U.S.S. SENNET (SS-408) — war patrol report SS-408_SENNET.pdf

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START OF REEL
JOB NO. [HANDWRITTEN: H-108]

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OPERATOR [HANDWRITTEN: M. Monroe]
DATE [HANDWRITTEN: 2/13/80]

THIS MICROFILM IS
THE PROPERTY OF
THE UNITED STATES
GOVERNMENT

[SEAL: DEPARTMENT OF DEFENSE, UNITED STATES OF AMERICA]

MICROFILMED BY
NPPSO-NAVAL DISTRICT WASHINGTON
MICROFILM SECTION

REEL TARGET - START AND END
NDW-NPPSO-5210/1 (6-78)

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[HANDWRITTEN: SENNET (SS-408)
World War II:
PATROL FILE
ACTION REPORTS
ALL MATERIAL ON THIS REEL Is DECLASSIFIED
FOR DECK LOGS AUGUST 1944 - DECEMBER 1945
CONSULT NATIONAL ARCHIVES WHICH HAS CUSTODY.

J.A. KOONTZ]

— page 3 —
Office of Naval Records and History
Ships' Histories Section
Navy Department

HISTORY OF USS SENNET (SS 408)

The submarine SENNET was launched on 6 June 1944 with Mrs. Roscoe
W. Downs, five star mother of World War II acting as sponsor. Little
more than two months later, 22 August, the new submarine was put into
commission at the Portsmouth, New Hampshire Navy Yard and Commander
George E. Porter, USN, assumed command.

The period from 21 August to 18 September was devoted to train-
ing exercises off Portsmouth, New Hampshire, which included submerged
and surface practice approaches on a target vessel, battle surface
practice, practice dives, emergency drills and ship handling drills,
at the expiration of which time three days were spent operating off
Provicetown, Massachusetts, conducting standardization runs for speed
and turning circle characteristics. From 21 September to 6 October
SENNET conducted a simulated war patrol of one week's duration off
Portsmouth, New Hampshire. Training exercises were continued at New
London, Connecticut, and in Long Island Sound, and off Balboa, Canal
Zone, as the new submarine proceeded to the Pacific war zone. On 29
November she was detached from the Atlantic Fleet and became a member
of the Pacific Fleet enroute Pearl Harbor. On 5 January 1945, SENNET
departed Pearl Harbor on her first war patrol.

From Pearl Harbor SENNET pointed her long nose toward Midway
Island, paused there for minor repairs on the 9th, and got underway
the following day enroute for a patrol area north of the Bonin Islands.
Arriving the patrol area on the 21st of January, SENNET made a night
surface attack on the same group at dawn. No hits were scored on
either attack. However, the period from 22 to 26 January proved more
lucrative-one 500 ton picket boat was sunk and one 500 ton picket boat
was damaged. SENNET departed station on the 28th and put in at Saipan
on the 31st. The submarine combat insignia was awarded SENNET's
officers and crew for the successful completion of this patrol.

SENNET departed Saipan on 7 February for her second war patrol
in company with the submarines HADDOCK and LAGARTO, the mission of
this coordinated group being to destroy Jap picket boats in open waters
South of the Japanese Empire. Arriving the designated area on 11
February, the three subs wasted no time in getting to the task at hand.
Less than two days after arrival they knocked off two 300 ton picket
boats by combined gunfire. On the 15th SENNET parted company and went
to patrol off Ki Suido.

The following day she sunk an 1800 ton Fubuki class Jap destroyer
with two torpedoes from her stern tubes. 16 February to 5 March was
a period of poor hunting for SENNET during which time she engaged in
the dull routine of patrolling station. She put in at Guam on 9 Marvh,
thus completing her second war patrol. The submarine combat insignia
was awarded SENNET's officers and crew for the successful completion
of this patrol.

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- 2 - USS SENNET (SS 408)

SENNET got underway for her third patrol-back to Kii Suido again
on 3 April, arriving in the area on the 9th, and firing four torpedoes
at Jap PT boats--no hits--on the 16th. Two days later she ran into
trouble and was forced to dive when a Jap plane gave her a going over
in a strafing attack. SENNET struck back the following day, however,
by sinking a medium AK (5,200) tons and one escort in a submerged ap-
proach off Kii Suido. On the 22nd, while acting as life guard for an
air strike, SENNET attempted to pick up one fighter pilot who bailed
out nearby, but he drowned before she could get to him. On the 28th
she sunk a naval cable layer (3,000) tons in a submerged approach off
Miki Saki, but her luck ran out on the first day of May when she mis-
sed a Jap destroyer with five torpedoes and took a bad shaking up
when the perturbed Jap dropped several depth charges too close for
comfort.

On 16 May she tied up at Pearl Harbor, completing her third war
patrol, for which her officers and crew were awarded the submarine
combat insignia for successful completion of the patrol.

Lieutenant Commander C. R. Clark, USN, relieved Commander G. E.
Porter as commanding officer of SENNET on 30 May 1945.

With her new skipper at the conn SENNET got underway for her
fourth war patrol on 1 July, arriving Guam on the 13th, where she
conducted special training until the 16th, when she took departure
for Tsushima Straits and the Sea of Japan. By the 27th the Japanese
became aware of the fact that SENNET was holding a Field Day in their
back yard. Her box for that day is as follows: One large AK (7,500
tons) sunk off Henashi Saki in a night surface approach, during which
attack three torpedoes hit the mark; the following morning a group
of three merchant vessels were attacked in a submerged approach off
Shiose Saki; two of them were sunk, one a 7,500 ton AK, the other a
small 2,000 ton AK, number three managed to dodge SENNET's torpedoes
and escape. Two days later -- 30 July, a large 7,500 ton AK was sunk
in a submerged approach off Motsuta Misaki. On the 31st SENNET de-
parted station and the Sea of Japan through La Perouse Straits, com-
pleting her fourth successful patrol at Saipan on 9 August. The sub-
marine combat patrol insignia was awarded SENNET's officers and crew
for the successful completion of this patrol.

