Japanese Minisubs Key to Pearl History

Nova’s new season premier on PBS the night of 5 January, “Killer Subs in Pearl Harbor,” makes great TV watching for any World War II enthusiast or military historian. The episode is based in part on work, begun in the early 1990s, by three collaborating naval researchers: CAPT John Rodgaard, USN; scientist Peter Hsu; and Dr. Robert Neyland of the Naval History and Heritage Command. Accordingly, DOD held a conference call on 6 January between these experts and several military bloggers; I represented Defense Tech.

I learned quickly during the phone call that Nova only covered the team’s investigations through the year 2000, and the producers of the episode gave the team no chance to react to scripted conclusions. So it’s not surprising that there’s more to the story of Japanese minisub operations inside Pearl Harbor early on December 7, 1941. Rodgaard, Hsu, and Neyland have made a very convincing case that, contrary to most history books and the Nova episode itself, in fact two, not just one, of the five 45-ton, battery powered two-man Japanese minisubs – launched from their full-size mothership diesel subs outside Pearl Harbor between 0100 and 0300 local time that day – succeeded in penetrating the harbor defenses and then fired their two heavyweight Type-97 torpedoes. Using digitized photogrammetry, technical knowledge of the physics of underwater explosions, and an exacting timeline analysis, they demonstrated that one of these minis, the first to be launched that morning (which Nova called “Minisub #5”), was caught in a Japanese aerial photograph a moment after she’d fired one Type-97 at the battleship USS West Virginia and one at the battleship USS Oklahoma – and scored a direct hit on West Virginia. Mini 5 might have also hit Oklahoma. This information has significant implications both for historians, who figure out what actually happened in the past, and for historicists, who draw lessons from history to apply to today and the future.

The traditional take is that only one minisub got inside the harbor and fired its two torpedoes but neither scored a hit. This positions the Japanese minisub ops at Pearl as ineffectual, a mere afterthought to a decisively crushing carrier-borne aerial attack. The work of Rodgaard, Hsu, and Neyland supports a rather different conclusion. If two minis actually got near Battleship Row, and one of them got off two shots that helped destroy one or even two American battleships, then Pearl Harbor was an effectively executed combined arms assault by the Imperial Japanese Navy. But because the IJN was our sworn enemy during the world war that ensued, and because it lost unconditionally, it did not get to write the history books on the attack, at least in the West.

Why does this matter today? Because history provides raw data for historicists, especially in military matters. And what Pearl Harbor demonstrates to me, after the reinterpretation of events by Rodgaard, Hsu, and Neyland, is that undersea warfare power projection is an indispensable force multiplier for naval aviation during littoral combat. There are other important lessons here for today’s budget-strapped Pentagon planners and Members of Congress: Minisubs in modern form to be carried by fast and long-endurance SSNs and SSGNs – such as something that works well in place of the failed ASDS project, and various UUVs and sub-launched UAVs – deserve a priority in development and acquisition funding. Harbor security, which bears on both homeland defense and force protection worldwide, dare not shortchange the undersea dimension. Perhaps most generally and most importantly, ships and planes, no matter how capable and numerous, cannot do all the work that requires a robust, adequately resourced U.S. Submarine Force.

Part of the confusion over the years as to the role of Minisub #5 and the fate of the two courageous men aboard her comes from previously unresolved ambiguities concerning the track they took and their “final” resting place. I won’t reveal any spoilers here, but the research team’s answer ties in with another long-guarded secret of World War II operations at Pearl Harbor – a U.S. Navy secret only recently declassified!

Joe Buff

  • Robert Arnold

    Good point about sonar/stealth. Stealth shape/design would be important if sonar is active on the target ship. However I don’t remember any time when in port that sonar was turned on. Passive listening would perhaps work, but with all the “noise” in a harbor doubt that any bad guys would be picked up. I was only an ET, not a sonarman. Would like to hear what one of them thinks.

  • C. E. Hoffman, Jr.

    Did not the Brits use some form of mini-sub/manned torpedo in a failed effort to get at the German battleship in the Norwegian fjiord. Think I saw story on Military or History Channel back about 6-8 months ago. Also two IJN mini-subs have been found off Hawaii, as well as a couple of very technologically advanced ( ahead of anything USN had in the works or in the design loft) subs owned by our WWII enemies. We, the U.S. Navy, sunk them to avoid sharing gleaned tech with the Russians. Another recentg TV story on Cold War Russian boats said that a lot of their tech was ahead of ours. Their basic failures seem to have been Nuke power plants and “silencing”.

  • Just in regards to the ASDS mini-sub, can anyone really be sure the program has been canceled? Maybe it has only been publicly canceled with some press releases going out about a fire in the batteries and it’s failure to perform, but secretly it is in service? That would not seem to go against logic for a stealth underwater vehicle that should never be seen anyways.

