I expressed my opinion to the Chief of Staff, “I understand, Sir. However, since the main element of our plan will be the torpedo attack, I would like to share the objective of this training with Lieutenant Murata. He is the commander of the Akagi’s torpedo bombing squadron, and it will be critical to have him engaged in the torpedo attack in shallow seas.”
“You said Murata. I approve.” The Chief of Staff nodded and added, “In any event, at the earliest opportunity, I intend to call a meeting of our heads of aviation and explain our objective to them. In order to attain the fastest possible improvement of our required skills, it will make a difference once they understand. Anyway, I think we have no time to lose, and I am counting on you, Commander.”
13
Water Depth 12 Meters
For our air attack on the US Pacific Fleet at Pearl Harbor at the very inception of the war, we assumed that the enemy capital ships berthed there would be four aircraft carriers and eight battleships. These were the main targets of our air attack squadrons, and the main force assigned to the attack task force was a total of 90 planes of Type 97 Carrier Attack Bombers. The 90 planes were divided into a level bombing squadron of 50 planes and a torpedo bombing squadron of 40 planes. The level bombing squadron was to be placed under my direct command, and the torpedo bombing squadron was to be led by Murata.
In those days, the Japanese Navy adopted a probable-odds bombing calculation method because the targeting accuracy of level bombing was not so good. Under this method, each of the nine bombers in a formation would drop their bomb according to the sighting of the guide-bomber plane at the head of the formation, trying to secure a hit of at least one out of the nine bombs by sandwiching the target within the impact zone. This method was highly inefficient because it required a lot of planes to ensure the required killing shots. However, there was no other choice because, based on experience, not a single hit was secured by any of the nine planes if they were not flying in formation.
Furthermore, in order to sink enemy carriers or battleships, the intention was to have our armor-piercing bombs penetrate the target’s deck and, with a delayed fuse, explode at the targeted ship’s bottom. Since we had no inventory of armor-piercing bombs for use at Pearl Harbor, as an emergency measure, we made them by shaving the 16-inch shells of the Nagato-class battleships. By testing the piercing power of modified 800-kilogram armor-piercing bombs, it was proved that dropping the bombs from an altitude of 3,000 meters would be sufficient to penetrate the armored decks of the US battleships. It was decided that a five-plane formation—instead of nine—would be sufficient to achieve our probable-odds bombing objectives given that we would be aiming at non-moving targets below from the low altitude of 3,000 meters. Accordingly, the 50 planes of the level bombing squadron were organized into 10 sub-squadrons.
In level bombing, the lower the altitude, the higher the probability of hitting the target. However, the enemy anti-aircraft fire would hit better as well. It is a matter of balance, but in war time, we have to hit the targets with our bombs instead of shrinking from enemy fire. The altitude of 3,000 meters is where the enemy fire is concentrated the most, and level bombing at this altitude requires a lot of guts. But we had more than enough guts on our side. Thus, the level bombing squadron practiced day in and day out trying to improve their skill by dropping exercise bombs from an altitude of 3,000 meters on a target in the shape of an Oklahoma-type battleship, which was drawn with lime on the Navy bombing range at Shibushi Beach.
However, the problem was the torpedo bombing practice. The water depth of 12 meters still remained an obstacle, and the sinking degree of launched torpedoes needed to be reduced to 10 meters. Forty planes of the torpedo bombing squadron carried 800-kilogram torpedoes. Lieutenant Murata, commander of the torpedo bombing squadron, was the top expert of torpedo attacks, and he thought long and hard to find a solution for the shallow water torpedo attack. The objective was a sinking degree of 10 meters, and he consequently reduced the launching altitude to 10 meters, almost touching the surface of the sea. At the same time, he changed the torpedo’s launching position to a nose angle of zero with the plane’s velocity at 160 knots, aiming at skipping the launched torpedoes at a shallow angle.
Unrelenting practice went on every day. In order to recover the training torpedoes, they were launched in the deep waters of Kagoshima Bay, and the sinking degree was checked by a recorder attached to the torpedo head. Meanwhile, the skill of the fliers improved day by day until the sinking degree stabilized within 20 meters. Just one more stretch to go, but the performance improvement stopped there. No matter how many times we repeated blood-shedding practice drills, the sinking degree refused to go down further. Finally, among the torpedo fliers, there were some mutterings, “Why don’t they compromise with a 20-meter sinking degree? Where on earth is there a fleet that berths in such a shallow place with a depth of only 10 meters?”
They had reason to complain. There should be no fleet that berths in shallow waters of only 10 meters depth. While fliers knew that the practice was intended to attack berthed ships, nobody realized yet that it was Pearl Harbor. Besides, we tried hard not to give a single hint to them that would give away our secret.
We knew perfectly well that if we simply revealed to them that the target was Pearl Harbor, their muttering would have disappeared in an instant, making them exert several times more effort, but it was not allowed yet. While we admired their efforts to have come so far as to have attained a sinking degree of 20 meters, there was no effective difference compared to a sinking degree of 60 meters. There was no compromise possible with the target of 10 meters, not even by one meter.