During her comparatively short war career, SENNET made four war
patrols, sinking eleven ships totalling 35,700 tons and damaging one
ship of 500 tons, and her officers and men lived to tell about it.

By Directive dated March 1946, USS SENNET (SS 408) has remained
on active status attached to the U. S. Atlantic Fleet.

SENNET is a BALAO class submarine with a surface displacement of
1,525 tons and an overall length of 311 feet.

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- 3 - USS SENNET (SS 408)

USS SENNET earned four Battle Stars on the Asiatic-Pacific Area
Service Medal for participating in the following operations:

1 Star/Iwo Jima Operation
     Assault and Occupation of Iwo Jima -- 15 February to 16 March
     1945

1 Star/Okinawa Gunto Operation
     Assault and Occupation of Okinawa Gunto -- 24 March to 30
     June 1945

1 Star/Submarine War Patrol -- Pacific -- 8-31 January 1945

1 Star/Submarine War Patrol - Pacific -- 1 July to 9 August 1945.

*****

Stencilled November 1946
Restencilled August 1951

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U.S.S. SENNET (SS408)

                                                                Care of Fleet Post Office,
                                                                San Francisco, California,
                                                                31 January 1945

SS408/A16-3
Serial: (03-45)
C-O-N-F-I-D-E-N-T-I-A-L
                                                                [STAMP: DECLASSIFIED-ART. 0445, OPNAVINST. 5...
                                                                BY [HANDWRITTEN: OPQ9B/k] DATE [HANDWRITTEN: 6/16/72]]

From:           The Commanding Officer.
To:             The Commander-in-Chief, U. S. Fleet.
Via:            (1) The Commander Submarine Division 81.
                (2) The Commander Submarine Squadron EIGHT.
                (3) The Commander Submarine Force, Pacific Fleet.
                (4) The Commander-in-Chief, U. S. Pacific Fleet.

Subject:        U.S.S. SENNET - Report of War Patrol Number ONE.

Enclosure:      (A) Subject Report.
                (B) Track Chart (Comsubpac only).

                1. Enclosure (A), covering the First War Patrol of this vessel
conducted in the PONINS area during the period from 5 January 1945 to 31
January 1945, is forwarded herewith.

                                                                G. E. PORTER.

[HANDWRITTEN: FILMED]
[HANDWRITTEN: 108480]

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U.S.S. SENNET (SS408)
C-O-N-F-I-D-E-N-T-I-A-L

(A) PROLOGUE:

SENNET commissioned 22 August 1944, at the U. S. Navy Yard,
Portsmouth, N.H. Sixteen (16) days training period which included
standardization runs off Provincetown, Massachusetts.

6 August 1944, departed Portsmouth, N.H. Arrived U.S. Naval
Torpedo Station, Newport, R.I. Conducted contract torpedo trials.

11 October 1944, departed Newport, R.I. Arrived U.S. Submarine
Base, New London, Conn. Six (6) days training period.

23 October 1944, departed New London, Conn. 24 October 1944,
arrived U.S. Naval Mine Warfare Test Station, Solomons, Maryland.
Conducted experimental torpedo and mine firings.

11 November 1944, departed Solomons, Maryland. 19 November
1944, arrived Coco Solo, C.Z. and passed through Panama Canal.
Moored Submarine Base, Balboa, C.Z. Five (5) days training period.
28 November 1944, reported CinCPacFlt for duty.

29 November 1944, departed Balboa, C.Z. 16 December 1944,
arrived Submarine Base, Pearl Harbor, T.H.

Minor refit at Submarine Base. Topside armament increased.
Now mounting two five inch, two forty caliber, and three fifty
caliber guns. Seven (7) days training period.

(B) NARRATIVE:

5 - 9 January 1945.

1330VW/5 Departed Pearl in accordance with ComSubPac
Secret Operation Order No. 10-45.

1130 X/9 Entered Midway. Minor repairs.
Topped off with fuel.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

10 January 1945.

0830 (Y) Departed Midway for patrol area north of the Bonin
         .Islands.

11 - 19 January 1945.

         Daily control drills, battle problems, and training
         dives enroute area.

20 January 1945. (All times will be ITEM unless otherwise specified).

0200 (I) Entered area.
0713 Submerged to adjust trim.
0722 Surfaced.
1940 Sighted two patrol boats. (Ship Contacts No. 1
         and No. 2).
2018 Stopped. Lying too until daylight to investigate
         ship contacts.

21 January 1945.

0212 Radar contact range 18,000 yards. Commenced
         tracking. (Ship Contacts Nos. 3, 4, 5, and 6.).
0425 Problem solved. Base course 340°T. Speed 8 knots.
         Target was a large tanker escorted by three ships
         which appeared to be torpedo boats or mine sweepers.
         Built up to full power and started in. Escorts
         positioned, one on port bow, one on starboard bow,
         one astern.
0445 Slowed to standard speed. Passed 1,000 yards astern
         of starboard bow escort.
0448 Range 1400 yards. Distance to track 1,200 yards.
         Track angle 70 degrees starboard. Commenced firing.
         Fired four torpedoes. First two to hit and the last
         two with an offset spread.
0450 Ordered left full rudder and cleared target. No
         hits.
0458 Heard two explosions. May have been torpedo
         explosions at end of run. Do not believe they were
         depth charges since the target did not change base
         course and I assumed we were undetected.
0500 Commenced end around to gain position ahead for
         submerged attack. Daybreak will prevent another
         surface attack. Only two torpedoes remaining
         aboard.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

