Hi Local Yokel,
Happy to discuss the issue. I remember the exchange on j-aircraft well. The exchange at times got rather acrimonious - from that I should have learned to maintain a more even keel in such discussions. After the exchange with Nikademus I will remember to deal with such discussions in a more circumspect manner. What I found frustrating was the devotion to some beliefs that I found to be totally unsupportable, and the elastic standards of evidence. Some of the folks were absolutely convinced that the 5th midget penetrated the harbor and torpedoed Oklahoma and/or Arizona, and they were looking to prove that. Looking to prove something is very different from an investigation looking to find out what really happened - you tend to accept circumstantial evidence, and reject or not even consider arguments and evidence against the proposition.
The difficulty is that none of the cases proposed in the investigation could muster evidence that resulted in an answer that would meet courtroom standards, i.e., "beyond a reasonable doubt." Most of the testimony - clues - are circumstantial. This is why I took the approach that I did in the book, to outline a model of most the events that would have to occur in order for someone to believe that the 5th midget was actually in that photograph - it was a vehicle to promote discussion. A reader could then plug in their own levels of belief. It was a good approach to address most of the ssues in the debate.
I'll summarize what I think the evidence (such as it is) reveals as the most likely explanation. As you mention in your post, 8 of the 10 torpedoes have been accounted for. I believe that one or two were fired at the St Louis as she departed the harbor. The captain and XO saw the torpedo wake(s), made a bell change to try to evade, and observed the detonation of one of the torpedoes when it hit the reef at the edge of the channel. Besides the testimony of the CO and XO, and the log, there are three others who observed the wake and the torpedo detonation and have left testimony - an officer in the forward superstructure, an officer aft, and another enlisted man. All of them mentioned observing the wake and that the ship was drenched by water from the plume of the explosion.
I believe also that this event explains the radio message that the Japanese received reporting "success" - a torpedo detonating so close to the ship would have been seen as a direct hit from a periscope only a foot or so above the water.
Arguments that the plume of water was actually the explosion of a descending AA projectile I do not believe are valid, for several reasons: first, the fact that the torpedo wakes were sighted; second, the huge difference between a torpedo detonation plume and that of a 5" AA projectile (600 foot plume v. 60 foot); third, the time (1004), was after the withdrawal of the second wave of the attack, and so there was no reason for AA guns to be firing.
The original reports said that two wakes were sighted. At one point the supposition was that both torpedoes detonated on the reef. However, the reports also stated that there was only one explosion. The MRI (minimum release interval, i.e., time between launching two torpedoes) on a Japanese midget sub was on the order of 30 seconds, so the chances that a second torpedo's explosion would be mixed in with the first is unlikely, since a torpedo explosion plume lasts about 14 seconds (up and down). So, either the second torpedo just missed and motored off into the Pacific, or it was fired at another ship at another time. Thus, I introduced Helm's report as a possible place where the second torpedo was expended. In the Helm's report, the torpedo was allegedly sighted by crewmembers as having passed under the stern of the DD. The midget submarine's torpedoes were likely set to a depth of 22-24 feet (appropriate to attacking battleships), so this makes sense, plus the signature of a torpedo passing that close (!) ought to be unmistakable and clearly different from that of, say, a dolphin or other marine mammal (often reported as torpedoes). Helm's report was to me the most creditable of a large number of reports of torpedo attacks against US ships that day.
Any report that is not accompanied by a physical manifestation (like an associated explosion) has to be taken as problematic in that day's atmosphere - there were reports of Japanese paratroops landing on the island, Japanese transports off the beaches, and Japanese aircraft carriers rounding the point; some US DD ship COs off the harbor thought that the explosion of descending AA rounds were actually torpedoes at the end of their runs, and thought that the waters around the channel were infested with submarines. People were seeing a lot of things that just were not there. I've done some work in cognitive science - if you are interested, I can give some explanation of the mental sources of the phenomenon.
I was in the Navy during the Falklands War and I remember reading about all the troubles that they had with false reports of Argentinian submarines, to the extent that they were running out of AS torpedoes, having fired so many at false targets. Human nature does not change.
The bottom line to me is that at least one torpedo was definitely expended against St. Louis, establishing that the midget was outside the harbor. Where the other torpedo was fired is somewhat immaterial - it could just as well have been fired but never seen by an US observer.
You asked about the possibility that the torpedoes could have been fired by a fleet boat, and why I did not discuss the argument regarding whether the fleet boat would have had enough water to operate. I did not discuss it for a few reasons. First, I had not looked at the charts myself. Second, I think it was Will O'Neil who had originally made the point with some chart work, but, later, another person did some work that came up with a different conclusion. While I would hold a bias towards Will's work (he is a Captain, USN (ret), and I know him by reputation as an outstanding analyst, one well familiar with naval charts and submarine operations), I was at such a point in the production of the book that I did not have the time to examine both arguments in detail. I'd bet my paycheck on Will, but I would not publish something like that without personal verification.
