Alan D. Zimm
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In one seminar after a joint Army-Navy wargame, an officer raised the possibility that the Americans might do something other than make a move to relieve the Philippines—for example, they might immediately launch an attack against the Japanese mainland. Surely different eventualities should also be studied? A Naval General Staff officer supervising the maneuvers replied:
The campaign against the Philippines has already been decided on as operational policy by the imperial navy, and as such is under study in collaboration with the army. It is highly regrettable that one should hear arguments rejecting it. We must not forget that to coordinate ideas on strategy is one of the aims of these exercises.48
The War in Europe’s Impact on Pacific Fleet Strategy
On the American side, the ORANGE warplan was superseded by the RAINBOW series, which looked to a world war. It opens with a statement of overwhelming significance to the Pacific Fleet:
Since Germany is the predominant member of the Axis powers, the Atlantic and European war is considered the decisive theater. The principal United States military effort will be exerted in that theater and operations of United States forces in other theaters will be conducted in such a manner as to facilitate that effort.
As a secondary effort, the Pacific Fleet was to act “offensively in the manner best calculated to weaken Japanese economic power, and to support the defense of the Malay Barrier.” A “vigorous offensive,” with “bold aggressive action,” was desired.49 These clarion calls were stirring in principle, but in practice would be difficult. More of the Pacific Fleet was siphoned off for Atlantic duty, scheduled arrivals of amphibious shipping and troops were delayed or redirected, merchant shipping became scarce, and the Pacific Fleet so starved for oilers that its radius of action was curtailed. With fewer ships, fewer Marines, and fewer auxiliaries, the idea of taking Truk by day 59 or day 75 or even day 180 was clearly impossible. RAINBOW forced a “long war” strategy on the Pacific Fleet.
Regardless, Admiral Kimmel, the Commander in Chief of the Pacific Fleet, planned for offensive action with carriers and battleships operating against the Marshalls, commencing only a few days after the beginning of hostilities. In addition to raiding, Kimmel had a rather fantastical plan to lure the Japanese fleet into battle by offering his aircraft carriers as bait.
Kimmel knew the Japanese would have to come to him, as he could not go to them. It would be hard for his force to work further to the west than the Mandates. The Pacific Fleet had four oilers equipped for underway replenishment of warships, but needed 25 for extended operations.50 With the war in Europe’s insatiable appetite for shipping, and the German U-boat offensive sinking dozens of ships every month—while the American public was still addicted to its Sunday afternoon drives—shipping, particularly oilers, would be hard to snatch away.
Logistics, Forward Bases and “Unsinkable Aircraft Carriers”
If the Japanese were not totally blind to logistics, they were at least vision-impaired. They operated their forces with the barest minimum logistics support, often beginning operations with insufficient supplies to carry them through to completion. The construction of warships was always a higher priority than auxiliaries. Logistics concerns were secondary when constructing their outer lines of defense in the Pacific.
Some of the Japanese neglect stemmed from treaty restrictions. As a reward for participating in World War I, the Japanese were given the Mandate Islands in the Pacific under the League of Nations. As a price for accepting the 10:6 ratio in the Washington Naval Treaty, the Japanese insisted on a ban on fortifications in Pacific areas, denying Western powers forward support bases to operate against Japan (Article XIX). Eliminating fortifications matched both their needs and their inclinations, as it prevented a “base development race” in the Pacific that the Japanese wanted to avoid financially as well as strategically. Even after the Japanese abrogated their participation in the naval treaties and withdrew from the League of Nations, their concept of operations, where they expected to lose their outlying possessions during an attrition phase of the American advance, marked these possessions as expendable. Base development would be limited to the bare necessities to support attrition operations against the American advance.
For example, Truk, the Fourth Fleet’s base from November 1939, was the strongest Japanese naval base in the Pacific. However, the Japanese “Gibraltar of the Pacific” had minimal shore repair facilities. Fuel storage was totally inadequate, eventually consisting of one 10,000-ton capacity underground tank and two above-ground 50 meter diameter by 20 meter high (250,000 bbl, 33,600 ton) steel tanks, a total storage capacity of 77,200 tons. The remains of these tanks can be seen today, though it is not known exactly when they were constructed.