One day, my Naval Academy classmate, Lieutenant Commander Takeshi Naito came to see me at Kagoshima Base. He was also a close friend from the days when we both aspired to be aviators.
“Hey, I thought you went to Germany.”
“Right. I was there for one year, more or less, but I was called back.”
Naito was the assistant military attaché to the German Embassy, and on his way back he stopped over at the Taranto Naval Port with orders to conduct a survey on what was referred to as the Taranto Incident. On November 11, 1940, more than a dozen seaplanes from two squadrons of the British Royal Navy made a surprise attack on the Taranto Naval Port and sank three Italian battleships anchored there using torpedoes. The sea where the torpedoes were launched had a depth of 14 meters, and it was reported that the seaplanes launched their torpedoes almost touching the sea surface. Naito gave me details of the battle.
And when he finished talking, I asked him, “Who told you to come to tell me this story?”
“It was Mr. Fukudome of the General Staff.”
“Hmm,” I gave a groan. It was Rear Admiral Shigeru Fukudome, Head of the Operations Bureau.
“You know why you came here to tell me the story?” I asked Naito, to which he said “No.”
“It’s OK if you don’t know. I will not tell you myself, but you’ll come to know. But thanks for telling me this useful story. It helped.” I thanked Naito again. So, there was actually a successful case of launching torpedoes in shallow waters. I was encouraged by this battle case. I was elated that we would not lose to John Bull’s British Navy.
Around that time, we were provided with torpedoes fitted with stabilizing fins using gyroscopes to improve the launched torpedo’s entry angle into the sea surface. In actual use, they performed very well, almost reaching the targeted sinking degree of 10 meters. But the performance was still uneven, and we wanted one more month of practice to gain more confidence.
However, we were already running out of time. The Fleet Command Center unofficially announced the completion of all practices on or close to November 10th. We were already in early November, leaving us fewer than 10 days. I was upset because I wanted to give to each flier—all 40 planes—the opportunity to actually launch one torpedo to boost their confidence before we finished our practice.
I made this request to the Co
mmand Center, but their response was that it was out of the question. Their reasoning was if they agreed to my request, it would reduce the supply of torpedoes for the expeditionary operation to Hawaii. In the end, they let me move forward but limited the practice launch to just three torpedoes. I was discouraged with that number, but there was no choice. I decided to select three pilots with daily proven skill levels— first, second and third grade. We did a location survey for 12 meters water depth at Kamoike Beach. We took the tides into consideration as well, put down white and red flags and had the three pilots launch their torpedoes. Lieutenant Murata and I watched from above in a plane flown by Murata.
The first torpedo was launched by the pilot with the first grade rating. The torpedo left a long and straight white wake. Then, the next torpedo was launched by the second grade pilot. It was also beautiful. Lastly, the pilot with the third grade tried, but, as anticipated, the torpedo got stuck in the seabed, emitting a lot of bubbles.
As we got off the plane, Murata appeared to have broken down. Tapping his shoulder, I encouraged Murata. “Look, Bussan. Long time ago, on the occasion of the Battle of Ichi-no-Tani, Minamoto no Yoshitsune approached the Hiyodorigoe Pass with his army. The hills appeared too steep to run down. Then Yoshitsune asked the guide if he had ever seen horses coming down the hills. The reply was that while he had never seen horses coming down, deer could go down. Hearing this, Yoshitsune said, ‘Both horses and deer have four legs,’ and he kicked two horses downhill. One fell, injured, but the other one went down safely. He looked back at his soldiers and said, ‘If half of you should reach the enemy, the victory is ours. Follow me!’ And Yoshitsune led the brave assault descending the steep hills and attacked the enemy from behind.
“Thus, the battle of Ichi-no-Tani ended up in total victory for Yoshitsune. In that situation, Yoshitsune bet that his chance of victory was one out of two. Now, we are betting that our chances are two out of three. We have a better chance. Just like the downhill assault at Hiyodorigoe, the surprise attack at Pearl Harbor will be spearheaded by the torpedo bombing squadron. If two-thirds of the 40 launched torpedoes should make it through, that makes 27 torpedo hits. It will be enough to kill the US Pacific Fleet. Bussan, it’s ‘You guys, follow me!’”
Murata was taken aback, and his depressed face returned to a smile.
Incidentally, a short while later, Murata was promoted to Lieutenant Commander effective November15th, and Genda and I were also promoted to Commander.
And as it turned out, according to materials published by the US officials after the war, this two-thirds success ratio was correct. On the very day of the Pearl Harbor air attack, while five out of the 40 planes of the torpedo bombing squadron were shot down, 27 torpedoes launched by the surviving bombers hit their targets, with the following results. By ship, the number of torpedo hits was:
Battleship
USS Nevada
1
Repair Ship
USS Vestal
41
Battleship
USS West Virginia
7
Battleship
USS Oklahoma
5
Battleship
USS California
3
Cruiser
USS Raleigh
1
Target Ship
USS Utah
5
Total
27
After the Pearl Harbor air attack, the Pearl Harbor Investigation Commission was convened many times, and the official report, which was massive, allocated many pages to the torpedo attack by the Japanese air force. It stated that the biggest damage to the US ships on December 7, 1941 was caused by the torpedoes launched by the Japanese bombers. It also added that those torpedoes were specially devised to meet the mode of attack executed by the Japanese air force on that day.
