by Tom Taylor
Copyright © 2010 Tom Taylor
"We all thought that there was another submarine in the harbor at the time, but that was never discovered and I do not think there was another submarine in there."
- Admiral Husband E. Kimmel, Commander-in-Chief, US Fleet, in testimony given to the Roberts Commission, 27 Dec 1941
"The best evidence we have indicates that only one got in. There was some evidence that might lead to the supposition that a second submarine got in, but on further research my people told me they did not think there was more than one."
- Admiral Thomas B. Inglis, Chief of Naval Intelligence, in testimony given to the Joint Committee on the Investigation of the Pearl Harbor Attack, 16 Nov 1945
In conducting a post-mission reconstruction of the events surrounding the Japanese midget submarine I-16tou, my colleague Parks Stephenson and I reviewed every document and eyewitness account that was accessible. Nominally, mission specialists depend upon debriefing the crews themselves for their inputs, conducting photoanalysis of any images taken during the mission prosecution, reviewing sensor logs to marry up crew inputs and print out automated "War Diaries" that are recorded within the combat system in use and inaccessible to the crews for alteration. In the case of the I-16tou, we were limited to after-action reports, eyewitness accounts, and tower logs from the Pearl Harbor Navy Yard Tower.
After Action Reports
A careful study was made of every After-Action Report (AAR) submitted by units that were participants in the Pearl Harbor attack. In many cases, several of the AARs had to be reviewed multiple times in order to fully understand both what the crews were saying and how what they reported married up with other information. The biggest problem we found (which can be related to by most historians) were the time estimates for certain events. All of the AARs were submitted by commands days, if not weeks, after the actual events of December 7, 1941, occurred. For a good portion of these inputs, times for events were an approximation by crews, as best as they could remember. In other sections of the AARs, times for events were either right on or, as we referred to it in the Navy, "close enough for government work." How to differentiate which times were which was not difficult to do.
To determine the accuracy of time inputs within an AAR, one had to first determine if the reporting unit was in a deployable state or not. A deployable state would be a condition where the bridge of a ship was manned properly and set to make way. If the unit was manned properly, then a log taker was assigned to record events as they were reported. Time inputs would be based on the ship’s chronometers which were traditionally set without fail at 0800 every morning. This setting of the clocks is conducted only on major combatants and not necessarily on smaller vessels, such as tugs or patrol boats. Therefore, if an event in an AAR was logged at a time when the ship was considered underway (bridge manned properly), then the times of that event could be considered fairly accurate; e.g., the time logged by the destroyer USS Monaghan (DD-354) when she rammed the I-22tou.
It was found that a good deal of the AARs were submitted with partial reconstruction times based upon memories of the events and/or partial chronometer inputs during a time when the bridge was not properly manned or events were confused by sudden nature of the attack. These time inputs are therefore much less reliable.
The most credible timeline was maintained in the logs of the Pearl Harbor Navy Yard Signal Tower. Here we find events within the line of sight of the tower crew (which encompassed most of the harbor) logged in a consistent, meticulous manner. More importantly, each entry was time-stamped, using the tower's clock as a constant time reference. These log inputs establish a credible and accurate timeline on events taking place before, during and after the attack on Pearl Harbor. It would prove to be a critical reference in our post-mission reconstruction of the I-16tou.