiger's lair." Inevitably his eyes were drawn to the tiger's lair at Pearl Harbor, Hawaii — where the U.S. Pacific Fleet was based.

Would it be possible to destroy this fleet before the [Japanese] strike at the southern regions began?

The hope was that by striking the United States first and disarming its Navy, Japan could benefit from a period of unchallenged military maneuvering in the Pacific, enough time to secure oil reserves in Indonesia and rubber from Malaysia. With these resources supporting the Japanese military, Japan hoped it would then be prepared for a prolonged engagement with the United States.

In January 1941, Yamamoto had already drawn up plans for an attack on the U.S. Naval base, ultimately proposing a near-replica of the attack Admiral Yarnell had used to defeat Pearl Harbor in 1932 during U.S. military wargames. He had also debated these plans with his inner circle. Even before the oil embargo, training exercises were being conducted and Japan’s fleet of vessels and aircraft re-organized in a way that would facilitate such an attack.

Despite these preparations, not everyone agreed with Yamamoto’s plan. Almost none of the other senior military men approved of it — calling it a reckless mission sure to fail, a strain on Japan’s already tight natural resources, or that it was foolish to rely on aircraft carriers as opposed to the strength of a seafaring navy.

The various disagreements even rose to the level of the Emperor himself and culminated in a bold move by Yamamoto in October 1941, when…

…he decided to send an emissary to the Naval General Staff for a showdown… he did not dally with niceties.

"Admiral Yamamoto insists that his plan be adopted," [ the emiisary ] said. "He has authorized me to state that if it is not, then he can no longer be held responsible for the security of the empire. He and his entire staff will have no alternative but to resign."

Finally, the Naval General Staff, acting as a body, sanctioned the Pearl Harbor attack. It was a great victory, but Yamamoto's position and influence in the Japanese Navy were unique. Not once did any member of the Naval General Staff consider going to war without Yamamoto at the helm of the Combined Fleet. "It was inconceivable," one of the admirals said later.

And with that, Yamamoto was given the green light to move forward, and preparations began in earnest.


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Espionage Kicked into High Gear

Immediately thereafter, the Japanese military doubled down on its already ongoing espionage efforts in Hawaii.

To lead information collection, Japan selected a relatively inexperienced 29-year-old former ensign in the Imperial Navy, Takeo Yoshikawa. It was this inexperience and lack of previously publicized accomplishment that allowed him to operate in Hawaii undetected. When combined with his work ethic and determination, Japan had a perfectly selected spy.

Yoshikawa plunged into work. He read the Honolulu papers from beginning to end each day, paying particular attention to shipping news and to social items about U.S. naval personnel. A daily stroll through Pearl City gave him a perfect view of Ford Island and its air strip… Here he could learn many things — Was the fleet going out soon? Was it taking on new supplies ? — by direct observation.

At night he also frequented bars popular with U.S. servicemen, standing them drinks and listening to service gossip, but seldom posing a direct question lest he attract attention to himself…

Hawaiian tourist trafficed offered Yoskikawa many opportunties… the cane fields at Aiea gave the best possible view of Pearl Harbor. Several times Yoshikawa dresed in laborer’s garb and studied the fleet from there, using a different cane field each time…

Holidays did not exist for him, and Sunday was just another day.

The information gathered through these efforts informed Tokyo of exactly where each ship was berthed, when it left the harbor, how long it took to leave, when it came back, the timing of air patrols, and other information important to a surprise attack. Most of this information was perfectly simple to obtain legally — one merely needed to watch and take notes.

Extensive Training

Building on the preparation Yamamoto had begun even prior to the approval of the mission, and at the same time that the U.S. government was fixing its eyes on the Atlantic, the Imperial Navy was drilling endlessly to prepare for a strike on Pearl Harbor. The attack would be unlike anything accomplished before, requiring coordination between hundreds of aircraft in a large formation — multiples of a normal attack force.

The task was formidable, the more so since the need for absolute secrecy made it impossible to tell the airmen what they were being trained for. Different types of aircraft — high-level bombers, torpedo planes, dive bombers, fighters — had to be welded into a coherent striking force capable of flying in perfect mass formation, not with just 40 or 50 planes but with several hundred. There was little time to accomplish this; time was running out every tick of the clock.