Third, the reason that I wasn't compelled to examine the issue in detail was because I was 99% confident that a fleet boat did not expend any torpedoes that day. Lots of reasons. First is that none of the fleet boats reported such an attack. The Japanese navy had a shortage of submarine torpedoes. The Japanese submarines were also under positive control of their admiral similar to the way that Doenitz controlled the German submarine fleet, so there were a lot of messages flying back and forth. Japanese sub captains were under orders to report each attack, results, and number of torpedoes expended. No such reports was made regarding an attack at 1004 on Sunday morning (local) - indeed, no attacks were reported for the entire day, what must have been an extreme disappointment to the Japanese and to Yamamoto, who at one time expressed the expectation that he might get better results from the submarines than from the air attack (!!!!!!!).
Under the circumstances, after firing a torpedo that could easily be interpreted as having hit its target, the Japanese CO would have been proclaiming his success. And, there isn't a reasonable chance that such a message was sent but not received and logged, because the submarine would have transmitted the report repeatedly until it was receipt was acknowledged. And there was no chance that he could "forget" to send the report, since he would have to account for all torpedo useage upon return to base. If anything, the institutional motivation for those sub skippers would have been to report and claim credit with the boss for their agressiveness. I doubt that a message could have been sent and acknowledged and then forgotten - remember when the Japanese received the "success" message, and they instantly concluded from it (IIRC) that something like three midgets had penetrated the harbor and sunk two battleships?
Fourth is the fact that the attack could only have been delivered by one of the two submarines assigned to areas close to the channel: I-20 or I-16. Each of the Japanese submarines was assigned to a particular patrol area, and they were not to deviate from the boundaries of those areas or else risk being torpedoes by their own side. Having a defined patrol area allowed the submarines to attack all shipping in that area without fear of attacking one of their own. Combine authoritarian control by the admiral, and submarine doctrine means that you have to only consider those two submarines, and we know that they did not launch any attacks, as they were concerned about recovering their returning midgets, and spent most of their time deep evading all the US DDs that were patrolling the area. We have good reports on them, as they left their stories as part of the midget submarine tale.
Likewise, suggestions that another submarine made the attack and was later sunk make no sense. The only sub that was sunk before return was one that had a patrol area that come no closer than 60 nm to the site of the attack. Submariners did not deviate from their patrol areas.
Regarding the reported attacks against Breeze, Aylwin, and Detroit, as mentioned above, perhaps one might have been the "missing" midget torpedo, or more likely they were incorrect reports. After all, with only one torpedo left, at least three of those four reported attacks (if one includes Helm's) have to be false reports.
I know from personal experience that the acoustic conditions in the area of the islands is horrible. Plus, ships had been "pumping and dumping" off the harbor for decades. It is not unexpected that there would be lots of false contacts, and lots of depth charge attacks that brought oil and trash to the surface, and thus were reported as submarine "kills."
Given that I believe that the 5th midget expended both torpedoes outside the harbor, what then? The sub crew had a few alternatives, should they not make a rendesvous with their mother ship. Two actions are scuttling, and suicide. The third was to escape the sub, land on the beach, and mix in with the Japanese population on the island. My understanding is that the crews were given the location of a "safe house" where they could go and get help and possibly "escape and evade." I would suggest that this is what Sakamaki was trying to do when he scuttled his boat on the reef and came ashore.
SO, I see the possibilities as follows:
Least probable: after expending their torpedoes, the midget penetrated the harbor and enters the West Loch. Their intention is to get to where they can abandon the sub, scuttle it, and go to the safe house. They make the passage. They blow the boat, either with themselves inside, or they escape into Oahu and are swallowed by history. The boat is found after the West Loch disaster, salvaged, and dumped. I consider this as "least probable" since I would think that the chances of penetrating the harbor defenses undetected after the attack to be nonexistent.
More probable: with battery running down, they beach the sub somewhere around Oahu. They either scuttle & suicide, or abandon and scuttle, like Sakamaki. They are either killed getting ashore or are swallowed by history. Some years later the boat is discovered, salvaged, and dumped. If the boat was found during, say, the Korean War, there would be no reason to exploit the boat for intelligence, and every reason to keep the discovery secret, considering that the US was using Japanese bases to prosecute the Korean War, which could be considered as a violation of Japan's "no war" clause in their constitution. There was no reason the stir the Japanese pot with another reminder of the Pacific War.
So, the boat is salvaged in a "secret" operation, with the sections unbolted and cut apart probably because the whole section was too heavy for the available lifting crane (perhaps a gypsy civilian outfit - if the boat was found in shallow water a shallow-draft barge and crain combination would be needed, and such a rig would likely have a limited lifting capacity). When asked where to dump it, they used the same area as the West Lock debris field - at sea you are not allowed to dump stuff just anywhere. I remember seeing "dumping areas" outlined on many charts, although I did not look at the local Oahu charts to verify that the West Loch field was so designated on public charts (likely, not). But, if someone asked a Navy rep for this operation where to dump the debris, it is very likely that he would have directed them to the same area used previously. So, the appearance of the midget submarine in the West Lock disaster debris field could simply be a coincidence.
Level of evidence for this last scenario is nil (much like the level of evidence for the West Loch scenario). But, as a former naval officer and someone used to working within the naval beaurocracy, and having studied the decision processes of the era, it resonates with me, and tips my "probability meter" further to the right than the West Loch scenario. Could I support it in a court of law? Absolutely not.
Did I answer all your questions?
Best regards, Alan