To place this capacity in context, to fill one battleship would take about 5,000 tons of fuel, a heavy cruiser about 2,500 tons. If just the Japanese battleships and heavy cruisers of the Combined Fleet arrived, the fuel storage at Truk could not give them all a single ship fill. The 77,200 tons of fuel storage can be compared to the Americans’ forward base in the Pacific, Pearl Harbor, with storage for 563,000 metric tons of fuel with additional capacity under construction.
During the war the IJN anchored tankers in Truk Lagoon as fuel storage “station ships.” Instead of moving fuel the tankers acted as floating storage tanks, a burden on the limited Japanese tanker fleet.51 Insufficient fuel transportation would be one of the three greatest causes of the defeat of the Japanese (the others being the inadequate wartime replacement of pilots, and the starvation of industry by the destruction of Japan’s maritime transport).
The attitude of the Japanese to logistics is exemplified by an anecdote from one of their chart exercises. A unit was being advanced to contact with the enemy. To save fuel for high-speed operations in the vicinity of the opposing fleet, a slow speed of advance was initially dictated. This was criticized. The advance lacked “alacrity.” Too much worry over fuel made “proper” maneuvers impossible. When forces were calculated as out of fuel, they were simply assumed to have been refueled at sea, and the swift advance continued.52
Logistics considerations were similarly ignored when making strategy. For example, in early January 1942 the Naval General Staff performed a study on invading, capturing, and sustaining a Japanese garrison in the Hawaiian Islands. Three million tons of cargo would be required to feed the islands’ population over a year’s time, and 30 ships per month to transport military equipment, a total of 60 shipments a month. A nine-knot freighter would take 36 days to make the round trip in transit time alone, not counting loading and unloading time and ship’s maintenance and time spent awaiting escorts. The study concluded that Japan’s overstressed merchant marine could not meet the requirement. This study did not consider that the food might not even be available from Japan, as food shortages were already a serious topic of conversation in homes throughout the Empire.53 Obtaining food supplies directly from Indochina might double the shipping requirement.
In spite of this, members of the Japanese high command continued to advocate an invasion of Hawaii. One month after the Doolittle raid, the army joined in the decision to seize Hawaii.54 Only the Battle of Midway put an end to their Hawaiian ambitions.
Mirror Imaging
Just as the Japanese tended to gloss over logistics concerns when making their own strategies, they tended to ignore logistics limitations confronting the enemy. The attitude of “mirror imaging” deserves mentioning. In mirror imaging, a side projects onto the enemy its own attitudes and beliefs and capabilities. In some ways this is a conservative viewpoint. Each navy tended to believe its intellectual foundation and abilities were superior to that of the enemy. If your own abilities are projected onto the enemy in a map maneuver or force calculation, and the enemy allowed to use your own concepts of operations, then you are attributing to them the “best” capabilities. If you can defeat them under those assumptions, you ought to be able to defeat them even with more assurance under actual conditions—presu
ming that the enemy was really inferior in that area as supposed, and they do what you expect them to do.