  • chrisram

    Yes, the Brits attacked the the Tirpitz in port with X-subs I believe they were called. Only one sub made it there I believe and did damage the Tirpitz with it’s charges. Read the book Spec Ops by Bill McRaven (google him :) ) he has a good detailed, technical account of the raid.

  • Brian Mulholland

    There’s a bit of a mystery with the X-subs’ operation against Tirpitz, as well. One of the boats has been forever unaccounted for, and the memorial for those who died in the assault omits the names of the crewmen. However, British prisoners on Tirpitz’ deck (while awaiting the detonation of their Torpex charges) did observe a periscope, and the Germans fired on it. This may have been the missing boat – or maybe not.

  • chrisram

    Sounds like a good expedition to find that lost mini sub…..

  • chrisram

    Ben Rich also noted that when he proposed a 'stealth' submarine designed to deflect sonar waves the Navy responded “We don't design subs like that…” so he gave up.

    Mini subs are still a potent weapon and the Russians used them extensively during the Cold War. In fact there were rumors that the Navy found track marks (Supposedly the Russains had mini-subs that would crawl on the seabed) on the seafloor of one of our major seaports and they never figured out who put them there. The Swedes currently make some really nice mini-subs for special operations missions.

    I'd love to know if anyone has more insight into what the Russains did with mini-subs during the Cold War….

  • jsallison

    So, any wreckage found on the bottom at Pearl, yet?

  • stephen russell

    Proves Pearl was combined assult by:
    Air strikes
    & Minisub torpedo strikes.
    But air strikes did 90% damage alone.
    Very compelling.

    Imagine today mini subs penetrating New London CT sub base or Norfok NOB?
    Scary with Todays binary weapons, wow.

  • Joe Buff

    The 3 Navy researchers say all 5 Japanese minis at Pearl Harbor are now accounted for by locating and in some cases raising their remains. They do say that a 15′ section of the mini that they say hit West Virginia is not to be found with the other 3 big hull sections in its last resting place 3 miles outside the harbor in 1,200 feet of water. They think they know where it is (or was, as it might have been recovered or dredged up) but that would be a spoiler as to their very convincing theory about the wanderings of “Mini #5”.

  • DualityOfMan

    Believe it or not, the British attacked German ships in harbor using canoes and limpet mines during WWII.

    After the USS Cole attack (and perhaps experience with Somali pirates) the Navy is probably more wary about small craft, so I wouldn’t be surprised if subs were used in the future.

  • Todd

    “Part of the confusion over the years as to the role of Minisub #5 and the fate of the two courageous men aboard her…”

    It takes real guts to attack an unsuspecting ship during peacetime; /sarcasm about as much courage as it takes to stab a stranger in the back when they aren’t suspecting. This author has a warped view on courage.

  • JoeThePlumber

    Didn’t the people at pearl receive a warning from some intelligence agency before the attack and it was ignored or is that just conspiracy crap?

  • Wembley

    It’s worth mentioning that there is a small industry producing submersibles for drug smuggling these days – they have now spread from Colombia to Europe.

    Wouldn’t take much to fill one with explosives for a suicide attack.

  • Joe Buff

    Todd: It’s basic military doctrine in ANY military of ANY country to ALWAYS seek and exploit the element of surprise!!! PLUS the Gvt. of Japan did give USA what they considered honorable fair warning of war and the U.S. comms infrastructure proceeded to bury/delay/lose it until too late.

    JoeThePlumber: The best conspiracy theories are those like this one you mention, that MIGHT be true, are very sensational IF true, and can’t be proven to NOT be true!

  • Scott H.

    I seem to remember hearing (perhaps even seeing a photo) that a mini-sub was buried as part of the landfill expanding Subase Pearl during WW2. If so was it dug up, or is it still there? Or am I completely mistaken. While watching the TV show, I couldn’t help but wonder about that.

  • Matt

    IIRC one of the minisubs was abandoned in West Loch and only found when the Navy was doing salvage work after an accident in the area in 1944. It was hushed up because 1) the accident itself was classified and 2) it meant that the crew probably got away with the help of local collaborators. That sub was dumped with the rest of the debris outside Pearl.

    No idea about the new second sub though.

  • Joe Buff

    Scott H.: That sub you refer to was used as part of the rubble to create a breakwater at Pearl Harbor as naval/maritime operations there intensified due to the war starting. It is STILL THERE.

    Matt: The sub u refer to is the one that Nova calls Minisub #5, which the 3 Navy researchers identified as the first one launched at about 0100 local the day of the attack. They have strong evidence that the crew scuttled their minisub with an explosive self-destruct charge that all 5 of the minis are know to have had, the 2-man crew did this while submerged and their remains are believed to still be inside the pieces of the minisub that the two Pisces minisubs dived on.

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