Naval History and Heritage Command

Naval History and Heritage Command

ULTRA Extracts Regarding Japanese Submarine Movements, I-58 Attack, and Lessons Learned

COMNAVSECGRU 

*The ULTRA intelligence below was shared only to a small group of Allied leaders and was tightly held due to operational security concerns. Allied fears that the Japanese might find that they had broken their codes prevented this type of intelligence from being shared with ship captains.  

1. Archival Copy

DECLASSIFICATION CONSULTANT

July 12, 1988 

Memorandum 

Office of Navy  JAG

Code 145.1 

Ms. Chekonik: 

Attached are the ULTRA extracts from the investigation into the sinking of USS INDIANAPOLIS. 

These extracts are currently UNCLASSIFIED and I have appended a FORM NDW NAVSECGRU 5510/4 indicating this. 

As I indicated to you on the telephone, we do not have a complete file of the investigation and the attached pages represent the total of what we hold in our Repository on the subject of the INDIANAPOLIS’ sinking.

 

[Signed]

I.G. Newman 

[stamped] 1988 July OJAG-NAVY GENERAL LITIGATION DIV

 

[end cover page 1] 

Reviewed for declassification as authorized by Executive Order 12356 on 18 May 1988. 

Present Classification and Special Handling Requirements: Unclassified 

Reason for extension of classification (if applicable): Not Applicable 

Authority: COMNAVSECGRU (GHD/IGN) 

Next Schedule Review Date: N/A 

Items: COMNAVSECGRU FILE 5830/114: ULTRA EXTRACTS FROM THE INVESTIGATION INTO THE SINKING OF USS INDIANAPOLIS 

NDW NAVSECGRU 5510/4 (REV 8-82)

 

[end cover page 2]

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From: CINPAC PEARL

Released By:

Date 14 July 1945

TOR Coderoom:

Decoded by: Kennedy/Plumley

Paraphrased by: EXACT

Checked by: Martin

Routed by: Dodd

Dittoed by:

For Action: All Holders 35-S, COMINCH

Information: CINPAC ADV. HDQTRS., CTF 77, CINCAFPAC, COMSEVENTHFLT

Precedence: OP OP OP

Originator fill in Date and Time Group: 140232, Page 1 of 2

F-341 (6 Copies), OP-2[ ?]-3-[?]1-P (2 Copies)

 

SUBMARINE I-58 DEPARTING BUNGO CHANNEL 141700 FOR PATROL STATION MIDWAY BETWEEN LEYTE GULF AND OKINAWA. THIS IS FIRST OF 4 SUBS WHICH HAVE BEEN DIRECTED SORTIE WESTERN INLAND SEA FOR OFFENSIVE PATROLS AGAINST BLUE SHIPPING AND FOR RECONNAISSANCE. THIS IS ULTRA. FOLLOWING ARE AVAILABLE DETAILS REGARDING OTHER THREE. I-58 DEPARTING (18TH?) FOR PATROL IN VICINITY POSITIONS 500 MILES NORTH OF (PALAU?). I-47 AND I-367 DEPART 19TH FOR PATROL ON LINE BETWEEN OKINAWA AND MARIANAS THE FORMER 355 MILES FROM OKINAWA AND LATTER (450?) MILES FROM MARIANAS.  ALL SUBS CARRY 5-6 HUMAN TORPEDOS PROBABLY ON DECK AND PROBABLY IN ADDITION TO REGULAR TORPEDOES. IN APPARENT EFFOR TO INCREASE EFFECTIVENESS ANTISUB OPERATIONS IN TSUGARU-SOYA STRAITS AREA ALL MAGNETIC DETECTOR EQUIPPED PLANES OF SAEKI AIR GROUP DIRECTED 10 JULY [PAGE 2 OF 2] PROCEED OMINATO AND REPORT TO COMDR OMINATO GUARD DISTRICT ESCORT FORCE. EVIDENCE 12TH THAT RADARS URGENTLY REQUESTED FOR 30 JILLS OF NIGHT TORPEDO ATTACK UNIT OF AIR GROUP 131 BELIEVED AT KATORI.

