Attack on Pearl Harbor (4 page)

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.
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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,

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.

There were significant impediments to concentrating the American and British battlelines. Should Singapore fall the British would not have a base from which to operate more forward than some Australian port. British battleships did not have the endurance of the kind demanded by central or south Pacific operations, and did not have the afloat logistics support—fuel and spare parts—to allow them to effectively maneuver in the vast Pacific. The Americans had plans for operations from remote anchorages, and likely could accommodate a British contingent as a substitute for damaged American ships. Fuel supply would be critical: 20 to 30 oilers would be required to support such a force, against the 11 available to support the entire Pacific Fleet. And indeed, as will be seen, it was not losses that defeated American aspirations to move west, but the steely hand of implacable logistics.

There are a number of practical things that also made such a concentration unlikely, things like a lack of a shared doctrine, incompatible command and communications, and the political willingness of the British to risk their battleships against what they saw as a secondary opponent. The chances that an effective union of the British and American fleets in the Pacific could have been realized in 1942 are miniscule.

Yamamoto treated the two fleets as independent entities. His attack on Pearl Harbor did not have the capability to draw down the total number of Allied battleships to where a combined Allied fleet could not defeat the Japanese battleline, but that was not needed. Yamamoto had the additional advantage of interior lines, should any British battleships operate out of Singapore or Java or Australia. But had the British and Americans advanced, even independently, he might have been faced with the necessity of splitting his battleship fleet. He could not be strong everywhere at once.

The next chart shows the world situation one month later, on 1 January 1942. The numbers have changed significantly. Of the eight battleships at Pearl Harbor, two were total losses and three were sunk with salvage operations likely to take six months or more. The remaining three lightly-damaged ships were sent to the West Coast for repairs and modernization. The British lost
Prince of Wales
and
Repulse
to Japanese torpedo bombers, and
Queen Elizabeth
and
Valiant
were crippled in Alexandria harbor by mines laid by Italian frogmen. In one disastrous month the Allies lost four battleships permanently with another five side-lined for long-term repairs, a loss of 38% of their operational force.

Against these losses,
King George V
and
Ramillies
completed their refits and returned to the operational forces. The Axis had the Italian
Vittorio Veneto
damaged by submarine torpedoes.

Overall, the Allied advantage evaporated. As the chart shows, Allied battleship strength was concentrated in the Atlantic, which will be discussed later.

(3) World Distribution of Battleships 1 January 1942

Had it not been for some fortuitous, unpredictable help, Yamamoto’s Combined Fleet could have been placed in a very difficult situation.

Consider the situation where the Pearl Harbor attack incapacitates four of the Pacific Fleet battleships, and the four British battleships had not been sunk at Alexandria and off Singapore. The Americans could have concentrated thirteen battleships at Pearl Harbor, while the British could have had five or more battleships in the Far East. This would have presented Yamamoto with a difficult strategic situation: split the fleet of reserve battleships, or concentrate against one and give the other enemy force freedom of action?

Had this situation developed, a likely possibility, by initiating war against both the Americans and British, the Japanese were placing their fleet in a perilous situation even with a successful Pearl Harbor strike.

The Expected Nature of the American Threat

There were four types of threats the Japanese faced from the Pacific Fleet, divided by time frame: an immediate threat (one to three months after war began), two intermediate-term threats (four to twelve months), and the longer-term threat.

Immediate Threat

Any immediate threat would come from the Pacific Fleet. Not counting ships in long-term overhaul, this would consist of three carriers, eight battleships, twelve heavy cruisers, nine light cruisers, and forty destroyers.
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This force could mount raids on the Marshall and Caroline islands within weeks of the initiation of hostilities. It would be unlikely they could do more—they would be tethered to their base for fuel, as the demand for tankers for the European war cut the resources available to the Pacific Fleet.

However, the Japanese apparently did not consider that the Americans would be limited by such constraints, a manifestation of their famous neglectful attitude towards operational logistics. On the other hand, logistics constraints on the Pacific Fleet could be changed. If Hitler had not declared war on the United States, America might have declared war against Japan only. Many consider such an occurrence inconceivable, but it not only was conceivable, it happened—for three days, between when Congress declared war on Japan on 8 December, and Hitler declared war on the United States on 11 December. Had Hitler not twitched and allowed American rage to remain pointed to the Pacific, the “Europe First” strategy might have gone by the wayside, and the Pacific Fleet might have received a flow of resources looking more like those described in Warplan ORANGE (the original war plan for a war against Japan) rather than RAINBOW 5 (the American war plan for coalition war against the Axis).

