by Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions
There were other clues later in the war that seemed to indicate that Yama moto was not such an all-out carrier proponent. “For all his lip ser vice to the principle of the offensive and to naval air power, he still, perhaps subconsciously, visualized the battleship as the queen of the fleet.”26
Yamamoto recognized that there were risks involved in attacking Pearl Harbor. In particular, there was a significant chance that American land-based bombers would strike Kido Butai, possibly before the raid could be launched. Yamamoto in particular and the Imperial Navy in general believed in the lethality of land-based bombers against warships. Part of their Strategy of Interceptive Operations was predicated on the presumed capabilities of island-based medium bombers.
Yamamoto did not see how the Japanese carriers could deliver strikes during the Interceptive Operations without themselves being attacked by the American carriers. Because of the fragility of aircraft carriers, this would only result in the carriers’ mutual destruction with no subsequent advantage to Japan. What was needed was a way to strike the Americans outside the range of the American carrier-based aircraft.
Beginning in December of 1935 Yamamoto was assigned as the Chief of the Aeronautics Department of the Navy Ministry. He initiated the development of what was to become the G3M1 Type 96 Nell Attack Bomber.27 This was a breakthrough aircraft—a high performance twin-engine land-based monoplane that could carry a torpedo on exceptionally long-range missions. In its combat debut on 14 August 1937, a strike into China, the G3M1 Nell flew a round trip of 1,200 miles, an extraordinary achievement for the period.
With this range capability, airfields on the Mandates could be used as “unsinkable aircraft carriers.” In theory, aircraft could be transferred rapidly between airfields and concentrated ahead of the advancing US fleet. Massed medium bombers would strike well outside the enemy’s capability to retaliate.28 If the G3M1 Nell could eliminate the enemy carriers, then Japan’s carriers would have the freedom to strike the American fleet with impunity.
Yamamoto had considerable faith in the capabilities of this aircraft. A practical example was his reaction to the news that the British battleship Prince of Wales and battlecruiser Repulse had arrived at Singapore on 2 December 1941. These ships were a direct threat to several huge Japanese convoys about to depart for the invasion of Malaya. The stakes were high. His countermove was to deploy squadrons of G3M1 Nell medium bombers from the Empire to Indochina. Yamamoto did not redeploy any of his surface combatants or his reserve of battleships. He thought the medium bombers would be enough.29
The Japanese projected the effectiveness of their medium bombers onto the American aircraft, a tendency called mirror-imaging. Assuming the American bombers would have similar effectiveness as their own, they expected to lose at least one and likely more of their fleet carriers in any attack on Pearl Harbor. The risk to Kido Butai was accentuated by the distance to the nearest Japanese base. Towing a crippled carrier home would be out of the question—distance, winter weather, and a shortage of fuel, much less continuing American attacks, would scuttle any attempt. Any Japanese carrier sustaining significant engineering or floatation damage would have to be scuttled. With Japanese intelligence reporting 550 aircraft on Oahu,30 the Japanese carrier force could not be expected to escape unscathed.
The rather startling implication is that Yamamoto, portrayed as one of the most air minded of all the Japanese commanders, the “Father of Japanese Naval Air Power,” once the commanding officer of the fleet carrier Akagi, was willing to trade one, or half, or possibly all of his fleet carriers for a small proportion of the enemy’s battleship force. His operational orders to attack even if the carriers were detected 24 hours before the raid underline this willingness. In the actual event, when Japanese intelligence agents reported that all the American carriers had departed Pearl Harbor before the attack, Yamamoto was disappointed, but did not recall the attack. Sinking American aircraft carriers was a good thing in his mind, but not the overriding consideration. Yamamoto wanted a battleship, and was willing to pay in carriers.31
Even more startling was the fact that Yamamoto’s planners at one time seriously contemplated a one-way mission. Since all of Japan’s carriers did not have the unrefueled range to sail from Japan to Pearl Harbor and back, the planners considered sending in the carriers, launching the strike, recovering the aircraft, transferring the crews to other ships, and then scuttling those carriers without sufficient fuel for the return trip. One A6M Zero pilot related that “Genda-san told me that he was actually thinking that we would have to do a one-way attack in the beginning.”32 This option was dropped when means were found to provide the carriers sufficient fuel for a round trip, by overloading them with fuel at the outset and providing underway refueling.
