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).

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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