Torpedo Attack on the USS St.
The wreck of the I-16tou
At this point, we turned to the submarine wreck itself. The condition of the wreck has been detailed in both Killer Subs in Pearl Harbor and in other articles published on this website, but suffice it to say here that the wreck was found disassembled and dumped outside the harbour. In order to have been disassembled and dumped, it had to have first been located and raised. Since there is no public record of the sub having been located and raised (as was the midget sub found in and raised from Keehi Lagoon in 1960), we assume that the event happened during wartime, when the movements and actions of certain recovery assets could be cloaked in a shroud of wartime secrecy. In the 1940s, neither the technology nor pressing need existed to locate the sub (famed and experienced explorer Bob Ballard failed in 2000 to find the midget sub sunk by the USS Ward, even though he had multiple resources and a good idea where to look) — much less raise it — from deep water outside the harbour. After all, the US Navy simply buried the second midget submarine (I-22tou) to come into their possession, so why expend resources to locate and raise another? So, by process of elimination, we felt safe in assuming that the sub was located and raised from inside the harbour. No other alternative matched the evidence of the wreck.
Since the wreck was raised from inside the harbour, then there could only be one scenario that includes a midget sub attack on St. Louis; namely, the submarine managed to work its way into the harbour after firing one or both torpedoes. Could the I-16tou have conceiveably entered the harbour? The answer is yes, but only if she entered before 0840, when the anti-torpedo nets were closed. However, by the time that St. Louis was reportedly attacked, the gate crew was alerted, the nets were closed and opened only long enough to allow cleared ships to pass through. In addition, standing orders for the special submarine crews were to proceed directly to the rendezvous point off Lanai with whatever remaining battery power their batteries retained after expending their ordnance. Given this perspective, the scenario envisioned by some historians of the midget sub working her way underneath the nets to enter the harbour after having expended both primary weapons — or even just one — does not make sense.
Regardless, some speculate that the midget sub either cut her way through the nets or squirmed underneath to enter the harbour. Lieutenant Commander Harold Kaminski, officer in charge of the net boom and defenses, had a diver inspect the nets after the attack and found no damage. He also measured the captured midget submarine and declared that "it would be extremely precarious" for a midget sub to work its way underneath the nets. Admiral Ueda concurred, saying that any attempt to navigate the submarine blind with less than 10' of clearance would be an impossible feat to manage, and for what purpose? Why risk being caught under the net trying to enter the harbour with no torpedoes? Besides, the Japanese had no information on the nets; in hindsight, we know of the scant clearance underneath, but none of the Ko-hyoteki commanders had that knowledge. As far as they knew, the nets extended to the bottom and they therefore practiced following a ship past the nets under cover of darkness.
Let's play Devil's Advocate for a moment and say that Yokoyama did fire at St. Louis, then managed his way somehow through the anti-torpedo nets with the intent of driving his boat into a major US combatant and detonating his scuttling charge to take both down. Given such determination, why was there no following attack on a target inside the harbour? Why was nothing heard from him again until 2241, when he sent his "Mission Success" message?
In my opinion, the scenario where Yokoyama entered the harbour through opened nets in the early morning, set up for an attack opposite Battleship Row, tried to exit after expending both torpedoes but was stopped by the closed nets, found a quiet place to lay on the bottom and conserve battery power and oxygen until such time that he could surface and send word of his mission back to the mother sub fits the evidence much better than any alternative.
Was St. Louis attacked by one of the Ko-hyoteki? The I-24tou was captured with both torpedoes unfired. The wrecks of the I-18tou and I-20tou were each found with both torpedoes still in their tubes. Multiple eyewitnesses observed the two torpedoes fired by the I-22tou missing their targets in the North Channel. The only midget sub whose torpedoes are unaccounted for is the I-16tou. However, no Ko-Hyoteki was capable of firing the close spread of two torpedoes that was reported by the St. Louis crew (or for that matter, by the crew of the Aylwin, Detroit or Breese). Even if she had expended only one of her two torpedoes, the I-16tou could not have entered the harbour after an attack on the St. Louis, where her wreck would eventually be found and raised. The preponderance of evidence, in my opinion, eliminates the Japanese midget submarines as being responsible for whatever the crew of the USS St. Louis witnessed.
To what, then, did the St. Louis crew react? As far as we have been able to determine, there remain two options. If the crew was wrong about the torpedo tracks, then it is possible that they were spooked by falling anti-aircraft shells fired from inside the harbour. Expecting a submarine, they found what they thought was one in the Crossbill's paravane. If in fact the trail of bubbles was real and St. Louis actually avoided a torpedo attack, then by process of elimination, those torpedoes could only have been fired by one of the fleet submarines tasked to finish off any ships that managed to escape the harbour.