 

[end page 3 and 4]

[page 5: Chart of Philippine Sea with estimated locations of Japanese submarines I-53, I-47, I-367, and I-58 for July 1945 around the time of the USS Indianapolis sinking.]

 

 

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From: CINPAC Pearl

Released By:

Date 18 July 1945

TOR Coderoom:

Decoded By: Pohly

Paraphrased By: EXACT

Checked By: Martin

Routed By: Dodd

Dittoed By:

For Action: All Holders 35 S, COMINCH

Information: CINPAC, CINCAFPAC, COM 7th FLEET, CTF 77

Precedence: OP OP OP

Originator till in Date and Time Group: 180209, Page One

OP-20-3-01 (2 Copies), F-341 (6 Copies)

 

THIS IS ULTRA. SUBMARINES I-47 AND I-367 DEPART EAST ENTRANCE BUNGO CHANNEL 19 JULY AT 1930 AND 2000 RESPECTIVELY FOR OFFENSIVE PATROLS AGAINST BLUE SHIPPING.  BOTH WILL BE STATIONED ON LINE BETWEEN OKINAWA AND MARIANAS FORMER ABOUT 350 MILES FROM OKINAWA AND LATTER ABOUT (450 MILES?) FROM MARIANAS AND BOTH EQUIPPED WITH HUMAN TORPEDOES.  ALL DETACHMENTS OF AIR GROUP 901 (JAPAN SEA AIR ESCORT AIR GROUP) WERE NOTIFIED 16TH THAT BLUE SUBS HAD NOT BEEN DETECTED IN JAPAN SEA SINCE 11 JULY. EVIDENCE ENEMY FOUND DESTRUCTION OF OIL PROCESSING INSTALLATIONS AT BALIKAPAPAN UNEXPECTEDLY DIFFICULT AND DISCOVERED DESTRUCTION BY EXPLOSIVES MORE EFFECTIVE THAN BURNING. EVIDENCE HEAVY DAMAGE INFLICTED IN KAMAISHI ATTACK 14TH WITH “ENORMOUS” DAMAGE TO ONE [END PAGE 1] UNSPECIFIED FACTORY AND IMPORTANT MACHINERY. EVIDENCE 12 JULY TRANSPORTATION DIFFICULTIES SERIOUSLY HAMPERING ACCUMULATION STOCKPILES OF AVIATION FUEL AND AMMUNITION IN PREPARATION FOR OPERATION HOMELAND. [END PAGE 2].

 

[end pages 6 and 7]

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From: CINPAC Pearl

Released By:

Date 19 July 1945

TOR Coderoom:

Decoded By: Demint

Paraphrased By: EXACT

Checked By: Martin

Routed By: Dodd

Dittoed By:

For Action: All Holders 35 S, COMINCH

Information: CINPAC ADV HQTRS, CINCAFPAC, COM 7th FLEET, CTF 77

Precedence: OP OP OP

Originator till in Date and Time Group: 190209, Page 1 of 2

OP-20-3-GI-P (2 Copies), F-341 (6 Copies)

 