Objective #2: Immobilize the Pacific Fleet
A second objective was to immobilize the US Pacific Fleet for at least six months. This was to prevent flank attacks interfering with the Japanese advance into the resource-rich areas in the far south. Was there actually a realistic threat to the Southern Advance by the US Pacific Fleet? If so, what would immobilize them?
Available Japanese Resources for the Southern Advance
The Japanese fleet was fully employed at the outset of the war. On 8 December 1941, the day of the attack west of the International Date Line, 93% of the Japanese large surface combatants and carriers were underway—ten of ten battleships,33 nine of ten carriers, eighteen of eighteen heavy cruisers, and eighteen of twenty light cruisers. There were no operational ships left in Empire ports other than one escort carrier loading aircraft to ferry forward, and a few small patrol ships.
The fleet’s reserve was the battle force, six battleships, two light carriers, two light cruisers, and ten destroyers, cruising south of Japan near the Bonin Islands. This force would remain in Empire waters until June of 1942.
The mobile striking force was a concentration of power: six fleet carriers, two fast battleships, two heavy cruisers, one light cruiser and nine destroyers. The Naval General Staff originally planned to have these carriers neutralize American air units in the Philippines, the most powerful enemy concentration of air power in the theater. Operating off the coast of Luzon, the carriers were to strike Clark Field and the surrounding complex of airfields, and afterwards provide direct support to the main invasion force at Lingayen Bay.
The Japanese would need all of their warships to successfully face the main American fleet, but much of their fleet would be committed as far away as the South China Sea supporting Army operations. It would take weeks for the Japanese Navy to concentrate enough force to oppose a move against the Marshall or Caroline islands, even if they cut free from their obligations to support the Army.
The Japanese advance south was a mountain torrent crashing into a desert plain. The surface forces of the US Asiatic Fleet consisted of only one heavy and two light cruisers with fourteen destroyers, while other Allied forces in the immediate invasion areas had only one battleship, one battlecruiser, one heavy cruiser, eight light cruisers (mostly obsolescent WWI types under 5,000 tons, suited only to protect convoys from auxiliary merchant raiders), with 13 destroyers.
There were other Allied forces scattered about—another two heavy cruisers and four light cruisers in outlying areas such as Sydney, Auckland, and South Africa. There were also a few cruisers and destroyers under repair or being refitted at Singapore, Sydney, and other locations. Some would be ignominiously towed to India to escape the Japanese advance.
BB = battleships; BC = battlecruisers; CA = heavy cruisers; CL = light cruisers; DD = Destroyers
Against this the Japanese invasion and covering forces (excluding the carrier striking force) totaled two fast battleships, sixteen oversized heavy cruisers, fifteen light cruisers and seventy-one destroyers. In addition, the Japanese would have a light carrier and ten seaplane tenders, along with land-based air. The Japanese could expect to have air superiority, if not air supremacy, early in the advance.
The J
apanese Southern Advance appears to have a surplus of surface combatants on a comparative basis, but this was incorrect. The ships’ mission was to hunt down the Allied surface ships, but they also had to protect the numerous invasion forces, each of which would need covering forces. The Allies might concentrate nearly anywhere. However, if the two Allied capital ships were eliminated, the excellent Japanese heavy cruiser fleet would dominate the theater.
In turn, the Allied opposition was weaker than the numbers suggest. Its assets were mostly aging or obsolescent ships and aircraft suffering under divided command. The different nations had different objectives and different ideas, mostly contradictory, regarding the employment of their forces.