Both the Americans and the Japanese tended to mirror image. For example, on the American side, intelligence was rare on the performance and characteristics of Japanese warships and weapons. With no information on the performance of the Japanese 41cm (16.14-inch) guns mounted on the Nagato class battleships, the Americans simply assumed that it performed as well as the equivalent US 16-inch gun. When US Navy intelligence got their first sniffs of the construction of the Yamato-class battleships, they projected they would be quite similar to the Americans’ Iowa-class, with 16-inch guns in triple mounts and just about the same tonnage and speed. A year after the Japanese introduced the 24-inch Type 93 “Long Lance” torpedo, Navy intelligence dismissed the idea that the Japanese could have developed an oxygen torpedo, because the Navy’s Bureau of Ordinance declared such a weapon to be impossible. “Neither the British nor the Americans had yet mastered oxygen technology, so it was inconceivable that the Japanese had done so.”55
Often this was done consciously. For example, a secret publication from 1944 dealing with the damage resistance characteristics of ships stated:
Since practically no information is available on the defensive characteristics of Japanese ships, the best assumption that can be made at present is to assume that the Japanese ships have characteristics approximately equal to those of corresponding ships in the U.S. Navy… it is believed that a large proportion of the Japanese fleet is made up of older ships with power of survival roughly equivalent to that of corresponding older ships in the U.S. Navy.56
In fact, this assumption was not very good. Japanese warships were optimized for speed and offensive power, and had considerably less resistance to damage and less damage control capability than comparable US Navy ships.57 The Japanese mirror imaged when they assumed that American land-based air would be primarily directed against ships (as was the IJN’s land-based air), that American submarines would be primarily used against warships in the same doctrine as Japanese submarines, and that the American move to the western Pacific would contain the same slapdash, “damn the logistics, full speed ahead!” neglect as the Japanese displayed in their own strategies.
For the Japanese, this also extended to a lack of flexibility in their assumptions, a “self-deluding formalism which assumed that the enemy would act according to predetermined conventions.”58 Anyone questioning orthodoxy was slapped down.
Development of Forward Bases and Mobile Repair Capability
Because of a lack of materials and the ships to transport them, most development of forward bases used local materials and hand labor by the garrison. The paucity of shipping meant that many islands were chronically short of food, fuel, and stores; materials for fortifying a base were sent in bulk only when a particular location was considered “next in line” for Allied attack.
Minimal also, when measured against American standards, was Japan’s maritime development of Truk. Greater additional fuel storage and other facilities at Truk were certainly warranted. Some were built as the war progressed. Rather than providing piers, the fleet anchored in the lagoon. Supplies were delivered using small lighters. Having no piers or shore services—including steam, electricity, and potable water—meant the ships were constantly providing their own services, placing more wear and tear on their engineering plants, and having less availability for maintenance, less rest for the engineers, and a constant drain on the ships’ fuel. Shore services could have been run on coal, which the Japanese had in abundance. Plus, coal did not require large (and vulnerable) storage tanks and pumps and piping. At Truk, the Japanese simply dumped coal in a heap near to where it was needed.
Damaged ships could get some help from a few tenders or an itinerant repair ship, but the Japanese did not have forward-deployed mobile dry docks. Ships with underwater damage had to go either to Singapore, back to the home islands, or (for some smaller ships) to captured American facilities in the Philippines. Ships damaged and not seaworthy enough to transit to one of these facilities were essentially lost for the duration—as the war progressed, scores of damaged warships and particularly merchantmen were anchored on whatever odd harbor they could reach, and there abandoned.
The Japanese inventory of forward-deployable repair ships was miniscule. Akashi was the only purpose-built repair ship in the fleet; she was joined by Asahi, converted in 1938 from a pre-dreadnought battleship, and Yamabiko Maru, converted from a 7,000-ton passenger steamer in 1941. Two other small ships added some repair capability. Matsue Maru, a 5,644-ton cargo ship, was converted into a “Specially Installed Construction Warship” in April of 1941, and Urakami Maru, a 4,317-ton cargo ship, was converted into a “Salvage and Repair Ship” in January of 1942.59 These ships helped with maintenance and repair, but mostly they tried to make damaged ships sufficiently seaworthy to transit to a shoreside repair facility.
Other forward bases, the “unsinkable aircraft carriers” and “unsinkable submarine tenders,” were similarly neglected prior to 1937. When given a choice between spending money on new warships or on forward bases, the Japanese placed a priority on warships. And, according to the treaties awarding control of the Mandate Islands to Japan, the islands were not to be fortified.