0700
0759
Submerged. Battle Stations. Commenced approach.
Range 1,500 yards. Track angle zero. Fired No. 1
tube. Target zigged 20 degrees to his right.
Checked fire and changed fire control problem to
new set up.
0801
Fired No. 2 tube and started deep. Escorts very
close aboard. No hits.
0807
Two depth charges. Not too close.
0923
Surfaced to send contact report. No torpedoes
remaining. Antenna trunk grounded out.
0933
Sighted mine sweeper escort searching area of
attack. He sighted us and headed toward us.
0936
Submerged and headed toward escort.
[HANDWRITTEN: man]
[HANDWRITTEN: bites]
[HANDWRITTEN: dog]
The closest range
attained was 5,000 yards. Commenced echo ranging to
attract him to us. Apparently this was the wrong
procedure because he immediately presented a 180
degree track, dropped one depth charge, and
disappeared over the horizon.
1431
Surfaced and proceeded to the vicinity of ship
contacts No. 1 and No. 2.
1508
Sighted Ship contacts No. 1, and No. 2.

NOTE:-
The actions of this vessel from this time until
1400, 26 January 1945 is contained in a separate
SECRET report. Made ship contacts No. 7 and 8.
Ships SUNK - one 500 T. Patrol Boat.
Ships DAMAGED - one 500 T. Picket Boat.
(Aircraft Contact No. 1) 1010, 24 January 1945.
APR contact. Verified by SD contact. Range 4 miles.
Submerged. Two aerial Bombs. Not too close.

26 January 1945.

1400
Cruising submerged. Sighted ship. (Ship Contact No.
9). Ship was about 3,000 T. Goal post mast forward
and stack aft. Closest range attained 3,000 yards.
This ship was echo ranging, long scale, on 18 Kcs.
1701
Surfaced. Commenced tracking. Target was steaming
at about 8 knots and his course was erratic. Attempted
to make end arounds but he kept his stern towards us
continually. This was true at ranges up to 20,000
yards. At intervals the target increased speed to 18
knots. Believe this vessel was taking accurate
bearings on our SJ radar. Also believe this ship is
a picket boat with modern equipment.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

27 January 1945.

0525 Lost contact with target. Searched area without
      regaining contact.
0918 Submerged to rest crew.
1806 Surfaced.
2000 Sent contact report and pertinent information on ship
      contact No. 9.
2207 Radar contact 18,000 yards. Commenced tracking. We
      had regained contact with ship contact No. 9. He
      continued to use his same tactics and kept his stern
      to us continually.

28 January 1945.

0100 Sent new contact report on ship contact No. 9.
0110 Set course for SAIPAN.
0751 (Aircraft Contact #2) Sight and SD radar simultaneously.
      Range 8 miles. Submerged.
0855 Surfaced. Proceeded to SAIPAN.

31 January 1945.

      Arrived SAIPAN.

(C) WEATHER:

      During the period 11 January to 19 January enroute BONINS
      area, heavy winds and seas from a general westerly direction were
      encountered which delayed us two (2) days. These conditions
      prevailed during our time in the area and prevented proper use of
      the deck guns.

(D) TIDAL INFORMATION:

      The only current encountered was due to the heavy wind and
      seas. The set was in a general easterly direction drift .5 knots.

(E) NAVIGATIONAL AIDS:

      No remarks.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

                                                                U.S.S. SENNET (SS408)

(F)     SHIP CONTACTS:

NO.     TIME    L.T.            TYPE(S)         INITIAL EST.COURSE HOW CON- REMARKS
        DATE    LONG.                           RANGE   & SPEED    TACTED

1.      1940    30 - 00 N       Picket          7,000   Lying To   SN
        1-20    141 - 00 E

2.      1940    30 - 00 N       Escort for      7,000   Lying To   SN
        1-20    141 - 00 E      Picket

3.      0212    30 - 00 N       Large AO        18,000  340°(T)    R     Attack
        1-21    140 - 50 E                              8 knots          #1 & 2.

4.      0300    30 - 15 N       AM or TB        13,000  340°(T)    R     Attack
        1-21    140 - 40 E                              8 knots          #1 & 2.

5.      0300    30 - 15 N       AM or TB        10,000  340°(T)    R     Attack
        1-21    140 - 40 E                              8 knots          #1 & 2.

6.      0400    30 - 15 N       AM or TB        8,000   340°(T)    R     Attack
        1-21    140 - 30 E                              8 knots          #1 & 2.

7.      1222    30 - 00 N       Small           6,000   Patrolling SN
        1-25    139 - 30 E      Picket

8.      0616    30 - 00 N       Escort for      8,000   Patrolling SD
        1-26    139 - 30 E      Picket

9.      1400    30 - 00 N       Large           18,000  Patrolling P
        1-26    139 - 20 E      Picket

                                                - 5 -

                                                                ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

(G) AIRCRAFT CONTACTS:

CONTACT NUMBER                                | 1           | 2
||
Date                                          | 2-24        | 2-28
S Time (Zone)                                 | 1010        | 0751
U                                             |             |
B Position: Lat.                              | 32 - 10 N   | 27 - 24 N
M                                             |             |
A Long.                                       | 141 - 05 E  | 137 - 00 E
R                                             |             |
I Speed                                       | 17          | 17
N                                             |             |
E. Course                                     | 070         | 180
                                              |             |
Trim                                          | 19 feet     | 19 feet
                                              |             |
Minutes Since Last SD Radar Search            |             |