THIS IS ULTRA. SUBMARINE I-58 EQUIPPED WITH HUMAN TORPEDOES DEPARTING EASTERN ENTRANCE BUNGO CHANNEL 191930 ENROUTE PATROL STATION ABOUT 500 MILES NORTH OF (PALO?). NIL INFORMNATION ON TRACK EXCEPT THAT AFTER 210330 COURSE WILL BE 160. SUBMARINES I-401 AND I-400 DEPARTED MAIZURU 18 JULY AT 16[?][?] AND 18[?]0 RESPECTIVELY ARRIVING OMINATO MORNING 20TH. THESE SUBS COMPRISE FORCE TO CARRY OUT “ARASHI” OPERATION (ATTACK ON ULITHI ANCHORAGE INVOLVING USE OF SIX SUB-BORNE AIRCRAFT). DEPARTURE DATE FROM OMINATO UNKNOWN. ENEMY PLANNING LAY MINES OFF EXPECTED INVASION BEACHES IN HOMELAND USING NEW TYPE MINE ESPECIALLY DESIGNED AGAINST LANDING CRAFT AND LAID IN WATERS WHERE DEPTH IS LESS THAN 15 METERS (8.2 FATHOMS). COMPLETION THIS MINING IN KYUSHU SHIKOKU AREA PLANNED BY END OF AUGUST AND IN UNSPECIFIED SECTION [END PAGE 1] OF TOKYO AREA BY END OF SEPTEMBER. EVIDENCE 15 JULY COMDR 5TH AIR FLEET REQUESTED INSTALLATION OF SEARCHLIGHTS ON SUICIDE ATTACK PLANES. [END PAGE 2].

 

[end pages 8 and 9]

29 July/2238

JN-25-P-091

36

 

TOP SECRET ULTRA

 

From:  SA TE KO 4

To:  WA RO E 04 (A SU SO 7) (Advance Expeditionary Force)

Info: SU SA SA 86 (RI KU O 0) (Tokyo Bureau of Military Preparations); HO FU NO 98 (KO E YA 5) (Combined Naval Force Headquarters)

ADVANCED EXPEDITIONARY FLEET DESOPORD #102.

I-53 (26971), I-58 (16595), I-47 (81276) and I-367 (28271) will operate respectively within about 50 miles of the following four positions in accordance with COMBINED NAVAL FORCE DESOPORD #141 for purpose attack against the supply line between Leyte and Okinawa and also to intercept the enemy striking force, should it return.

GZ Comment: All positions are unrecovered grids.  We are trying to do something with them.

(GZ#13949-H0NEGAT 300136-300139-COMB-FRUEF-DI)

GI Comment: Despatch of 0952, 13 July (item 29, Pages 22 and 23, RI Summary 131300/Q July) organized a KAITEN SUICIDE ATTACK FORCE with the above four submarines, and directed them to sortie as soon as preparations were completed and carry out attacks on enemy shipping and ascertain the enemy situation. All were assigned operating areas in the Philippine Sea.  I-53 was scheduled to depart Bungo Suido on 14 July.  The other submarines were all eventually scheduled to sortie on the 19th.

 

IMPORTANT:- The information contained herein is not to be reproduced or referred to in any manner which may disclose its source.

 

Page 20, July 30 A.M.

 

[end page 10]

SOUTHERN JAPANESE EMPIRE AREA

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30 July/0048

JN-25-P-91

62 

From:  SA TE KO 4

To:  NO FU TE 27 (RI KU O 0) (Navy Vice Minister); MA SO MA 01) (KO E YA 5) (COMBINED NAVAL FORCE Headquarters); SI U RI 14 (NE KI TA 1) (Commander ADVANCE EXPEDITIONARY FORCE)

 

From Captain Submarine I-58 (16595).

29th at 2332 attacked and sank one ____. Sinking confirmed. 29th ____. Position of hits (unrecovered grid).

(FRUPAC-300756-DISC0DI)

GI Comment: Despatch of 29 July/2238 (item 36 page 20, RI Summary 300500/Q July) ordered Subs I-58, I-53, I-47, and I-367 to carry out attacks against the supply line between Leyte and Okinawa and also to intercept Blue striking force if it should return.

NEGAT identifies: RI KU O 0- Tokyo Bureau of Military Preparations.

 

IMPORTANT: - The information contained herein is not be reproduced or referred to in any manner which may disclose its source.

 

Page 41, 31 July P.M.

