Attack on Pearl Harbor (45 page)

This feat was accomplished by only a score of Americans with some recruited Italian prisoners of war. This ingenuity would be demonstrated by Americans repeatedly throughout the war under near-impossible conditions.

Compared to the resources Ellsberg had available at Massawa, a Pearl Harbor repair team would have had untouched civilian repair facilities at Honolulu and the Navy’s tenders afloat, considerably more manpower, and the support of local civilian contractors, all in a congenial climate. In addition, for special or esoteric needs, the mainland was a week’s transit away by steamer, a day by air. Obtaining replacement machines or materials would have been a matter of prioritizing, and with the mood in the Navy in the weeks after the Pearl Harbor attack, prioritization would not have been an obstacle. Obtaining replacement parts and tools for Pearl Harbor would likely have been viewed as a sacred duty.

There is no reason to expect that the Navy Yard could not have restored itself to full capacity faster than was accomplished at Massawa.

Destroying the Power Plant

Morison criticized that the Japanese “did not even attempt to hit the power plant.” This was another comment made without considering the means to effect the destruction or the consequences. Morison evidently made the statement without knowing what constituted the power generation capability at Pearl Harbor. There was not just one power plant, but several in different locations, along with a new 20,000 kW bombproof plant that had been under construction since October of 1941. It was not just a case of allocating one spare Japanese bomb and the lights would go out and everyone would go home.

If the Japanese wanted to take out the power plants they could have obtained the necessary intelligence, and could have been able to identify and target the plants from the air. However, their 250kg bombs were light for that kind of application. The USSBS found that knocking out generator halls was extremely difficult, and the damage often could be put to rights quickly.

The key to determining if the bombs were well employed would be the duration of the outage. It is likely that power would have been out for only a few days, perhaps hours. Historians never mention what would happen after the generators had been destroyed.

Every ship afloat had the capability to generate electric power for itself, often with sufficient overcapacity to allow for battle damage or to allow systems to be shut down for maintenance. This huge generation capacity could have been used to power the base.

In 1929 Tacoma, Washington was hit by a drought that cut the water supply to the city’s hydroelectric power plant. The carrier
Lexington
was directed to proceed to Tacoma to serve as a floating electric power station.
Lexington
arrived on 15 December, and two days later was tied into the grid and providing power at a cost of one cent per kilowatt-hour for 12 hours a day for the next 30 days.
Lexington
had a new turbo-electric drive using electricity to power her main propulsion motors, and had the capacity to generate 140,800 kW, so she was particularly suited to this task.
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Similarly, during the Korean War a destroyer escort provided power to Korean coastal towns cut off from their regular power sources.
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The battleship
Maryland
at Pearl Harbor had a turbo-electric main propulsion drive system similar to
Lexington
’s.
Maryland
’s plant was smaller, but the electrical demand from the naval base and shipyard would have been much smaller than that asked by the city of Tacoma, and there would be other ships available to augment the supply.
Maryland
had been hit by two AP bombs, but damage was minor, and her engineering plant was unaffected. She was moored inboard of the
Oklahoma
and pinned in her berth when that ship capsized, but freed on 10 December. She would have been ideal to provide this service. Alternatively, the tenders could have been used, as these ships were provided with sufficient electrical generation capability to power a nest of destroyers or submarines.

The destruction of the power plants supplying electricity to the Pearl Harbor base would have been a problem, but a temporary problem. It would not have had the strategic effects implied by Morison and Hart.

Conclusions: Attacking Pearl Harbor infrastructure

Admirals in the Pacific learned the great value of the Pearl Harbor Navy Yard throughout the early months of the war. It restored damaged battleships and two torpedoed cruisers and maintained the fast carrier task forces. In one celebrated case, without the Pearl Harbor Navy Yard,
Yorktown
would not have been ready for the Battle of Midway. Certainly admirals would shudder at the thought that the capability might have been taken away in the Japanese attack, as did Admiral Hart and Morison in print.

However, they did not consider what could have done to correct the problem. They did not consider the considerable alternative capacity in the repair ships afloat. Later in the war front line ships were well serviced by these repair ships and tenders far forward of Pearl Harbor. There is no reason why they would not have proven their worth earlier had the Pearl Harbor Navy Yard been incapacitated.

A Japanese third-wave attack simply would not have the firepower to inflict debilitating damage on the Navy Yard. Considering the available restorative capacity on the island, afloat and ashore, military and civilian, any damage could be put to rights in a short time.

Statements that a third wave attack against the shipyard would set the war in the Pacific back by a year are gross exaggerations. These targets were, indeed, as expressed by the Japanese Admiral Hara, “mere secondary objectives.”
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Attacking the Fuel Oil Storage Tanks

The other target mentioned prominently is the fuel farm. Admiral Kimmel considered that the oil storage would have been an even more lucrative target than the warships: “… if they had destroyed the oil… it would have forced the withdrawal of the fleet to the coast because there wasn’t any oil anywhere else out there to keep the fleet operating.”
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Goldstein, Dillon and Wenger claimed that not only would the destruction of the oil tanks have “crippled the entire Pacific Fleet,” but they extended the hyperbole by stating, “Their destruction would have rendered useless every military and naval installation in the islands.”
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Willmott, Tohmatsu and Johnson have stated that with the destruction of the oil “an intact Pacific Fleet, even if it suffered not as much as a single loss, would have been forced to withdraw to San Diego.”
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Admiral Nimitz is also on record as saying, “We had about 4.5 million barrels of oil out there and all of it was vulnerable to .50-caliber bullets. Had the Japanese destroyed the oil, it would have prolonged the war another two years.”
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Genda wrote after the war that the question of destroying the fuel tank farms only arose after the attack. “That was an instance of being given an inch and asking for a mile.”
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The objective was to destroy warships. Oil tanks did not enter into the original concept, and for good reason—when considered as a bomb hauling problem,
Kido Butai’s
aircraft simply could not transport sufficient ordnance to destroy everything it would have liked. The oil storage was never even on their agenda. Besides the well-known Japanese dismissal of logistics concerns, all the destruction of the oil storage would do from their viewpoint is to delay the American counterattack. If it was indeed a two-year delay as suggested by Admiral Nimitz, that would be about the time when the Pacific Fleet would have been greatly augmented by new construction and would have greatly outnumbered the Japanese fleet. A long war is not one the Japanese wanted to fight or thought they could win.