. Number                                      | 1           | 2
A Type                                        | Search      | Search
I Probable Mission                            | APR & SD    | SD & Sight
R How Contacted                               |             |
C                                             |             |
R Initial Range                               | 4 miles     | 8 miles
A                                             |             |
F Elevation Angle                             |             | 10°
T Range & Relative Bearing of Plane           |             | 110°
  when It Detected S/M.                       |             |

C Sea: (Stat. (Beaufort))                     | 3           | 3
O                                             |             |
N (Direction Rel)                             | 300°        | 0°
D Visibility (Miles)                          | 6 miles     | 12 miles
I                                             |             |
T Clouds: (Height in Ft.)                     | 2,000       | 8,000
I                                             |             |
O (Percent Overcast)                          | 100%        | 50%
N                                             |             |
S Moon: (Bearing (Rel))                       |             |
  (Angle)                                     |             |
  (Percent Illum.)                            |             |

Type of S/M Camouflage on this patrol         | LIGHT GRAY
                                              |
                                  - 6 -
ENCLOSURE (::)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET TORPEDO ATTACK NO. 1 PATROL NO. L

Time Date Lat. Long.
0448 (I) 21 January 1945 30 - 15 N 140 - 30 E
Target Data

DESCRIPTION: Large AO with 3 AN or TB Escorts.

Ship's / Sunk NONE

Ship's / Damaged NONE
or probable sunk

Target Draft Course Speed Range
20 ft. 005 8 1000

OWN SHIP DATA
Speed Course Depth Angle (at firing)
12 240 Surface 0

FIRE CONTROL AND TORPEDO DATA

Type Attack: Night, Surface, Radar.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)
C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

| | 3 | 4 | 5 | 6 |
|---|---|---|---|---|
| Tubes Fired | | | | |
| Track Angle | 68 S | 69 S | 70 S | 75 S |
| Gyro Angle | 012½ | 014 | 015½ | 020 |
| Depth Set | 6 | 6 | 6 | 6 |
| Power | 28 | - | - | - |
| Hit or Miss | Miss | Miss | Miss | Miss |
| Erratic | No | No | No | No |
| Mark Torpedo | 18-1 | 18-1 | 18-1 | 18-1 |
| Serial | 56661 | 56818 | 55773 | 56561 |
| Mark Exploder | 8-5 | 8-5 | 8-5 | 8-5 |
| Serial Number | 10625 | 10812 | 10907 | 10085 |
| Actuation Set | No | No | No | No |
| Mark Warhead | 18-1 | 18-1 | 18-1 | 18-1 |
| Serial Number | 1335 | 3608 | 1726 | 3486 |
| Explosive | Torpex | Torpex | Torpex | Torpex |
| Firing interval | 105 | 105 | 105 | 105 |
| Spread | Divergent | Divergent | Divergent | Divergent |
| Sea Condition | 1-2 | 1-2 | 1-2 | 1-2 |
| Overhaul Activity | Submarine Base, Pearl Harbor, T.H. |

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA (Continued).

U.S.S. SENNET                 TORPEDO ATTACK NO. 2                 PATROL NO. 1

Time                          Date                                 Lat.                 Long.
0804 (I)                      21 January 1945                      30 - 30              140 - 20 E

                                        Target Data

DESCRIPTION: Large AO with 3 TB or AM Escorts.

Ship's / Sunk                 NONE
Ship's / Damaged
or probable sunk              NONE

Target Draft                  Course               Speed                Range
20 ft.                        340                  8                    1,500

                                        OWN SHIP DATA

Speed                         Course               Depth                Angle
5                             140                  Periscope            0

                                        FIRE CONTROL AND TORPEDO DATA

Type Attack: Day, Submerged, Periscope

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

Tubes Fired                                                 1                               2
Track Angle                                                 2 P                             28 P
Gyro Angle                                                  357½                            352 [HANDWRITTEN: 40]
Depth Set                                                   6                               6
Power                                                       28                              28
Hit or Miss                                                 Miss                            Miss
Erratic                                                     No                              No
Mark Torpedo                                                18-1                            18-1
Serial                                                      56699                           55785
Mark Exploder                                               8-5                             8-5
Serial Number                                               11033                           10921
Actuation Set                                               No                              No
Actuation Actual                                            No                              No
Mark Warhead                                                18-1                            18-1
Serial Number                                               1815                            3958
Explosive                                                   Torpex                          Torpex
Firing Interval
Spread                                                      To hit                          To hit
Sea Condition                                               1-2                             1-2
Overhaul Activity                                           Submarine Base, Pearl Harbor, T.H.

                                                            - 10 -

                                                                                                ENCLOSURE (A)

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U.S.S. SENNET (SS408)

(I) MINES:

No evidence of mining was seen during this patrol.

(J) ANTI-SUBMARINE MEASURES AND EVASION TACTICS:

This area is covered by radar equipped search planes. Only two
of these were encountered, one of which dropped two bombs near SENNET.

However there were indications on the APR of several other air-
borne radar sets. All APR contacts were checked by the SD before any
action was taken

No evidence of radar was found during the attacks on the escorted
AO.

There was evidence of a radar detector on the large picket vessel
encountered. He apparently detected our SJ radar and could take bear-
ings on it.

(K) MAJOR DEFECTS AND DAMAGE:

1. Forward Trim Tank.

A large leak in Forward Trim Tank was first noticed by its
effect on the sound gear. The interference started at 100 ft.
Kool depth and increased with depth. A check up showed we were
gaining 600 lbs/hr. at 120 ft.