 

[end page 11]

 

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From: CINPAC Pearl

Released By:

Date 31 July 1945

TOR Coderoom:

Decoded By: Campbell

Paraphrased By: EXACT

Checked By: Martin

Routed By: Sprague

Dittoed By:

For Action: All Holders 35 S, COMINCH

Information: CINPAC ADV HQTRS, CINCAFPAC, COM 7th FLEET, CTF 77

Precedence: OPERATIONAL PRIORITY

Originator till in Date and Time Group: 302049, PAGE 1 OF 3

OP-20-3-GI-P (2 Copies), F-341 (6 Copies)

 

AT 301142 COMDR SIXTH AIR ARMY IN KYUSHU ANNOUNCED PLAN TO ATTACK IEJIMA AND NORTH AND CONTROL AIR FIELDS ON OKINAWA 1 AUGUST AT [unreadable] AND [unreadable] USING ABOUT 10 HEAVY BOMBERS EACH TIME. THIS IS ULTRA WESTERN PACIFIC SUMMARY 30 JULY. BLUE CARRIER FORCE APPARENTLY LOCATED ABOUT NOON BY ARMY AIRCRAFT. MORNING THIRTIETH COMDR SEVENTH BASE AIR FORCE OUTLINED PLAN FOR ATTACK IN EVENT SURFACE UNITS SHOULD CARRY OUT BOMBARDMENT IN AREA BETWEEN ISE BAY AND KASHIMA NADA (TOKYO AREA) THAT EVENING. PREPARATIONS ALSO MADE FOR DAYLIGHT ATTACK AGAINST BLUE CARRIER FORCE BY 10 JUDYS AND 10 GRACE OF THIRD AIR FLEET SHOULD CARRIER FORCE STRIKE AGAIN THIRTYFIRST. RECONNAISSANCE OF OKINAWA AREA CARRIED OUT THIRTIETH APPARENTLY BY ARMY AIRCRAFT FROM KYUSHU BETWEEN 1200 AND 1230 AND AGAIN [END PAGE 1] AT 1300 WITH SHIPPING REPORTED IN BUCKNER BAY, KERAMA ANCHORAGE, AND OFF KADENA. SUBMARINE I-53 SENT 1 HUMAN TORPEDO AGAINST BLUE CONVOY OF 1 MEDIUM AND 7 SMALL SHIPS PLUS 3 DESTROYERS HEADED SOUTH AT 241442 IN UNKNOWN POSITION IN PHILIPPINES SEA. AT 1515 SUB HEARD 1 EXPLOSION. COMMENT: TIME CHECKS WITH SINKING OF UNDERHILL. SAME SUB SENT 2 HUMAN TORPEDOES AGAINST BLUE CONVOY HEADED SOUTH IN UNKNOWN POSITION AT 291446. ABOUT 1715 SUB SAW LARGE COLUMN WATER ACCOMPANIED BY LOUD EXPLOSION. COMMENT: NOTE 2 HOUR AND 29 MINUTE TIME INTERVAL BEWEEN LAUNCHING HUMAN TORPEDOES AND EXPLOSION. SUBMARINE I-58 ALSO CARRYING HUMAN TORPEDOES REPORTED SINKING 1 UNIDENTIFIED TYPE BLUE VESSEL AT 292332 IN UNKNOWN POSITION IN PHILIPPINE SEA.  COMMENT: MEANS NOT INDICATED. AFTERNOON TWENTYNINTH COMDR AIR [END PAGE 2] FLOT 29 IN FORMOSA REPORTED RESULTS OF SUICIDE ATTACKS PROBABLY IN CONNECTION WITH TACHIBANA OPERATION NIGHT OF 28-29TH 4 SUICIDEERS REPORTED TO HAVE MADE SUCCESSFUL ATTACKS. 1 UNIDENTIFIED SHIP CLAIMED SUNK 40 MILES SOUTH OF KUMJIMA AND ANOTHER CLAIMED SUNK IN KADENA AREA. AT 301059 SAME COMDR ORDERED TACHIBANA OPERATION SUSPENDED. DESTROYER KAMIKAZE REPORTED ENGAGE 1 B-24 AT 301310 IN 8-36N 102-36E. CINC COMBINED INDICATED IN TOKYO AREA. [END PAGE 3]

 

[end pages 12, 13, and 14]

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Headquarters of the Commander in Chief

Navy Department

Washington 25, D.C.

