This article is printed as it appeared in the U. S. Submarine Veterans of WWII magazine Polaris vol. 43, No. 6 December 1999.  The Raton version is by RADM J. W. Davis, USN Ret who was the Commanding Officer of the Raton at the time of the incident.  The Lapon version is by CAPT R. C. Gillette, USN Ret who was the Executive Officer and Navigator at the time of the incident.
During World War II there was only one confirmed instance of a U. S. submarine firing on another U. S. submarine.  It happened on the morning of 27 May 1944 in the South China Sea.  The two submarines involved were Lapon (Cdr L.T. "Steamie" Stone '29) and Raton on which I was the skipper.  At the time Raton was patrolling in an area adjacent to Lapon and Gunnel (Cdr. John S. McCain, Jr. '31) areas.  Since I never kept a diary or have war patrol reports available for reference, what I am now writing is from memory and must be accepted in that light.  After all this incident occurred almost 50 years ago.

A day or two before the incident we had received a "ultra" message (we used to refer to them as "burn before reading messages."  As I recall it started off "For Jim Davis eyes onl."  At that point the decoding officer stopped and brought the message and decoding machine to me and I finished decoding the message.  The message reported a small Japanese RO class submarine en route from Singapore to Japan.  It gave the routes, dates, times, and positions.  I made notes and then burned the decoded message in the ash tray on the wardroom table.  Next I passed this info to the Exec. who was also at the time Navigator, on a "need to know" basis.  He was the only other person on board who was privy to this info.  We then plotted it on a chart and set a course to intercept as I considered this message to me was for Raton's action only.  It meant that we would have to enter Lapon's area and I assumed that she was either on her way home or at least had been alerted to our probable entry into her area.  As I recall I never gave it any further thought other than the normal lookout for her when we entered her area.

On the morning of the incident I had told the navigator that we would delay our normal early dawn trim dive in order that he could obtain a good fix as we were approaching the projected tract of RO submarine.  Later on we were still on the surface when he called down from the conning tower and said he had a good fix and requested permission to change course 30 degrees to the right.  It was granted and I started to the bridge.  At the time I believe we were on course almost due west.  I had just started up the ladder in the Control Room and I could feel the ship turning when the ship was shakened by two strong underwater explosions.  My first reaction was we had been cought on the surface by a plane.  I hurried to the bridge and was surprised that the bridge personnel had not felt the explosions, but the J.O.O.D. did say he thought he might have seen a thin oil or air bubble slick about 1000 yards on the port beam.  Anyway we continued on and dove on the projected track of the RO submarine and commenced a periscope watch.

Early in the afternoon we made contact with the RO submarine and started an attack approach.  However, just before we were ready to fire she made a large turn away and we did not fire.  We surfaced later and started an end-around for a night surface attack.  Again we were not successful.  As we were going in for an attack the sub turned sharply away and dove.  We broke off contact and resumed our normal patrol.  We were also very close to the southern edge of Gunnel's area.

A little while later I was down in the wardroom preparing a message to headquarters in Australia about our day's activities when the Communications Officer handed me a message.  It was from Lapon and as I recall it started off "Oh my God X Missed repeated missed possible Uncle Sugar submarine etc."  A quick check of her position and the mystery of the two early morning explosions was solved.  I couldn't believe it, and as I recall I was a little upset.  I started my message to Headquarters "Poor shot X Missed repeat missed Japanese Ro submarine, etc."  After I had sent the message I realized that I might have violated coding instructions.  Six months later, while I was on duty in Pearl Harbor, the Director of Naval Communications informed me in no uncertain terms that I had indeed violated coding instructions.

After we returned to Australia I don't recall ever discussing the incident either with Adm. Christie or any member of his staff.  Neither did I ever discuss it in detail with "Steamie" Stone whom I had known only slightly up to that time.  However we became good friends and continued so even after his retirement and up to the time of his death.  I am sure that the reason that there were no searching discussions of the incident was the "very nature of the beast" - "ultra."  It was strictly taboo subject for discussions - an on a "need to know basis" only.  No reference or hints of "ultra" would ever be made in the war patrol report.

The reason I am writing this account after so many years is that in a recent book (1989) and account of the incident is recorded in which it is stated that Raton "went into her (Lapon) area" with no explanation why.  It further stated that Raton was "moving along underwater" when the attack occurred, when in fact Raton was cruising on the surface.  In none of the post war reports I have read has the reason why Raton was in Lapon's area been thoroughly recorded.  In fact in all of the reports there is a strong inference that Raton was at fault.  On the basis of that "ultra" message to me I believed that we were required to enter Lapon's area in order to carry out orders.  I further believe that the chief cause of this unfortunate incident probably had its birth in the Staff Headquarters back in Australia.