(L) RADIO:

New whip antennae installed by Submarine Base, Pearl Harbor, T.H.
proved to be most unsatisfactory, except as receiving antennae.
Even as receiving antennae they had but one-third the receptivity of
either contour line antenna. Shear valves in control room leaked
excessively at shallow depths. Our only success in using wing
antennae as receiving antennae was by installing a "jumper" to link
both side antennae together to enable us to transmit on 335 kcs. for
a range approximately of 12 miles. Attempts to use them as
transmitting antennae at greater distance failed.

The new whip antenna installed at Submarine Base, Pearl Harbor,
T.H., worked very satisfactorily as a receiving antenna on Sub Fox
schedules. Not enough information has as yet been gathered to report
on the whip as a transmitting antenna.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(L) RADIO (Continued).

Antenna trunk flooded out on each dive, but a 200 watt lamp was
burned in the trunk while ship was on the surface. This permitted
antennae to be used.

All SubPac Serials were received despite continual radio jamming
by the Japanese. Three transmissions were made despite serious
interruption. This was the result of exceptional
performance by the CRM.

To guard the Fox schedules. The RBS-1 and one of the ship
RAL - 8's were fed into a mixer box at all times. As a result, no
messages were missed while the ship was surfaced.

Jamming was worst by CW particularly in the mother areas. Its
effect was decreased as the ship came southward. Other jamming was
by "bagpipe" "sawtooth" and voice.

(M) RADAR

1. SD-4 Radar

The SD-4 was used going to and from the area and then it
was keyed at two, three, and five minute intervals. When on
station it was used only on occasions. The set gave good
results for reasonably high flying planes but low flying planes
came in as close as four miles before they were picked up.
B-29's and other large bombers were picked up at ranges between
thirty and thirty-five miles. During the patrol we experienced
no trouble what-so-ever in regard to maintenance.

2. SJ-1 Radar

The SJ-1 did not work as satisfactorily as the SD. For
one thing its operation was erratic. It was not until the
patrol was half over that reliable operation and good ranges
were obtained. Then we obtained ranges of 23,000 yards on a
tanker and 70,000 to 80,000 on land contacts.

The first trouble came when the main power switch on the
control unit burned out. This was replaced by a RAL switch,
because no others were available. At the same time the volt
meter in the same unit was found to be reading 50 to 60 volts too
low. This caused an overload on the regulated rectifiers for
all the rectifiers were slightly gassy. All the 5 U 4 G tubes
in the regulated rectifiers and the 836 tube in the H.V.
rectifier were replaced. During the patrol, the ringing time
of the echo box dropped appreciably. Replacing 6 AC 7 tubes

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(M) RADAR: (Continued).
     2. SJ-1 Radar Continued.
          In the IF strip and magnetions helped temporarily. The TR tube
          was checked and found all right. But when it was replaced, the
          set worked satisfactorily from then on. Other minor casualties
          were erratic function of the frequency meter in the 60 AIM a
          short in aJones plug, and a jump in the range step. The
          frequency meter was replaced by a new one. Jones plug was
          renewed and range unit was readjusted. Also on several
          occasions 5 U 4 G tubes in both regulatr rectifiers became
          gassy and had to be replaced.

          During the patrol the SJ was kept continuously warmed up and
          used only at night.

     3. ST Radar
          On our first submerged attack no ranges were obtained on
          the ST radar and this put us at a very big disadvantage. But
          after making small adjustments in the transmitter, the ST gave
          us very good results. On the second submerged attack ( 26
          January 1945) ranges up to 12,000 yards were obtained on large
          picket ships at a depth of 55 feet. No other trouble was
          encountered with this radar.

(N) SOUND GEAR AND SOUND CONDITIONS:
     The greatest range received on sound equipment was upon
     an engine - aft. patrol boat. This contact was made on the JP
     gear. The target had first been sighted visually. This contact
     was pinging with sound gear set at 10 kcs.

     No casualties to sound equipment were suffered. Ship's
     noises were strong on both JP and supersonic gear, particularly
     air sounds caused by a leak in forward trim tank.

(O) DENSITY LAYERS:
     No density layers were encountered. Several BT cards showed
     isothermal layers to 500 feet.

(P) HEALTH, FOOD AND HABITABILITY:
     Health of the crew was excellent. Food serving and preparation
     were excellent.

- 13 -
ENCLOSURE (A)

— page 20 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

(Q) PERSONNEL:
The performance of all personnel was excellent. We carried
78 men and 11 officers (one PCO) and the problem of lookouts and
watch was simple.

(R) MILES STEAMED - FUEL USED:
MIDWAY to area 2,140 miles 27,000 gallons
In area 1,320 miles 25,270 gallons
Area to SAIPAN 1,230 miles 16,000 gallons

(S) DURATION:
Days enroute to area 14
Days in area 8
Days enroute to base 4
Days submerged 6

(T) FACTORS OF ENDURANCE REMAINING:
Torpedos Fuel Provisions Personnel Factor
0 52,000 gal. 40 days Indefinite
Limiting factors this patrol - Operation Order and Torpedoes.

(U) RADIO AND RADAR COUNTERMEASURES:
The APR search receiver was manned continuously day and night
in the area. It gave very satisfactory results, and there were no
equipment failures during the patrol. When a contact was made
which was believed to be an aircraft radar, the SD was turned on
and keyed every minute to determine the range of the aircraft.
Once an aircraft radar was picked up on the APR and after the SD
had been keyed for a period of 5 - 10 minutes at minute intervals,
the contact on the APR was lost (due to radar being turned off).
After 5 minutes contact was made on SD at 4 miles. We dived and
contact was verified by two bombs exploding above us when we
reached 150 feet. It is believed that the aircraft detected our
SD, the pilot realized he no longer needed his own radar for it
was possible to home on our SD and come in undetected until 4
miles out by flying under our antenna pattern. Land based radar
of 147 mc was picked up off Tori Shima when we were off the south
west end of the island. Although we were in an area where there
were many radar patrol boats, only once was a contact made on
the APR. The contact was on 123 mc and it was maintained for
over three hours.

