All Attacks Aren’t the Same. That’s the Surprise.

So, a new memo has surfaced regarding US military intelligence prior to Pearl Harbor.

In the newly revealed 20-page memo from FDR’s declassified FBI file, the Office of Naval Intelligence on December 4 warned, “In anticipation of open conflict with this country, Japan is vigorously utilizing every available agency to secure military, naval and commercial information, paying particular attention to the West Coast, the Panama Canal and the Territory of Hawaii.”

That’s supposed to be a significant revelations? What, previous memos only warned about Japan’s keen interest in Minnesota? I hate to tell people who are all a twitter about this memo and other similar “revelations” but nobody in the American military or government was really surprised there was an attack on Pearl Harbor or any other major US pacific military asset. The entire Pacific was under a war warning and the entire US military was prepping for a possible Japanese attack somewhere. The US carriers were not caught at Pearl Harbor because they had been deployed to ferry aircraft to points in the western Pacific where an attack was anticipated, e.g., Wake Island.

Pearl Harbor wasn’t a surprise of intent, it was a surprise of capability.

No one in the US Navy thought the Japanese had the physical capability to strike Pearl Harbor with carrier aircraft. That was the surprise.

Yamamoto surprised the US Navy, and everyone else, because he was a “black swan”, i.e., a rare and unpredictable outlier.  

Yamamoto was arguably the greatest naval mind of the 20th Century. He saw possibilities that no one else did. In a culture that prized conformity and respect for the past, he was a maverick rule breaker. American planners did not and probably couldn’t have anticipated how radically and quickly Yamamoto would change Japanese doctrine, tactics and technology.

Yamamoto surprised the US Navy in two ways: Firstly, he completely inverted the controlling doctrine of the entire Japanese Navy. Secondly, he developed technology to enact that doctrine before anyone else thought to do so.

Japanese navel doctrine in the post-WW1 era was dictated by their belief that any future navel conflict would repeat the battle of Tsurigami, i.e., a US fleet would arrive in or near Japanese home waters, where a single decisive battle would take place in which one fleet or the either would be annihilated and the war would then come to a negotiated end. In such a conflict, long-range vessels would be unnecessary.  This doctrine arose in part because prior to the 1930s Japan would have been hard-pressed to get enough oil to fight a long-range conflict.

The home-water doctrine controlled absolutely everything in the Japanese Navy, from technology to training to indoctrination. Every ship was designed from the keel upward for an intense, short-ranged and short-duration conflict. Japanese ships usually had only half the fuel capacity of US or British vessels. All training focused on fighting that one climactic battle. Such a battle was portrayed as not only the only practical solution but the only moral one as well. This concept so dominated Japanese naval thinking that, after Yamamoto’s death, the Japanese navy instantly reverted to it. Making the conceptual leap to a radically different strategy was no trivial feat, and neither was convincing everyone else to go along. American naval planners were well aware of all this and they filed any possible long-range Japanese attacks by capital ships in the highly unlikely file.

After Yamamoto broke the pattern for the controlling doctrine of the Japanese navy, he next had to overcome the technological limitations. He had three major problems: (1) Fueling long-range operations, (2) developing air-dropped torpedoes that wouldn’t bottom out in the relatively shallow water of Pearl Harbor and (3) developing air-dropped bombs that could reliably penetrate the armor of capital ships.

As late as January 1941, none of that technology existed. American planners in December of 1941 assumed it still didn’t exist.

Yamamoto couldn’t just put a bunch of oilers (tankers) with the carrier fleet and set sail. The oilers were just large merchant vessels that couldn’t keep up with the fleet. The normal pattern was for tankers to stay around some island and for the warships to sally out and come back to tranquil waters to refuel. Nobody planned to bring tankers along on a sneak attack. Yamamoto solved the problem by constructing some oilers on some old cruiser keels which made an oiler that could reasonably pace a fleet.

The other problem was that refueling in even moderately heavy seas was tricky. Ships getting bounced around a tug at the wrong time could send flammable fuel everywhere. Yamamato solved that problem with a new kind of coupling system that could safely disengage.

This coupling technology gave the Japanese capital fleets unlimited striking range at good speed. Unknown to anyone outside the upper levels of the Japanese naval command, the Japanese carriers could strike West-East from Madagascar to the Panama canal and North-South from Alaska to Australia. The surprising series of naval air strikes that controlled the first few months of the war depended on the Japanese navy’s ability to refuel on the fly.

Yamamoto solved the other two problems with typical Japanese elegance and simplicity. Attaching wooden fins to the torpedoes allowed them to enter the water at a much shallower angle so they wouldn’t plow into the bottom of the harbor but would run true. Attaching fins to existing armor piercing cannon shells turned them into armor penetrating air delivered bombs.