For example, the Dutch, facing the invasion of their homes in Java, wanted to concentrate all forces and fend off the Japanese invasion fleets in a last-ditch, to-the-death defense of Java. In contrast, the British and Americans took a longer view, using their surface ships to protect their convoys from armed merchant raiders as they redeployed their ground and air forces. Their ships would be scattered between India and Australia and all points between. They sought to preserve their ships for a war that would continue long after Java fell. Ultimately, decisions on strategy and employment were made often for transitory political considerations rather than a unified strategic vision.
The ABDA (American, British, Dutch, and Australian) “Fleet” had no common doctrine, no common language, and could barely communicate with each other. Comparing the ABDA forces to a speed bump would be to exaggerate its power.
In the climactic major surface battle of the Southern Advance, the Battle of the Java Sea on 1 March 1942, only three months after the beginning of the war in the Pacific, Japanese forces were present in overwhelming strength. The Japanese had five carriers, four battleships, twelve heavy cruisers, six light cruisers, and 33 destroyers either engaged or within a day’s steaming of the battle. The ABDA coalition mustered two heavy cruisers, three light cruisers and nine destroyers—60 to 14 by ship count, nearly 10 to 1 in tonnage.
After only three months of fighting, the Japanese could have moved carriers, heavy cruisers and fast battleships to oppose any flank attack without unduly risking the Southern Advance.
Comparative Force Levels and the Pearl Harbor Attack
Battleships were the primary target in the Pearl Harbor attack.
The Japanese had to predict the American reaction if a given number of battleships were lost in an attack on the Pacific Fleet. The presumption was that with their fleet intact the Americans planned to advance; with some smaller fleet, the Americans would not. There are clues to how they may have developed their thinking.
Sometime after the Washington Naval Conference, the Japanese obtained information on the American Pacific strategy, Warplan ORANGE. The 1920s versions called for a rapid advance across the Central Pacific to seize the Mandates, recapture the Philippines and build an advanced base as a prelude to a fleet engagement. That plan would be executed with the forces allowed under the Washington Treaty, a 10:6 tonnage ratio in battleships and battlecruisers. So, the Japanese knew the Americans were planning an advance under the 10:6 ratio.
At the London Conference the Japanese proposed a 10:7 ratio. The Americans vigorously opposed this, an indication that 10:7 was the point where the Americans believed they could not defeat the Japanese with any surety. Consequently, the Japanese may have believed that an American trans-Pacific move would be forestalled if the Americans had 14 or fewer battleships.
(2) World Distribution of Battleships 6 December 1941
Yamamoto served as Japan’s Chief Delegate to the preliminary talks for the Second London Naval Conference, and as a delegate to the 1934 London Naval Conference. He was intimately familiar with the arguments concerning force ratios and their implications.
On 1 December 1941 the Japanese had their capital ships deployed as shown in the chart above. The Americans had 17 battleships in commission, 14 operational, two ships in overhaul, and one in refit, of which eight (seven operational and one in refit) were at Pearl Harbor.34 Thus, a loss of three battleships ought to draw down the American force low enough so that they would not risk a move west.
Within the six-month window for the Japanese offensive, three additional new 35,000-ton American battleships would be commissioned, of which one would complete workups and be available to participate in a Pacific offensive. An additional battleship would have to be destroyed at Pearl Harbor to compensate.
The Japanese could have used these considerations to calculate that they needed to incapacitate four battleships at Pearl Harbor.
Jumping ahead, appearance would indicate that the Japanese were correct in their estimates: after five battleships were taken out of the picture at Pearl Harbor, the Pacific Fleet did not sortie to relieve the Philippines. This has given the Japanese strategy a post hoc ergo propter hoc causality in the eyes of many historians. The Pacific Fleet did not move, therefore Yamamoto was right.
The Japanese set their objective at four battleships. This is confirmed from two statements. In the first, when asked why the attack on Pearl Harbor had not continued beyond the first two waves,
Fuchida also stated that the knowledge that the attack had accounted for four battleships was also a factor since it seems the Japanese high command regarded this number as a guarantee that the Americans would not be able to contest Japanese moves throughout the western and central Pacific.35
In another statement, when Genda briefed the commanders of Kido Butai on 23 November, he explicitly stated that “the primary objective of the attack is to destroy all US carriers and at least four battleships.”36 This substantiates the Japanese objective to destroy four battleships, a calculation that is a possible indication on how they arrived at that objective.