- 14 -
ENCLOSURE (A)

— page 21 —
U.S.S. SENNET (SS408)
C-O-N-F-I-D-E-N-T-I-A-L

(U) RADIO AND RADAR COUNTERMEASURES (Continued).

During the entire period at no time was a contact made on the
TN-3 unit.

APR CONTACTS
DATE     POSIT      FREQ. PRF. PW     TYPE        REMARKS
TIME     OF SHIP    MC    CPS  USEC.
1-24-45  32-05 N    500   5    Aircraft  Radar was keyed every
0800     140-21 E 152                  1-2 mins. for 20-30 sec.
1-24-45  32-17 N    1000  5    Aircraft  Pulse was flat topped
1000     141-06 E 153                  radar was not keyed
1-25-45  30-06 N    1500  2-4  Aircraft
0450     140-20 E 150
1-25-45  30-00 N    500   12   Land base Antenna was rotated every
0725     140-06 E 147                  2-3 minutes. Radar was
                                       based at Tori Shima and
                                       contact was kept for 2 hrs.
-            Possibly an AS radar with
                                       a directional antenna
                                       coming from a radar patrol
                                       boat. The contact was strong
                                       with irregular pulse shape.
1-25-45  30-26 N    1260  8-12 Ship borne
2300     140-55 E 123
1-26-45  30-03 N    100   10   Unknown   Contact was strong but
1715     140-17 E 183                  doubtful.
                                       Same as fifth contact
1-26-45  -----      1260  8-12 Ship borne
0300     123
1-28-45  29-15N     200-300 2-4  Ship borne  Patrol vessel was nearby
0005     137-10 E 220                  at time of contact but
                                       contact was weak so it
                                       might have been a harmonic
-
1-28-45  25-15 N    750   5    Unknown
1430     137-07 E 230
1-30-45             60    10             SD radar from nearby
1730     116                           submarine
1-31-45  15-30 N    60    5              SC or SK unit from
0430     144-15 E 225                  some island

(V) REMARKS:
    None

- 15 -

ENCLOSURE (A)

— page 22 —
COMMANDER TASK GROUP 17.7
Se
Care of Fleet Post Office,
San Francisco, California,
11 February 1945.

CTG-17.7/A16-3
Serial 06
C-O-N-F-I-D-E-N-T-I-A-L
FIRST ENDORSEMENT to
U.S.S. SENNET, Report
of War Patrol No. 1.

From: The Commander Task Group 17.7.
To : The Commander in Chief, U.S. Fleet.
Via : The Commander Submarine Force, Pacific Fleet.
The Commander in Chief, U.S. Pacific Fleet.

Subject: U.S.S. SENNET (SS408) - Report of First War Patrol.

1. The first war patrol of the U.S.S. SENNET was spent
in the area immediately north of the BONIN ISLANDS. The mission
was of a special nature, only six torpedoes being carried.
Coverage of the assigned area was good within the limitations
imposed by weather and expenditure of torpedoes. Eight days
were spent in the area seeking out the enemy and all torpedoes
were fired.

2. Two contacts worthy of torpedo fire were made. Of
these only one could be closed. This was a single large tanker
whose vicinity was amply sprinkled with escorts. The efforts of
the enemy to protect his shipping is well illustrated by the
ratio in this convoy - three to one. Two unsuccessful attacks
were made on this tanker, all torpedoes carried being fired at
her. A summary of the attacks follows:

TORPEDO ATTACK #1. Two and one quarter hours were
spent developing a solution of the tankers track. This should
have been ample and was so considered by the Commanding Officer.
A night surface attack was begun, Captain Porter aggressively
closing his prey and firing four torpedoes on a 70 starboard
track, range 1400 - 1600 yards. Conditions appeared ideal for
further donation to Davy Jones but unfortunately all torpedoes
missed. No known reason can be attributed for this.

TORPEDO ATTACK #2. The approach of dawn preventing
another surface attack, SENNET flanked the group and submerged
ahead for a daylight attack with two remaining torpedoes. It
is noted that the course of the target on this attack was the
same as the base course obtained by the solution of the problem
and that the enemy apparently remained unalerted. Two torpedoes
were fired, again under what appeared to be an ideal set up.
Again the attack was unsuccessful and no reason for the misses
is apparent.

3. In this particular instance the enemy refrained from
the customary dawn radical change of base course. He apparently

- 1 -

— page 23 —
CONFIDENTIAL
Serial 06
Subject: U.S.S. SENNET (SS408) - Report of First War Patrol.
                                                                11 February 1945.

wanted to get this tanker to its destination in a hurry. The
lack of aggression on the part of three escorts is noted with
pleasure and is a possible indication that substitutes are being
used on the Nip Team.

                                4.
        In latter attacks one 500 ton picket boat was sunk
and one damaged.

                                5.
        The actions of the 3,000 ton ship sighted on 26
January definitely appears to be suspicious. If the vessel is
a picket ship it is certainly an expensive one. At times this
ship is reported to have made 18 knots. Just what the enemy's
intention could have been is constantly presenting his stern is
not known. Possibly the vessel has torpedo tubes, inviting
visiting firemen to close him for a shot.