American planners also took into consideration that even with the technical ability to strike plus the element of surprise, a carrier attack on Hawaii was very dangerous for the Japanese.

The Japanese had no more idea of the location of the US carriers than the US did about the location of the Japanese carriers. The Japanese fleet could have been counter ambushed and overwhelmed by the combined force of the US carriers, battleships and land-based planes from Hawaii. Admiral Nagumo failed to launch follow up attacks on the oil storage and dry docks of Pearl Harbor in part because of this realistic fear of a devastating counterattack.

American planners didn’t believe the Japanese would risk so many capital ships and aircraft in such a risky attack.

The combination of all these factors meant that even though Admiral Kimmel, General Short and others understood the theoretical dangers of a carrier attack on Pearl Harbor, they didn’t think it a likely enough scenario to take counter measures against, especially if that meant exposing Pearl Harbor to more likely forms of attack.

When they began actively preparing for war with Japan in early November 1941, they did not irresponsibly plan for an almost “impossible” carrier strike but instead responsibly planned for likely modes of attacks that the America navy thought the Japanese could carry out: Submarine attacks on ships, submarine shelling of the shore, submarine-landed commandos, aerial bombing from lumbering seaplanes and sabotage attacks by covert agents.

Kimmel seriously ramped up anti-submarine defenses around the harbor. Short put the coastal artillery on high alert. Both configured air defenses to repel a high-altitude attack from large seaplanes. Both guarded all land assets from commando or saboteur attacks. Most famously, both the Navy and the Army tightly clustered all their aircraft together on the airfields so they could be easily protected from a ground attack by light infantry or saboteurs.

Like competent baseball coaches, Kimmel and Short had covered all their bases. Unfortunately, the Japanese were playing football.

Most historical works conflate the surprise of the general public at Pearl Harbor with the surprise of the military. The Roosevelt administration worked tirelessly to downplay the risk of attack from Japan because FDR didn’t want attention distracted from Europe. Negotiations were still underway, and Americans of that era assumed that no one would attack during negotiations. The military, however, was actively preparing for war with Japan and was not particularly surprised that it broke out. They were only surprised by a radical change in Japanese doctrine and capabilities.

All the conspiracy theories about Pearl Harbor hinge on the idea that all the warnings about Japanese attacks should have made it obvious that a carrier strike on Pearl Harbor was imminent. Such theories ignore that the best intelligence estimates of the time said that Japan could not carry out such an attack, and even if they could would not as a matter of doctrine. Nothing in the bits and pieces of intelligence that in hindsight indicated a possible carrier attack on Pearl were interpreted as such, because a carrier attack was thought (as a practical matter) operationally impossible.

The specter of technological surprise has haunted US planners ever since Pearl Harbor. The US military did learn to never underestimate the technical ability of an enemy to strike. Some would argue the US has systematically over estimated such abilities.

We learned a lot from Pearl Harbor but we really didn’t learn not to attempt to read the minds of people from other cultures and ideologies We haven’t learned to plan for the appearance of exceptional individuals changing the rule of the game.

Most importantly, we haven’t learned to plan for things we can’t possibly plan for or to admit that such scenarios even exist. Instead, we assume that all eventualities can be and should be planned for.

No doubt future historians will write “books” about how everything we will blunder into was in retrospect so obvious that the only reasonable explanation was some grand incompetence or conspiracy. In the end, we just really don’t understand most of what is going on and never did or will. Life is about surprises good and bad.

25 thoughts on “All Attacks Aren’t the Same. That’s the Surprise.”

  1. Yes, hindsight is always 20/20.

    An excellent book for an overview of this whole topic is John Toland’s “The Rising Sun”.

  2. I think the British added fins to their torpedoes at Taranto. Yamamato very carefully copied the British attack plan. Short and Kimmel were the recipients of Roosevelt’s successful blame shifting. He did include a war warning but adroitly avoided the blame for lack of imagination.

    What is still a mystery is MacArthur’s funk on December 8 when he had plenty of warning from Pearl Harbor. It is probably similar to that of Stalin when Hitler attacked.

  3. MacArthur’s funk I attribute to peacetime habits in the staff (i.e., Richard Sutherland). My follow-on research question would be how the military forces (or even just the USAFFE headquarters staff) on the Philippines had prepared for the onset of war. They acted under-prepared; were they?

  4. Japanese navel doctrine in the post-WW1 era was dictated by their belief that any future navel conflict would repeat the battle of Tsurigami…

    We shouldn’t be surprised at the aggressive Japanese tactics, as they have a long and storied tradition of excellence in navel conflict.

    And by the way, I notice you have a few interesting typos in this article.