 

3 August 1945

 

MEMORANDUM FOR F-00 

Subject:  U.S.S. INDIANAPOLIS, Sinking of.

 

  1. The following information derived from ULTRA sources indicates that four Japanese submarines were known to be operating between Okinawa and Leyte Gulf, and that I-58 probably was responsible for the sinking of subject ship

    1. On 13 July, CINC 6th Fleet organized a KAITEN Suicide Attack Force comprising submarines I-53, I-58, I-47, and I-367.  These submarines were directed to sortie from BUNGO Suido between 14 and 19 July to patrol assigned areas in the Philippine Sea.  The first 3-named submarines were to carry 6 KAITEN each, the I-367 was to carry 5.  The patrol areas assigned were as follows:

      1. I-53 – Vicinity of midpoint between Leyte Gulf and Okinawa.  (KAITEN  from this submarine probably sank UNDERHILL (DE) on the 24th.)

      2. I-58 – Vicinity of a point 500 miles north of (Palau?).

      3. I-47 – On a line between Okinawa and the Marianas, about 350 miles from Okinawa.

      4. I-367 – On a line between Okinawa and the Marianas, about (450?) miles from Marianas.

    2. At 2922381, these submarines were ordered to shift their patrol areas in order to attack the Blue supply line between Leyte Gulf and Okinawa and to intercept the Blue Striking Force, should it return through this area.

    3. At 3000481, I-58 reported that at 2923321, she attacked and sank one ______.  She also states that the sinking was confirmed.  (The position was included, but has not been recovered yet.)  Comment:  The dispatch reporting the sinking of INDIANAPOLIS states that she was torpedoed and sunk on Sunday night (29th).  Available information indicates that she was northeast of Leyte Gulf.  Of the four submarines operating between Leyte Gulf and Okinawa, I-58 is estimated to be in the southernmost position and nearest to Leyte Gulf.

 

Very respectfully,

 

W.R. Smedberg, III.

6 August/0816 1945

JN-25-R-101

 

[end page 15]

TOP SECRET

From: CINPAC ADV HQ

Released By:

Date 11 August 1945

TOR Coderoom: 1627

Decoded By: C Strong

Paraphrased By: Walp

Checked By: Lenihan

Routed By:

Dittoed By:

For Action: COMINCH

Information:

Precedence: Routine RRRRRR

Originator till in Date and Time Group: Page 1 of 2, 110457, NCR 683 

(FROM CINCPAC ADV HQ TO COMINCH) 

