Identifying the Wreck
by Parks Stephenson
Text and colour images copyright © 2010 Parks Stephenson
Most of what we could learn had to come from the wreck itself, because our searches throughout the archives had yielded no new information. We knew that it had to be a Type A Ko-hyoteki special submarine that participated in the Pearl Harbor attack because of the following features:
These features had been compared against Japanese midget subs documented at Sydney, Guadalcanal, Okinawa, Guam, Kiska, Papua New Guinea, Philippines, and Kure. No other sub had the same combination of features that are found on the Pearl Harbor subs, as exemplified by the I-24tou, that today is on display at the National Museum of the Pacific War in Fredericksburg, Texas. The single-ring propeller guard was seen on a sub raised from Okinawa, but that sub also had enlarged rudders (along with other features that did not match the Pearl Harbor subs). There is no documentation on the subs that participated in the Madagascar attack, but there is absolutely no reason to believe that any of those subs were salvaged, much less brought to O'ahu.
The team of Japanese experts, led by Kazuo Ueda (Vice Admiral, JMSDF, retired), concluded upon examination of the wreck that it was without a doubt the missing sub from the Pearl Harbor attack. For them, the "figure-8" net cutter was the deciding factor. Even if the other two sections were not unique, the bow section certainly was, and if we had the bow section, then we had proof of the sub's presence. The previous theory that this 3-section wreck was a war trophy brought back from another Pacific battleground lost a lot of credibility after this find. Besides, no evidence could be found of any submarine being brought to O'ahu from elsewhere...even the Type A special submarine on display at the Submarine Force Museum in Groton, Connecticut, does not appear to have stopped in O'ahu on its way to the United States.
With identification of the wreck as that of a Pearl Harbor sub, we could make a credible assumption on what sub it could be. The radio message received at 2241 (local time) by Kichiji Dewa aboard I-16 was the "to-ra" code, meaning "Surprise attack successful." The torpedoes on 4 of the 5 midget subs have been accounted for and none of those hit any targets. It is difficult to make the case that any of the commanders of those boats would send "to-ra" without firing their weapons (I-22tou did fire its torpedoes, missing both intended targets, and the crew was killed during the ensuing action). Only the torpedoes from I-16tou could not be positively accounted for. Therefore, the only boat that might conceivably have sent a "success" message would have been I-16tou. Coupled with the fact that each midget sub was assigned its own discrete frequency with which to exchange signals with its mother sub, the "to-ra" could only have come from Yokoyama in I-16tou. Since this new wreck is the only sub out of the 5 with missing torpedoes, the process of elimination dictated that it had to be the missing I-16tou.