    That seems to be true of many of your best postings, Shannon. Do you have a hypothesis as to why this is so? Is it because those articles are the ones you are most excited about, or is it because you dash them out on a smart phone when an idea strikes you.

  5. Michael Kennedy,

    I think the British added fins to their torpedoes at Taranto.

    Actually, they used a rather complex system of a wire on a drum attached to the plane to pull the nose of the torpedo up as it fell.

    I really think disdain for the Italians drove a lot of Americans to ignore the lessons of Taranto. Italian disorganization contributed mightily to the British success. Fairy swordfish could have never lumbered into Pearl Harbor and dropped their torpedoes in the slow, shallow and accurate way they did at Taranto. They would have been massacred. Taranto was looked upon more as fluke caused by British excellence combined with Italian ineptitude than as a for bringer of future warfare.

    Racism against the Japanese, despite many warnings by fellow Americans like Chernault, drove many to assume that the Japanese pilots, planes and ordinance couldn’t be better than the British. It seemed unlikely they could do the same even if they got to Pearl Harbor.

  6. What is still a mystery is MacArthur’s funk on December 8 when he had plenty of warning from Pearl Harbor.

    MacArthur would get massively surprised again in Korea. I think he was an unbalanced general who simply ignored defensive preparations. On Dec 8th, he was psychologically preparing to hit back and didn’t think to prepare for a Japanese attack.

    Also, like everyone else, American planners in the Philippines did not understand that the Japanese had created a long range striking force (including long range land based bombers) and the doctrinal will to use them. The air planing for the Philippines seemed to have assumed they were out of range and safe from surprise attack.

  7. The air planing for the Philippines seemed to have assumed they were out of range and safe from surprise attack.

    There was actually an American force on the runways waiting for orders to Formosa. The surprise and consternation seems to have been mostly at the top.

  8. ‘Fairy swordfish could have never lumbered into Pearl Harbor and dropped their torpedoes in the slow, shallow and accurate way they did at Taranto.’

    Once in the harbor, with few defending fighters able to leave the ground, which plane type was used wouldn’t matter much. I doubt attack speed would be much different between the Swordfish and the Kate.

  9. It is one of the ironies of WW II that Kimmel & Short were ruined for Pearl Harbor while MacArthur held onto his command not only after Dec 8th (I don’t care how sure you were that your bases were safe from attack – after learning of Pearl Harbor you certainly should have started testing your assumptions), but also after the disaster of the rest of the Phillipine campaign.

    Short was unlikely to have a significant command in any event, so he was an obvious scapegoat under the circumstances. Kimmel, who was by all accounts an excellent commander, was probably dragged down by the Army’s determination not to take the bulk of the blame. Fortunately for the US, Kimmel’s disgrace allowed Nimitz to take command in the Pacific.

    Personally, as regards to FDR and his role in the events that brought the US into the war, I think the case is strongest that he set out to provoke incidents in both theaters (Ruben James anyone?) with the goal of getting the US into the war in Europe. Japan had been killing Chinese for almost a decade without provoking a serious US diplomatic response. Only after the war started in Europe and Japan aligned itself with Germany did FDR start the escallating embargos that convinced the Japanese that war was necessary. I agree that Pearl Harbor wasn’t what he was shooting for, but war certainly was. A direct Japanese attack on any US or Phillipine territory would have been enough for that.

  10. Since the Philippines was across the date line from Hawaii – what was the interval – in hours – between attacks on Hawaii and Clark Field?

    According to the Stinnet book we did know a Japanese fleet was out “there” – it was big – but we didn’t know where I didn’t until a year or so ago realize there were 2 Japanese codes we broke – one for the military and one for the diplomatic Service. According to Stinnet we were decrypting the military codes months before Pearl.

    All from a little nondescript building at Pearl where the regular Navy personnel complained of strange people with B.O.

    In Kimmel’s and Short’s defense we had been getting warnings since the 1920s – you cannot stay on a permanent state of high readiness. Of course they were becoming more frequent by 1941.

    I think they were both scapegoats.

    Of course all the knowledge Shannon says we could have used was used – just a few months later – at Midway where our gamble was just as audacious as the Japanese at Pearl – and rewarded almost as handsomely.

    Timely post Shannon as tomorrow is Dec 7th.

  11. Wade McCluskey saved the day at Midway. He is forgotten and should be a hero of that war. He turned the right way and found the Japanese fleet. Had he turned the other way, nobody would know of Midway except, perhaps as a lost opportunity. It is a freak of fate that one man had such influence on history. The Hornet dive bombers did turn the wrong way and missed the battle.

  12. I had forgotten about McCluskey. If I am not mistaken a Japanese carrier captain also made a crucial mistake having all his planes changed from bombs to torpedoes (or vice versa) and all his fueled planes were caught on the deck when the attack came.