The Japanese had received assurances from Hitler in April of 1941 that Germany would declare war on the United States, assurances repeated in November and again at the beginning of December. Hitler was anxious to bring the Japanese Navy into the war on the Axis side, while the German Navy was pressing Hitler to expand the submarine offensive beyond the restrictions imposed by American neutrality. So the Japanese could attack, secure in their assumption that the United States Navy would be engaged in a two-ocean war.
³⁸

Intermediate-Term Threat: The Pacific Fleet

After the war began the Americans were expected to gather auxiliaries and supply ships to allow deeper penetrations into the western Pacific. The Japanese believed they would also gather ground forces for a move directly to the Philippines. This was what the strategy of Interceptive Operations planned to defeat. The Japanese fleet could equal or exceed the Americans in battleships and battlecruisers, and outnumber them in carriers, cruisers and destroyers.

If this move occurred before units covering the Southern Advance could reinforce the battle fleet, the Japanese would only have the reserve battle force and
Kido Butai
to oppose the Pacific Fleet.

CV = fleet carriers; CVL = light carriers; BB = battleships; BC = battlecruisers; CA = heavy cruisers; CL = light cruisers; DD = Destroyers

In conventional terms, the Japanese would have the inferior force, being severely outnumbered in cruisers and destroyers. They would have a decided advantage in carrier decks, almost three times that of the enemy, but at this time carriers were still an unknown factor—it was not known how lethal they would prove against surface ships, and how rapidly their air groups would be depleted in combat operations. The Japanese did not have a reserve of carrier-qualified aircrew. When the carriers
Shokaku
and
Zuikaku
joined the fleet, the Japanese had to scrape the bottom of their training programs and raid schools and staffs to put together the air groups, and even then the two ships’ air groups were considered to be only marginally qualified when they were dispatched on the Pearl Harbor raid.

Some theorists of the time believed that carrier air strikes at sea would suffer 50% attrition per strike. If so, the Japanese air groups would have been decimated to ineffectiveness after only two or three raids. The advantage in carrier numbers was not seen as the overwhelming force overmatch that a modern observer (knowledgeable of the subsequent carrier battles in the Pacific) would assess.

The Japanese would be badly outnumbered in cruisers, and it was from the cruisers that the Japanese pinned a good portion of their hopes toward wearing down the Pacific Fleet with massed torpedo attacks.

Overall, this was not a confrontation the Japanese preferred.

Ideally, the Japanese would want the American counteroffensive to come after the Southern Advance had concluded. This would not only free more fleet units for the encounter, but also the Japanese conquests would be “in hand” if a peace conference should begin immediately after the Japanese repulse of the Pacific Fleet. If the Pearl Harbor attack was successful in demoralizing the American public, Yamamoto believed the Americans should be brought to the negotiating table immediately after the fall of Singapore.
³⁹

Intermediate-Term Threat: Pacific and Atlantic Fleets Joined

A second intermediate-term possibility was that the Americans would wait to commence their movement until after the Atlantic and Pacific Fleets had joined.

Congress had refused to build up to the Washington Treaty limits, so in 1936, when the Treaty lapsed, the two navies were near to a ratio of 10:7. That would rapidly change. From the beginning of 1936 to the end of 1940 the Japanese added seven cruisers and had three battleships under construction, while the Americans added twelve cruisers and had ten battleships under construction, with many more ships planned. The Japanese fleet might be able to encounter the Americans at close to the Treaty ratio in 1941, but would see the odds tipped increasingly against them in 1942.

Long-term Threat: An Extended War of Attrition

The Americans might defer their major move west until after the fleets were reinforced by the flood of new construction due to begin arriving in late 1942. The Japanese had calculated that the Americans were building three to five tons of warships for every ton coming out of Japanese yards, and that American shipbuilding capacity would likely double during a war while the Japanese were already building at capacity. By 1944 they calculated the fleet ratio would be 10:3.
⁴⁰
While awaiting force superiority, the Americans would likely restrict themselves to raids against the more remote Japanese bases, avoiding a decisive fleet encounter.

The Americans might also raid the Japanese homeland, taking the northern route via Alaska. Attacks against Japan’s wood and paper cities were a frightening consideration, as was anything that directly threatened the life of the god-emperor.