TOP SECRET. YOUR 072007. USE OF RADIO BY GERMAN SUBS IN ATLANTIC PERMITTED FREQUENT DIRECTION FINDER POSITIONS AND TRACKING WITH SOME DEGREE OF ACCURACY IN ESTIMATING FUTURE LOCATIONS. JAP SUBS IN PACIFIC RARELY USE RADIO WITH RESULT THAT WE NOW AVERAGE ABOUT 1 DF POSITION IN 3 MONTHS. THIS PRECLUDES ISSUE OF PERIODICAL ESTIMATES ON NON ULTRA LEVEL. SUBMARINE CONTACT REPORTS ARE IMMEDIATELY RETRANSMITTED ON FOX BROADCASTS. CONTACTS CONSIDERED SUFFICIENTLY PROBABLE TO WARRANT ASW ACTION ARE INCLUDED IN BLUE SUMMARY OF WHICH YOU ARE AN ADDRESSEE. POSITIONS RECEIVED BY ULTRA ARE ONLY DEFINED AS GENERAL LOCALITIES. JAP SUBS PATROL AT CONSIDERABLE DISTANCE FROM POSITIONS GIVEN. SUB WHICH ATTACKED INDIANAPOLIS WAS APPARENTLY 260 MILES FROM ASSIGNED POSITION. ALL SHIPPING TO AND FROM OKINAWA AND TO AND FROM IWO JIMA [END PAGE 1] IS ESCORTED. PASSENGER SHIPS WITH MORE THAN 500 PASSENGERS WHICH MAKE LESS THAN 18 KNOTS ARE ESCORTED BETWEEN ENIWETOK AND PHILIPPINES. SINCE INDIANAPOLIS ATTACK ALL SHIPS WITH OVER 500 PERSONS ABOARD ARE ESCORTED BETWEEN ULITHI AND PHILIPPINES REGARDLESS OF SPEED. CONSIDER IT ADVISABLE TO CONTINUE RELATIVELY HEAVY ESCORTS ON ROUTES TO MORE NORTHERLY POSITIONS WHERE CONCENTRATION OF JAP SUBMARINES IS BELIEVED TO BE MORE LIKELY EVEN THOUGH THIS PRECLUDES ESCORTS OF SOME TYPES IN ROUTES IN SOUTHERN AND EASTERN AREAS. IF ENEMY SUBMARINE IS FOUND TO REMAIN IN PARTICULAR LOCATION SHIPPING WILL OF COURSE BE DIVERTED. BUT WHEN SUB POSITION CANNOT BE DEFINITELY DETERMED EXCEPT BY ACTUAL CONTACT, SINCE MANY REPORTED SOUND AND VISUAL CONTACTS ARE FOUND TO BE FALSE, AND SINCE SUBS MOBILITY PERMITS WIDE VARIATION IN POSITION BETWEEN ATTACKS IT IS BELIEVED THAT IF DIVERSIONS WERE INITIATED AS RESULT OF EACH INCIDENT THIS WOULD CAUSE A GREAT AMOUNT OF CONFUSION, CONSIDERABLE DANGER OF COLLISION, AND INTERRUPTIONS IN SCHEDULES WHICH WOULD BE OF GREATER VALUE TO JAPANESE THAN THE INFREQUENT SUCCESSFUL ATTACKS. 

COMINCH. . . COPIES 1 TO 8 INCL.

 

[end pages 16 and 17]

Navy Department
OFFICE OF THE CHIEF OF NAVAL OPERATIONS
Washington 25, D. C.

 

Op-32P1

TOP SECRET-ULTRA

 

31 October 1945

 

MEMORANDUM FOR CAPTAIN SMEDBERG:

 

Subject: U.S.S. INDIANAPOLIS, sinking of.

 

            1. On 13 July ULTRA information disclosed the imminent departure of four Japanese submarines from the Western Inland Sea for patrol against Blue shipping and for reconnaissance purposes.  Submarines involved were: I-47, I-53, I-58, and I-367.  The initial patrol area assigned to these submariners as indicated by ULTRA sources is shown on the accompanying chart.  All four submarines sortied between 14 and 19 July.

            2.  I-58, the submarine which is believed responsible for the sinking of the U.S.S. INDIANAPOLIS, sortied from the eastern entrance to Bungo Suido at 192000I July to operate in the “sea area west of the Marianas Islands”.  Earlier messages gave her operation area as 500 miles north of Palau (?).

            3. On 29 July all four submarines were ordered to operate respectively within approximately 50 miles of four unknown positions for purposes of attack against the Blue supply line between Leyte and Okinawa, and to intercept the Blue striking force should it return to Leyte.  (T.F. 38 was conduction strikes against the Kure area on 28 July and evidence strongly indicates that the Japanese expected 3RD FLEET units to return to Leyte upon completion of the strikes.)

            4. I-58 reported at 300048I July that at 2923321 she had attacked and sunk one____.  As this time coincides with the time of the sinking of the INDIANAPOLIS, and as no other submarine attacks were reported, it is believed that no doubt exists that U.S.S. INDIANAPOLIS was sunk by I-58.

            5. The foregoing information was available to CINCPAC and COM7THFLEET.

 

Respectfully,

[signed]
JAMES G. WATKINS.

 

[end page 18 and ULTRA collection]

Published:Wed Jul 06 09:40:42 EDT 2016