    It came down to who would find whom first.

    Then there were the defective bomb release mechanisms and the flyers who went in unarmed just to draw fire away from those who were still armed. (I am “assuming” the movie was accurate in that regard?)

    The guy who had the most interesting seat was Ensign Gay


  13. …and I was thinking of what Lex said about Adm King….and how this factoid ties in…

    “In the time it took Japan to build three carriers, the U.S. Navy commissioned more than two dozen fleet and light fleet carriers, and numerous escort carriers.[121] By 1942, the United States was already three years into a shipbuilding program, mandated by the Second Vinson Act, intended to make the navy larger than Japan’s.[122] The greater part of USN aviators survived the Battle of Midway and subsequent battles of 1942, and combined with growing pilot training programs, the US was able to develop a large number of skilled pilots to complement its material advantages in ships and planes.

  14. I wonder what would have happened if Yamamoto had decided to go for the big prize and attacked the Panama Canal instead of Pearl Harbor. It was a lot further, but if he had the underway replenishment down pat that wouldn’t have mattered. If they had destroyed the locks they could have put the Canal out of commission for 2-3 years, and that would have hampered US operations in the Pacific enormously. As it was all they really got at Pearl was a number of old, slow, 14-in gun battleships that were already obsolete for main battle fleet use. And with the Pacific Fleet intact the USN might have been tempted to execute Plan Rainbow and sortie the fleet to the relief of the Philippines. If the Japanese could have drawn the fleet within range of Japanese land aviation for the battle it would have been very questionable for the US.

  15. Great post, Shannon! I wonder what is the source for Yamamoto’s switch to fast oilers and
    the armor piercing bombs? the shallow running Japanese torpedos have been known for a while,
    but this is the first I have read about the oilers and the armor-piercing bombs.

  16. As I understood it, Kimmel had gotten his job because Richardson (the previous CINCPAC) kicked up a fuss about moving the Pacific Fleet from San Diego to Pearl, precisely because of concerns about an attack on the fleet. And then Washington declined to share intelligence with Kimmel, and made him a scape-goat when his fleet went boom.

    It seems clear to me that Roosevelt wanted something like Pearl Harbor, although the ‘new’ information doesn’t really tell us anything new. That said, I don’t really think the US policymakers took Japan all that seriously as a threat before the war; Roosevelt rather felt it was a convenient excuse to get the war he did want.

    A lot of people at the time really couldn’t grasp the Japanese mindset, though. For example, they couldn’t believe the performance of the Zero until they’d captured one; after all, with the engines the Japanese had you couldn’t build a plane with its armament, range, and performance while still adequately protecting the thing. Turns out the experts were pretty much right on that; the Japanese just defined down “adequately protected,” ditched most of the armor and built it anyway.

  17. John Cunningham: This is from John Toland’s book “The Rising Sun”, in the chapter entitled “Operation Z”.

    “Kusaka didn’t believe this second assault could succeed without an accurate bombsight – the Japanese knew of America’s Norden bombsight but had been unable to acquire the plans – or a bomb capable of piercing a battleship’s thick armor without detonating. The answer to the first problem was constant practice with the erratic Type 97 bombsight, a copy of a German model; for the second, Genda, Fuchida and the engineers finally hit upon a simple solution: reconstruct battleship shells into bombs, with their outer faces so reinforced that they would not explode on impact”.

  18. John Cunnigham,

    Great post, Shannon! I wonder what is the source for Yamamoto’s switch to fast oilers and
    the armor piercing bombs?

    The armor piercing bombs is multi source, probably the Toland book mentioned about. It might mention the tankers as well but I think I first read a reference to in a book called, “Why the Allies Won” which looked a logistical issues of WWII. I can try to dig it out if you need more.

  19. Superb post Shannon!

    The Japanese Empire only had one hope, to make an attack so politically calamitous for FDR that they could negotiate a deal. It would not have mattered if they had seized Hawaii and destroyed the canal. Depression-peacetime America with idle capacity made 100 million tons of finished steel a year and was self-sufficient in all war materials except rubber and exotic metals like wolframite and chromium. Imperial Japan made 7 milion tons of steel and had no oil while having most of their army bogged down in China.

    The Japanese would have been better off if they had attacked the USSR alongside Hitler

  20. One comment stated that Gen MacArthur was massively surprised in Korea. I assume the reference is to the Chinese crossing the Yalu into N. Korea. Our intel simply did not know this was to take place …I was on a troop ship heading for Korea when that invasion took place and, later, with a patched together intel op the quality of information
    got significantly better …recall that NSA was still young at the time, having merged with the Army Security Agency, whose job it was to monitor electronic commnunications.

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