Given that, it remains to test if the Japanese had the capability to destroy the fuel tanks.

The Pearl Harbor fuel farms consisted of 54 major fuel tanks constructed on small hills and slopes in two complexes, one between the shipyard and Hickam Field, and the other above the submarine base. There were also aviation fuel storage areas on Ford Island with pipes and manifolds leading out to the Ford Island fueling pier berth F-4, where the oiler
Neosho
was moored at the beginning of the attack. The largest tanks had a capacity of over 10,000 tons of fuel; the total storage capacity of ships’ fuel was 563,000 tons. To place this in context, a full fuel load for the surface combatants in harbor the day of the attack (eight battleships, eight cruisers, and 30 destroyers) would have been about 61,000 tons.

Prewar, Pearl was serviced by three commercial tankers making a continuous shuttle from the California oil fields. They were delivering about 40–50,000 tons of fuel monthly, enough to meet the fleet’s training needs plus build up reserves to near capacity. The Pacific Fleet had a total of 11 tankers, of which four were fitted for underway replenishment.
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In addition to the surface tanks, a tremendous underground fuel storage project was begun in late December 1940. Called the Red Hill Underground Fuel Storage Facility, this secret installation eventually had 20 vaults with a total capacity of 5,400,000 barrels of fuel oil and 600,000 barrels of diesel for a total of 818,200 metric tons of fuel, over doubling the fuel storage at Pearl Harbor. The first of the vaults came on line on ten months after the attack, and the project was completed in September of 1943.

Destruction of Oil Storage by Machine Gun Fire

Nimitz believed that the fuel tanks could be set afire by .50-caliber machine gun fire. If this is true, failure to do so represented a significant lost opportunity for the Japanese.

The oil was stored in surface tanks with metal sides and a light conical roof to keep rain out. A flat top floats so there is no vapor space above the fuel, preventing explosive vapors from accumulating and keeping oxygen away from the fuel. The sides of the fuel tank were .75 of an inch to about 1.5 inches in thickness, tapered to increasing thickness near the bottom.

The Japanese aircraft did not carry .50-caliber machine guns. Their standard aircraft machine gun was the 7.7mm machine gun, a close relative of the British .303 machine gun.

Besides two 7.7mm machine guns, the A6M Zero carried two low-velocity 20mm cannon with 60 rounds per gun. The 20mm shell was designed to explode on contact with very light aircraft surfaces, thin aluminum or fabric, and so would not penetrate the tank sides. If hitting the roof, it would explode and hole the roof but likely would do little against the floating top. Fragments might penetrate the floating top, but would not have sufficient energy or any oxygen to ignite the fuel.

For fuel oil or diesel, a bullet would not ignite the fuel. If the bullet penetrates below the liquid level there is no air to support combustion. Even if there was oxygen, the flash point of the fuel is too high, and any bullets hitting a pool of fuel would not carry enough energy to raise any significant volume of fuel to temperatures where ignition could be sustained.
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Regarding penetration of the fuel tanks, Edward Rudnicki, a US Army ammunition expert, relates:

The idea the Japanese could have achieved a “cheap kill” by machine-gunning the fuel storage tanks is a myth.
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Destruction of the Oil Storage Tanks by Bombing

Assumptions that the Japanese attack the oil storage tanks with 280 250kg bombs, all the aircraft release their bombs, and all the bombs hit inside the area of the tank farms, and the wall of the tanks consisted of one inch thick mild rolled steel, a computer simulation was run that distributed the 280 bombs randomly within the target area. Over 1,000 trials, in 90% of the cases between 22 and 35 tanks were hit directly and another three tanks breeched by blast or bomb fragments. This represents 46% to 69% of the fuel tanks, or 259,000–389,000 metric tons of fuel.

Each of the fuel tanks was surrounded by a berm (called a “tank dike”) high enough to contain the entire capacity of the tank, plus extra volume to account for sloshing created by oil pouring rapidly out of a wall rupture. The radiant heat from a fire inside one tank dike can eventually ignite oil in neighboring tanks or dikes, but it would take at least an hour. The tank farms had a system of water piping and stray monitors to cool the surrounding areas to prevent the spread of the fire. Every tank would also have a built-in firefighting foam system. Since the Pearl Harbor tanks were relatively new, they likely had a central bunker that controlled the firefighting measures. Fuel from a burning tank or dike area could also simply be pumped from a burning tank into a safe tank. Transfer pumps were installed outside the diked area for this purpose.

There was a 10–15 knot breeze blowing at the time of the attack, so any smoke from upwind tank fires could conceal intact tanks, making the bombing problem more difficult.

The model suggests that about half the oil storage tanks would be destroyed. This is probably a high estimate. Setting fuel tanks on fire is a lot more difficult than it would seem. For example, the Haifa refinery and tank farm was shelled by Italian cruisers during World War II, without starting any fires. During the first Gulf War this refinery was the target of about a dozen Scud missiles. There were no direct hits, but one that exploded in a shopping mall across the street showered the refinery with hot missile parts, some of which hit and penetrated tank roofs. None started a fire.