                                6.
        The intelligent use of the APR and SD equipment is
noted with satisfaction.

                                7.
        The Group Commander congratulates the Commanding
Officer, Officers and Crew of the SENNET on the completion of
this patrol, so ably conducted. While contacts were unfortunately
few and attacks with torpedoes unsuccessful, much useful infor-
mation was obtained as a result. This information is contained
in a special report. The SENNET returned from patrol in a clean
ship-shape condition, was in sound material condition, and a credit
to her Commanding Officer. All defects will be remedied during
a short stay in SAIPAN prior to her next patrol.

                                                                [SIGNATURE: G. E. Peterson]
                                                                G. E. PETERSON.

— page 24 —
FF12-10(A)/A16-3(18) SUBMARINE FORCE, PACIFIC FLEET 1d [HANDWRITTEN: (mark)]
[HANDWRITTEN: 2ND Copy]
Serial: 0314

CONFIDENTIAL

SECOND ENDORSEMENT to
SENNET Report of
First War Patrol

Care of Fleet Post Office,
San Francisco, California,
22 February 1945

COMSUBSPAC PATROL REPORT NO. 673
U.S.S. SENNET - FIRST WAR PATROL.

NOTE: THIS REPORT WILL BE
DESTROYED PRIOR TO
ENTERING PATROL AREA.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander-in-Chief, United States Fleet.
Via : The Commander-in-Chief, U. S. Pacific Fleet.

Subject: U.S.S. SENNET (SS408) - Report of First War Patrol
(5 January to 31 January 1945).

1. The first war patrol of the SENNET, under the command
of Commander G. E. Porter, U. S. Navy, was conducted in the Bonins
Islands area. Additional information concerning this patrol is con-
tained in a separate report of higher security classification.

2. The SENNET made two aggressive torpedo attacks on a
heavily escorted single large tanker. Unfortunately no hits were ob-
tained in either of these attacks, her only opportunity for torpedo
attack. The special assignment, the subject of a separate report, was
conducted in a most commendable manner.

3. Award of Submarine Combat Insignia for this patrol is
authorized.

4. The Commander Submarine Force, Pacific Fleet, congratu-
lates the commanding officer, officers, and crew of the SENNET for an
aggressive, successful first patrol.

[STAMP: Office of FLEET MAINTENANCE
MAR 0 1945
RECEIVED
NAVY DEPARTMENT] MERRILL COMSTOCK,
Chief of Staff.

[STAMP: RECEIVED J-C FILES
Room 2055
By 15 MAR 1945
By File No (86) ALL-3(18) / 157862
Copy No. [HANDWRITTEN: 2 of 5]]

Distribution and authentication
on following page

- 1 -

99

— page 26 —
[HANDWRITTEN: O] [HANDWRITTEN: D] [HANDWRITTEN: O]
PROCESSED COPY

U. S. S. SENNET (SS408)

In reply refer to:
SS408/A16-3
Serial: 0001-45
[STAMP: DECLASSIFIED]
[TYPED, CROSSED OUT: T-O-P S-E-C-R-E-T]
From:
To:
Via:
Subject:
Reference:
Enclosure:
Care of Fleet Post Office,
San Francisco, California,
[TYPED, FADED: CONFIDENTIAL - DOD DIR 5200.9]
[HANDWRITTEN: BY J. Kues DATE 4-16-60]
31 January 1945.

The Commanding Officer.
The Commander-in-Chief, U. S. Fleet.
(1) The Commander Submarine Division
(2) The Commander Submarine Squadron
(3) The Commander Submarine Force, Pacific Fleet.
(4) The Commander-in-Chief, U. S. Pacific Fleet.

U.S.S. SENNET - Supplement to Report of War Patrol
Number ONE.

(a) Commander Submarine Force, Pacific Fleet
Memorandum S75/(3) of 30 December 1944.

(A) Subject Report.

1. In accordance with reference (a), Enclosure (A) covering
the activities of this vessel during the period from 0800 (I), 21
January 1945 to 1400 (I), 26 January 1945, is forwarded herewith.

/s/ G. E. PORTER.

3 59

— page 27 —
T-O-R S-E-C-R-E-T
U.S.S. SENNET (SS408)

Ten (10) attacks were made on enemy vessels with the Mark 27
Torpedo, during the period 0800 (I), 21 January 1945, to 1400 (I),
26 January 1945. The following data is submitted concerning these
attacks:

TORPEDO ATTACK No. 1.

0804 (I), 21 January 1945 Lat. 30-00 W Long. 141-00 E.

DESCRIPTION

One large Tanker escorted by three (3) Chidori or mine sweeper type
escorts.

Ship's Sunk                               - NONE

Ship's Damaged                            - NONE

Target Draft                              Course             Speed             Range
16 Feet                                   340°T.             8 knots           700 yards

OWN SHIP'S DATA

Speed                                     Course             Depth             Angle
2.5 knots                                 160°T.             150 feet          1° Down

ATTACK DATA

Tube Fired                                7

Mark Torpedo                              27

Serial No.                                622

Sea Conditions                            Force 1 to 2

Sound Conditions                          Excellent, Isothermal layer
                                          to 500 feet.

Depth of Water                            2000 fathoms

Target Turn Count                         Not taken

Distance to nearest Land or Reef          12 Miles

Target Bearing at firing instant          This Torpedo was fired 700 yards
                                          dead ahead of one escort vessel
                                          and about 300 yards from the
                                          track of the Tanker.

- 1 -

ENCLOSURE (A)                             3 59

— page 28 —
U.S.S. SENNET (SS408)

T-O-P S-E-C-R-E-T

TORPEDO ATTACK No. 2.

1656 (I), 21 January 1945 Lat. 30-00 W Long. 141-00 E

DESCRIPTION

One large Patrol Boat approximately 500 tons.