Japanese Estimate of the Threat

As mentioned earlier, the Japanese had obtained information on the American Pacific strategy, but they did not have the Americans’ timetable. This stimulated a hearty debate within Japanese command circles. The scenario that eventually captured the support of the Naval General Staff was one in which the loss of the Philippines would so enrage the American people that the combined Atlantic and Pacific Fleets would thrust forward without waiting for reinforcement from new construction. There was a minority view that the Americans would wait, but that view was ignored in Japanese planning.
⁴¹

This was an American course of action that gave the Japanese a chance for victory. Japan had little chance for victory in a long war, and the Japanese knew it. They adopted a short war strategy which offered a chance to win, and built their force, trained their men and developed their tactics to support that strategy. They had no solution to the “long war” scenario—so they ignored it.

Eventually they became convinced by their own plan, and locked in by the inertia of their own bureaucracy with, as Agawa has noted, “a self-deluding formalism which assumed that the enemy would act according to predetermined conventions.”
⁴²
While confirmation bias and planning fallacy are an occupational disease of all human planners, national, historical, and military cultural factors made the problem especially prevalent among Japanese planners.

While the Japanese had the initiative in the first phase of their offensive, the Americans had control over the subsequent course of the war, and there was little the Japanese could do to influence that decision.

One look at possible Japanese thinking on the timing of the American advance can be found in the book,
The Three-Power Alliance and a United States-Japanese War
, published in Tokyo in October 1940. The author was Kinoaki Matsuo, a Japanese intelligence officer high in the Amur River Society, also called the “Black Dragon Society” after the Chinese name for the Amur River. The Society believed that the Japanese Empire should expand to the banks of the Amur. The society nurtured militaristic and aggressive aims.

Kinoaki stated that an American westward move would not happen without the joining of the Pacific and Atlantic Fleets. In his assessment, claimed to be based on information on United States naval maneuvers, it would take at least 60 days to join the two fleets, and another 60 to accumulate sufficient supplies to begin a westward offensive.

With a war beginning on 8 December, this would project the American advance to begin in early April 1942. By then, according to the Japanese warplans, both Singapore and the Philippines should have fallen, along with Java. Actual events unfolded with Singapore falling early (on 15 February), Java early (11 March), and the Philippines late (Bataan fell on 9 April). On 7 April 1942, when Kinoaki would have projected the beginning of the American thrust west,
Kido Butai
was attacking the British in the Indian Ocean, and the Japanese battle fleet was still in home waters. Kinoaki projected “a period of four months [when] the Japanese Fleet will be free to carry on its activities throughout the Pacific, and there will exist no strong opposing forces in the Pacific to interfere.”
⁴³

American Plans

American strategy in the 1920’s bounced back and forth between plans for a rapid thrust to the Philippines and for a more measured advance. The issue was resolved in December 1934, in a letter from the Chief of Naval Operations to the Commander in Chief, US Fleet. The CNO stated that, when the warplan called for the Pacific Fleet to be “established in the Western Pacific” and “at the earliest date,” these phrases should be used in conjunction with the phrase “in strength superior to that of ORANGE.” The fleet would not begin a trans-Pacific movement without superiority over the Japanese, and the expectation that it would remain superior even after losses en route.

The CNO went on to drive a final stake into the heart of any plan for an immediate movement to relieve the Philippines: “In other words, after a consideration of the ratio of strength between the BLUE [US] and ORANGE [Japanese] fleets, the so called ‘quick movement’ for the present has been discarded.”
⁴⁴

As the years progressed the schedule for a systematic advance was refined, and the schedule shortened. Fewer islands were to be assaulted and more bypassed. In plans developed before 1936, Truk was to be taken on day 75 after mobilization; later plans moved that up to day 59.

So, according to the 1930’s ORANGE warplans, there was something for the Japanese to fear in American plans for an attack into the flank of their advance, even in the contingency where the quick movement to the Philippines was abandoned.

Japanese Naval Strategy to Support the Southern Advance

The Japanese strategy envisioned a decisive fleet action between battlelines further and further away from Empire waters. In 1934 the battle was anticipated to occur near the Bonins and Marianas, 500 to 1200nm from Tokyo; in 1936, it was moved to west of the Marianas; in 1940 Yamamoto advanced the location eastward to the East Carolines and the Marshalls, 2500nm from Japan.
⁴⁵

This was a significant adjustment. Now, the Imperial Navy must capture
and hold
significant territorial conquests far from Japan. The outer defensive lines were no longer expendable, but had to become the reefs upon which the American Fleet was to be cast. The Interceptive Operations would have less depth in which to operate. The fleet would have to leave home waters and engage the Americans and British on the peripheries of their new empire.