Yoshikawa smuggled maps back to Tokyo, detailing the size, location, and strength of every military establishment near Pearl Harbor. Using this map, on November 6, the Imperial Navy conducted a final dress rehearsal, duplicating the Pearl Harbor attack as closely as possible — 350 plans launched from 6 aircraft carriers, flew 200 miles across the ocean, and attacked target ships arranged as they would be on a Sunday morning at Pearl Harbor.

Hidden Through Misinformation

Throughout these preparations, Japanese diplomatic efforts in the United States continued. The Emperor had initially desired to declare war prior to an attack for the sake of honor, but his military advised that complete surprise was needed. Thus, up-and-until the final moment, Japanese diplomats kept up their foreign policy efforts without hinting at the impending attack.

Negotiations ongoing, Japan launched its attack fleet and began the steady march to Hawaii in late November 1941. In order to conceal the departure of such a large attack force…

…elaborate security measures were taken to conceal the fact from the Japanese people. To minimize the exodus of so many carrier planes, nearby air units were instructed to send extra flights over the air bases and towns so no sudden absence of planes would be noticed. All shore units were encouraged to grant leaves to as many men as possible, so that plenty of bluejackets would be visible on the streets.

The fleet itself was to travel in total radio silence. The volume of messages and instructions from Japan would necessarily increase once the fleet was under way, but the Navy had been building up dummy [radio] traffic for several weeks so that there would be no noticeable upsurge of radio activity.

Everything was to give the impression of "business as usual."

Gambling the Fate of a Nation

On the attacking force’s seventh day at sea, December 1st, radio instructions from Japan called for the fleet to “climb Mount Niitaka,” a code phrase indicating that diplomatic efforts in the United States had failed and that war was certain. A date had also been selected for the attack — Sunday, December 7th. At the same time, peace conversations were continuing in Washington despite Japanese resignation to war. The United States remained completely unaware.

As it received this message, miraculously, the Japanese fleet had just passed by the U.S. base at Midway without being detected. It pushed forward, preparing for combat.

On December 6th, shortly after midday, a pre-written message from the Japanese Emperor was shared with the crew, followed by Yamamoto’s own message: “The fate of the empire hangs on this one battle. Let every man-jack do his best.”

That night, Yamamoto’s chief of staff wrote in his diary, “What a tremendous thing it is to gamble thus the fate of a nation!”

The Attack

At 5:30 a.m. on December 7th, the first planes took off from the Japanese aircraft carriers floating north of the island. The first were reconnaissance aircraft, relaying back information on the location and status of Pearl Harbor’s fleet. They reported back what had been hoped — Pearl Harbor was unalert with their ships berthed in the harbor. Immediately thereafter…

…the entire launching operation was executed smoothly and swiftly. The first wave included 43 fighters, 49 high-level bombers, 51 dive bombers and 40 torpedo planes. Within 15 minutes from the moment the first aircraft left its mother ship, all 183 planes were in the air. It was the fastest launching on record. Adding the aircraft of the second wave, there would be 353 airplanes in the attack, the largest concentration of naval air power in the history of warfare to that time…

At exactly 7:49 the air waves crackled… "To-To-To !" It was the first syllable of the Japanese word for "Charge," and it meant that the first wave was now attacking. But it told nothing about the circumstances of that attack.

A few minutes later there was another message… "Tora, Tora, Tora l" (Tiger, Tiger, Tiger!) It was the prearranged code word for conveying the news that complete surprise had been achieved.

Unbelievably, Japan had launched a surprise assault on Pearl Harbor, arguably the world's greatest naval base at the time, and succeeded. 2,403 Americans were killed, 1,178 were injured, and nearly 200 U.S. aircraft were destroyed. This compares to Japanese losses of only 29 aircraft, five midget submarines, 129 killed.

Japan had prepared ferociously for such an attack, and it paid off. However, it didn’t have to be that way. The U.S. had seen this kind of attack before, but it just chose to believe it couldn’t happen again.


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Take care and have a great rest of the week,

— EJ


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