However, with regard to the issue of why the Pacific Fleet did not extend torpedo defense nets, the official report stated that, according to professional opinions at the highest levels in the United States, the likelihood of such an attack had been considered impossible—until the Japanese air force proved that attack by torpedo bombers could be accomplished easily in shallow waters like Pearl Harbor and even under the restrictive conditions of short distances from combat targets. Therefore, they concluded that the Pacific Fleet’s commanders could not be accused of failing in their duties.
Here I saw all the hard toil and labor of the Japanese torpedo bombing squadron rewarded—trying to make the impossible possible and sending torpedoes to their targets at a water depth of 12 meters.
14
Daikairei Dai-Ichi-Go—Order
No. 1, Naval Department,
Imperial Headquarters
Imperial Headquarters had already been established, and the Navy General Staff was incorporated as the Naval Department of the Imperial Headquarters. It was not long after that they were involved in conceptualizing the operations of the expedition to Hawaii as proposed by Admiral Yamamoto. This drove them into a frenzy as they prepared for the abruptly introduced operation.
Initially, the Command Center of the First Aviation Fleet, headed by Commander Nagumo and Chief of Staff Kusaka, was against the expedition to Hawaii. However, once the decision was made to proceed, they were fully occupied with preparations for the operation. A key problem was increasing the cruising capacity of the ships that would be participating in the attack. As was widely known, the foundational principle of operations of the Imperial Japanese Navy was based on the assumption of a decisive battle in the Western Pacific. In addition, because of the constraints imposed by the Naval Treaty, the Imperial Navy was compelled to fight with only 70% of the US Navy’s fighting capacity. Therefore, the General Staff developed operational plans with distinctive characteristics in order to secure victory.
They intended to maintain the option to fight or not to fight against the US Fleet by taking advantage of the superior speed of our ships. On the other hand, the US Navy’s war plans against Japan were based on trans-oceanic offense-oriented operations. Therefore, they emphasized cruising capacity. In designing fighting ships, if cruising capacity is emphasized, superiority in speed is reduced. As a result, the maximum speed of the US capital ships remained at 19 knots at most. In contrast, under the assumptive condition of a showdown in the Western Pacific, the Japanese Navy did not have to worry about cruising capacity. They concentrated on superior speed, and 30 knots2 was required even for capital ships. Thus, the Imperial Navy had a chance to win the planned-for decisive fleet battle by securing the option of fight or not to fight. However, in the case of the long expedition to Hawaii, our lack of sufficient cruising capacity emerged as an obstacle.
Therefore, there was no other way but to replenish our fuel while cruising on the ocean, but it would not be easy if the sea was rough. In addition, the choice of which route to take was an issue. If we needed accompanying tankers for our fuel supply, we were going to be a grand fleet of more than 30 ships. And if such a grand fleet should push forward across the Pacific Ocean 3,000 nautical miles to Hawaii, there would be no place to hide. There also would be no chance of winning if the air attack on Pearl Harbor was not a surprise attack. The General Staff was in utter confusion.
Kusaka, however, was not panicked at all. He ordered Lieutenant Commander Risaburo Sasabe to check the routes taken by all merchant ships in the world that crossed the Pacific Ocean over the past 10 years. Despite his dull appearance, Staff Officer Sasabe was intelligent, and he presented his report based on his survey of all the records of the world’s shipping companies. According to the report, it was noted that there had not been a single merchant ship that passed the northern latitude of 40 degrees during the winter months, which included December. More important, the northern latitude of 40 degrees is in the middle of the patrol zones from the US bases at Midway and the Aleutians. Kusaka decided to choose this course. However, there was a reason that not a single ship took this course: the northern latitude of 40 degr
ees coincided with an area of turbulent seas in the Northern Pacific during the winter period. If rough weather continued every day, fuel replenishment on the ocean could not be implemented. Kusaka seemed to have worried about these conditions a great deal, but he did not change his tough stance. Although refueling on rough seas would be very difficult, there could be no compromise regarding the need for secrecy of the attack plan. The only option was to do all that we could possibly do with respect to refueling on the ocean. On this point, the admirals of the fleet were convinced.
In the meantime, what emerged as my headache was the issue of participation of the carriers of Carrier Division 5, the Zuikaku and the Shokaku. These two ships had just been commissioned, and the degree of proficiency of the carrier-based air squadron was very insufficient. The inclusion of Carrier Division 5 to the First Aviation Fleet, which now consisted of six carriers, added fighting capacity in terms of the number of planes. However, in terms of quality, their squadron could not keep pace with the air squadrons of Carrier Divisions 1 and 2. Besides, there was no time left to quickly improve their proficiency. If those with different levels of proficiency should engage together in a group action, the group would be inevitably forced to adjust to the lowest level of proficiency. This was the source of my distress.
For That One Day: The Memoirs of Mitsuo Fuchida, Commander of the Attack on Pearl Harbor Page 7