Takeo Yoshikawa and the Pearl Harbor Attack By 1941, two of the great Pacific powers were edging slowly and inexorably toward a state of war. The Japanese empire was expanding its frontiers, and to do so, it fielded a large military machine -- one which required large amounts of fuel in order to operate. Also hungry for oil was the industrial complex which underpinned the Japanese war effort. This presented the Japanese leadership with a problem: its vital resources were growing scarce, and its campaign against China only served to accelerate the rate at which oil was being burned. U.S. President Franklin Delano Roosevelt put up what he hoped would be a roadblock to further Japanese expansion in the form of an oil embargo and on the metals which were needed to sustain its campaigns. Japan relied on foreign imports for almost 95% of its oil supply.
Japanese assets and holdings in the United States were also frozen by presidential edict. The American stranglehold on Japanese resources, which was meant to defuse further aggression on Japan''s part, would instead have the opposite effect: it set off a ticking countdown to war. The Japanese leadership saw no other option. Their strategic oil reserves were rapidly dwindling. Unless a new supply could be secured, their ships would be unable to steam, their warplanes would be grounded, and their tanks would grind to a halt. The British and Dutch oilfields and refineries in the Pacific theater presented a possible solution, but it was highly likely that attempts by the Japanese to seize them by force would result in a military response by the United States.unless the American Navy could be taken out first. As 1941 wore on, the Japanese high command began to formulate plans for what it hoped would be a decisive strike against the United States Pacific Fleet at its base in what was believed to be a secure and well-protected anchorage: Pearl Harbor.
The fuse leading to war had already been lit, the Japanese knew. In the aftermath of the First World War, the United States had followed an isolationist policy. As the German and Italian armies began overrunning nation after nation across Europe and the Mediterranean, American public opinion remained staunch: no foreign wars or military entanglements. Despite the fact that Roosevelt saw the writing on the wall and attempted to aid the beleaguered British as best he could by supplying arms and materiel, in the political arena, his hands were largely tied. Despite this, however, the United States was beginning to re-arm and re-militarize. FDR recognized the dangers of an expansionist Japan and operated on the policy that it must be contained by any means possible. By the time war broke out in Europe, the United States'' armed forces were almost pitifully small by comparison to both its potential opponents and its allies, but as the storm clouds of a wider war began gathering on the horizon, the U.S.
began to convert an increasing number of factories to the production of arms and armaments. With each passing month, the Japanese leaders knew, the United States would only grow stronger. If a strike was not launched soon, delivering a devastating, knockout blow to American naval power in the Pacific, then any potential war might become un-winnable. Not everybody thought war with the United States was a good idea. The Japanese admiral Isoroku Yamamoto was very familiar with American culture, having served as a naval attaché in Washington DC and also studying at Harvard. During his time in the United States, he had traveled widely, conducting a shrewd assessment of the country''s people and its potential. He also learned to speak English and became a keen student of U.S.
military strategy and its capabilities. There was a misconception among some echelons of the Japanese political and officer corps that the Americans, as a people, were soft, lazy, and complacent; that they would have no will to fight, even if provoked. Isoroku Yamamoto saw them in a completely different light, and his subsequent warning to his superiors was stark: during the first six months to a year, he would "run wild" in the Pacific, he acknowledged, but after that, he could make no guarantees of victory. It would prove to be a prophetic announcement. From personal experience, he knew that the American industrial power base was too great for Japan (or any other nation) to compete with in the long term. War, if it came, must be fought on Japanese terms, and had to be won quickly -- or it could not be won at all. To Yamamoto would fall the responsibility of planning and carrying out the surprise attack -- one of World War II''s great ironies, considering that he had argued against making any attack on the United States at all. Yamamoto was not one to shirk from duty, however, no matter how unpleasant or hopeless it may have been.
Talks between the U.S. and Japan had continued throughout the year, but there were few illusions that genuine progress might be made by the diplomats. Even as Japanese emissaries met their counterparts at the negotiating table, their Navy was preparing for war. Hawaii was four thousand miles away from the Japanese islands. In addition to successfully sailing a naval carrier force to within striking distance of the American base, it would also be necessary to deploy spies to scope out the situation on the ground.and in the air. Enter Takeo Yoshikawa, a Japanese agent who traveled to Hawaii in the spring of 1941.
Yoshikawa was a graduate of the Japanese naval academy and had held an officer''s commission. He was on the career path to become a pilot when sudden and severe illness forced him to leave the service. Driven by a keen sense of duty to his nation, Yoshikawa did not take the medical discharge well but was able to serve it in a different capacity as an intelligence officer. He jumped at the opportunity to sign up when it was offered to him. Already an educated man with fluency in the English language, he was a natural fit for deployment to spy missions on Hawaii. A quick study, he set about reading everything that was available regarding U.S. naval fleet dispositions, absorbing information about everything from the smallest fighter plane to the largest battleship or aircraft carrier.
It didn''t take long before Yoshikawa memorized the defining characteristics of every vessel in the Pacific Fleet and was capable of identifying the highest value targets from every conceivable angle. His superiors in Japanese intelligence would want to know exactly which ships were in port when their attack force came calling. It''s a long-standing tradition that embassies and consulates also serve as centers of espionage, and the Japanese consulate in Honolulu was no exception. U.S. intelligence was fully aware of this, but spies got past their counter-espionage efforts anyway. It was here that Yoshikawa reported in March of 1941, ostensibly a junior-level embassy staffer. The supposed clerk was of sufficiently low rank that he drew little attention to himself.
After a brief period of orientation, Yoshikawa set about learning as much as he possibly could about the U.S. military presence in Hawaii. There was a lot to learn. Yoshikawa was an industrious young man, determined to gather as much practical intelligence as he could prior to the attack which was to take place nine months later. He operated under the alias of Tadashi Morimura. Driving by taxi and hiking his way across Hawaii, he gained an appreciation for the topography and the layout of the American installations. He was able to observe flights coming in and taking off from Hickam Field, and watched warships come and go from the anchorage at Pearl Harbor.
It was easy to count the number of vessels tied up and berthed at the various mooring quays. This was a simple matter of verifying what was already public knowledge, as ship movements were printed in local newspapers as a matter of course. Not all such military information was so readily available. In order to estimate and observe the depths in the harbor itself, Yoshikawa went out on a glass-bottomed boat tour and later pretended to fish in the shallow coastal waters in the vicinity of the U.S. base. One of the key concerns regarding any potential attack on Pearl involved the presence of anti-submarine/anti-torpedo nets. These hefty steel nets (or booms) were defensive measures that could be strung across the entrance of an anchorage, extending below the waterline, just waiting to ensnare any unsuspecting submarine that was trying to sneak in and get close to the American warships anchored there.
To allow friendly ships in and out, the net could be opened like a gate. The Imperial Japanese Navy (IJN) employed what were then called Midget Submarines, small submersibles crewed by two men, which could be deployed from a larger "mother sub." Each packed a pair of torpedoes and were ideally suited to the close-in work against big surface vessels such as the American carriers, battleships, and cruisers -- if they could get within range. The anti-sub net at Pearl extended some 35 feet below the surface, and the main channel was only 50 feet deep at its deepest point. The enterprising "Tadashi Morimura" confirmed the presence of such a net via the simple yet highly effective method of going for a swim and verifying it in person. Another key element was the lack of torpedo nets, designed to intercept any torpedoes dropped by attacking aircraft. It was believed that torpedoes needed about 75 feet of working depth after being dropped from an aircraft in order to work, and that the water at Pearl Harbor was therefore too shallow. This was a false assumption on the part of the U.
S. Navy, wh.