Note that Genda mentioned carriers before battleships. His personal objectives differed from Yamamoto’s, and, as will be seen, were significant in planning the attack.
Did the losses at Pearl Harbor really immobilize the Pacific Fleet? The truth lies in more than a simple hull count.
The Americans did not see 10:7 as any kind of tipping point in the balance of power. During discussions about revising the Washington Treaty, the Japanese diplomatic code had been broken, and American negotiators knew that if they firmly opposed the new ratio the Japanese had been instructed to acquiesce. Their hard stand was not due to a particular fear of increased Japanese numbers, or a perceived threshold between the forces associated with victory or defeat.
In fact, according to US Naval War College calculations, the US battleline maintained significant superiority over the Japanese battleline even after the Pearl Harbor losses. The Japanese battleline included four lightly-armored battlecruisers that were comprehensively rebuilt in the 1930s into “fast battleships.” Even with improved protection, their armor did not provide any zone of immunity against American battleship guns at less than 30,000 yards, making their gun turrets, magazines and engineering spaces vulnerable to knockout blows at the “hitting ranges” at which the battlelines would most likely fight. They were faster than the American battleline, so could choose to remain outside 30,000 yards where their deck armor was adequate, but at that range their hit rate would be miniscule and their ammunition would be expended to little effect. If they closed to hitting range they would be put out of action more quickly than any opposing American battleship.
So, American calculations showed the American battleline outclassing the Japanese battleline, even after Pearl Harbor. Warplan ORANGE could have been executed if their decision was solely based on their faith in defeating the Japanese in a battleline engagement.
Another aspect often ignored is that the Japanese were not only fighting the United States, but Great Britain as well. The chart above shows the worldwide distribution of battleships on 1 December 1941. The soon-to-be Allied nations had 24 operational battleships to oppose 16 Axis, 50 percent superiority. Five of the operational Axis battleships were Italian ships trapped by
geography, minefields, and airbases at the ends of the Mediterranean. They were technically outclassed by the British, and hampered by pusillanimous political controls, so these ships were effectively self-neutralized. Thus, the Allied advantage was greater than the numbers indicate, more like 24 to 11, or over two to one. On the other hand, four of the British battleships, the venerable “R” class, had severe operational restrictions and were the weakest of the British battleships, and certainly outclassed by the Japanese ones.
Since the destruction of Bismarck, the only operational Axis battleship with access to the Atlantic was Tirpitz. The battlecruisers Scharnhorst and Gneisenau were under repair at Brest, and so Great Britain, with nine operational battleships, looked to reinforce the Pacific. On 1 December 1941 that movement was in progress, with Prince of Wales and the battlecruiser Repulse en route to Singapore, and an “R” in the Indian Ocean.
Future trends were promising: two battleships would be coming out of refit (King George V and Revenge), two were completing workups (Duke of York and Ramillies), and one (Warspite) was in a US shipyard repairing battle damage and would be returning to service in February of 1942. Great Britain looked to have fourteen battleships and battle-cruisers in service inside the six-month window that Yamamoto felt was needed to complete the southern operations.
If six battleships were retained in home waters to counter the Germans’ three, and the situation in the Mediterranean maintained at the status quo, there would be five British battleships available for Far Eastern duties. Joined with the Americans’ 17 it would give the Allies a total of 22. If a Pearl Harbor strike took out all eight battleships there, 14 American and British battleships would remain, right at the cusp of what the Japanese feared could defeat them. So, if the Japanese failed to achieve a “clean sweep” at Pearl Harbor, based just on superficial numbers there would be sufficient Allied battleships and battlecruisers available to form a concentration that on paper ought to be able to defeat the Japanese fleet. And, as will be seen, the Japanese could not expect to take out all the battleships in the US Pacific fleet.