Even today the Japanese like to believe that the islands were unfortified. Agawa relates a story from 1937 where the American naval attaché in Tokyo sought permission to visit the Mandates but was refused, “not that [the IJN] did not want him to see installations being built in that area, but that it was afraid he might find out that there were no decent military installations at all; it wanted to leave him with the impression that some did, in fact, exist.”60
However, this is disingenuous.
The islands in question were Class “C” Mandated Islands under the League of Nations, where the occupying nation administered the territory under its own laws, in this case as if the islands were part of Japan. They were not allowed to fortify the islands.
However, Japan withdrew from the League of Nations without returning the Mandates, and from 1937 they ignored restrictions on military development. Japan publicly insisted that it was not fortifying the islands; however, there was brisk development of ports and airfields and associated facilities for “economic development,” facilities that certainly would have dual-use military applications in wartime. The exact extent of the development was difficult for outsiders to determine, since Japan discouraged travel to the islands, controlled entry rigorously, and guarded the sea approaches. Shipwrecked mariners were confined, closely guarded, and removed from the islands promptly. Westerners referred to them as “Japan’s Islands of Mystery.”
By June 1941, $28 million (equivalent to nearly $1 billion in 2009 dollars) had been expended throughout the Mandates, including $7 million ($250 million) on Saipan, Tinian, and Pagan in the Marianas. Facilities included airfields on Kwajalein in the Marshall Islands, Saipan in the Marianas, and Truk, along with port facilities such as piers, warehouses, and workshops. In 1939–40 seaplane tenders Chitose, Kamoi, and Kinugasa Maru carried construction crews and technicians to build seaplane ramps at Truk, Palau, Kwajalein, and Saipan. The tenders made several round trips to Japan to obtain additional construction supplies.
The Japanese insisted that these facilities were built for economic development. However, over the years, it was apparent that the authority controlling the location and design of coastal and island facilities shifted from civilians to the Japanese Navy. When examining the plans for such facilities as Aslito Airfield on Saipan (begun in 1934), it was found that most buildings were constructed to be bombproof and designed for easy conversion into military use, such as a facility for the assembly of aerial torpedoes. Many of these airfields, such as those on Saipan and Kwajalein, were used to launch air strikes in the opening hours of the war. The seaplane ramps facilitated operations of long-range Japanese reconnaissance flying boats such as the H8K Mavis.
While the Japanes
e limited development of fleet support bases, they did develop outlying islands to support offensive operations by bombers, reconnaissance planes, and submarines. In the context of the original Japanese strategy, overseas bases designed for the long-term forward sustainment and repair of the fleet would not be necessary. The war was supposed to be short, so it would be unlikely that seriously damaged warships could be repaired in time to participate in further actions. The decisive battle would be close to the Empire, so forward bases might be expected to fall to the enemy in the course of the Fabian retreat or be bypassed and isolated, so even the offensive base development was limited to the bare necessities. All that would be needed in the way of forward bases would be limited facilities to service reconnaissance seaplanes, medium bombers, and submarines. For the fleet, all that would be needed would be facilities in home waters.
This strategy was exploded when it was decided to invade and hold the forward resource areas in the Greater East Asia Co-Prosperity Sphere. Now, the Navy was being asked to take and hold islands thousands of miles from Japan. Under these new circumstances, the other primary reason for minimizing development of remote bases came to the fore: lack of resources, coupled with a lack of priority.
The Japanese economy was under a severe strain. They had been at war with China since 1931. Japan was smaller than the United States, in land, population, and resources. Remarkably, Japan had nearly matched US military expenditures during the interwar years with an economy no more than 15% as large. However, there was little remaining slack in the economy, and few civilian production facilities left to convert to war production. The competition for resources with the Army meant that the Navy could not have everything it needed. “The IJN was hard into the stops on the nation’s total steel supply,” critical for ammunition and ship production.61
Under those circumstances, and in accordance with their national psychology, the Japanese chose to invest in the means to attack rather than the means to defend and sustain. This makes sense on a superficial level: if the forces created to empower the attack did not succeed, any infrastructure of stores or facilities on remote bases could not reverse a setback in the Final Decisive Battle.