Ship's Sunk - NONE

Ship's Damaged - NONE

Target Draft Course Speed Range
4-5 feet 255°T 6 knots 500 yards

OWN SHIP'S DATA

Speed Course Depth Angle
2.5 knots 075°T. 150 feet 0°

ATTACK DATA

Tube Fired 9
Mark Torpedo 27
Serial No. 767
Sea Conditions Force 1 to 2
Sound Conditions Excellent, Isothermal layer to
500 feet.
Depth of Water 2000 fathoms
Target Turn Count Not Taken
Distance to nearest shore or reef 40 Miles
Target Bearing at firing instant Target was dead ahead of us
heading toward us.

- 2 -

ENCLOSURE (A)

— page 29 —
T-O-P S-E-C-R-E-T
U.S.S. SENNET (SS408)

TORPEDO ATTACK No. 3.

0752 (I), 22 January 1945 Lat. 30-00 W. Long. 141-00 E.

DESCRIPTION
One Large Patrol Boat approximately 500 Tons.
Ship's Sunk - NONE
Ship's Damaged - NONE

Target Draft | Course | Speed | Range
4-5 feet | 290°T. | 6 knots | 400 yards.

OWN SHIP'S DATA
Speed | Course | Depth | Angle
2.5 knots | 095°T. | 165 feet | 2° down

ATTACK DATA
Tube Fired | 7
Mark Torpedo | 27
Serial No. | 427
Sea Conditions | Force 1 to 2
Sound Conditions | Excellent
Depth of Water | 2000 fathoms
Target Turn Count | Not Taken
Distance to nearest shore or reef | 40 Miles
Target Bearing at firing instant | 015° Rel.
Target heading toward us and
passed close aboard our stern-
Sound intensity on JP sound gear
was very high.

- 3 -

ENCLOSURE (A)

— page 30 —
T-O-P S-E-C-R-E-T U.S.S. SENNET (SS408)

TORPEDO ATTACK No. 4.

0830 (I), 23 January 1945 Lat. 30-00 N. Long. 141-00 E.

DESCRIPTION

One large Petrol Boat approximately 500 Tons.

Ship's Sunk - NONE
Ship's Damaged - NONE

Target Draft Course Speed Range
4-5 feet 115°T. 6 knots 500 yards.

OWN SHIP'S DATA

Speed Course Depth Angle
2.5 knots 295°T. 160 feet 0°

ATTACK DATA

Tube Fired 7
Mark Torpedo 27
Serial No. 765
Sea Conditions Force 3
Sound Conditions Good
Depth of Water 2000 fathoms
Target Turn Count 240 Turns
Distance to nearest shore or reef 40 Miles
Target Bearing at firing instant Dead ahead heading toward us.

- 4 -

ENCLOSURE (A)

— page 31 —
U.S.S. SENNET (SS408)

T-O-P S-E-C-R-E-T
TORPEDO ATTACK No. 5.
0842 (I), 23 January 1945 Lat. 30-00 W Long. 141-00 E.

DESCRIPTION
One large Patrol Boat approximately 500 Tons.
Ship's Sunk - NONE
Ship's Damaged - NONE
Target Draft                                Course             Speed             Range
4-5 feet                                   115° T.            6 knots           100 yards

OWN SHIP'S DATA
Speed                                      Course             Depth             Angle
2.5 knots                                  323° T.            170 feet          1° down

ATTACK DATA
Tube Fired                                 8
Mark Torpedo                               27
Serial No.                                 314
Sea Conditions                             Force 3
Sound Conditions                           Good
Depth of Water                             2000 fathoms
Target Turn Count                          240 Turns
Distance to nearest land or reef           40 Miles
Target bearing at firing instant           Dead ahead passed directly over
                                           head. Sound intensity very high.

- 5 -

ENCLOSURE (A)

— page 32 —
U. S. S. SENNET (SS408)

T-O-P S-E-C-R-E-T
TORPEDO ATTACK No. 6.

1146 (I). 23 January 1945 Lat. 30-00 W. Long. 141-00 E.

DESCRIPTION

One large Patrol Boat approximately 500 Tons.

Ship's Sunk - One (1) 500 Tons Patrol Boat. Torpedo hit 2 minutes
30 seconds after firing. Sighted second patrol boat
picking survivors up 50 minutes after torpedo hit.

Ship's Damaged - NONE

Target Draft Course Speed Range
4-5 feet Unknown 6 knots Approximately
300 yards.

OWN SHIP'S DATA

Speed Course Depth Angle
2.5 knots 200°T. 155 feet 0°

ATTACK DATA

Tube Fired 9
Mark Torpedo 27
Serial No. 435
Sea Conditions Force 3
Sound Conditions Good
Depth of Water 2000 fathoms
Target Turn Count Not Taken
Distance to nearest land or reef 40 Miles
Target bearing at firing instant We were circling under neath two
(2) patrol boats when he started
his screws. Sound intensity was
high.

- 6 -

ENCLOSURE (A)

— page 33 —
T-O-P S-E-C-R-E-T
U. S. S. SENNET (SS408)

TORPEDO ATTACK No. 7, 8, and 9.
1148 (I), 23 January 1945 Lat. 30-00 W Long. 141-00 E.

DESCRIPTION
One large Patrol Boat approximately 500 Tons.
Ship's Sunk - NONE
Ship's Damaged - NONE

Target Draft
4-5 feet

Course        Speed        Range
Unknown       6 knots      Approximately
                           100 yards.

OWN SHIP'S DATA
Speed        Course        Depth        Angle
2.5 knots    215° T.       160 feet     0°

ATTACK DATA
Tubes Fired                10           7            8
Mark Torpedo               27           27           27
Serial No.                 336          441          630
Sea Conditions             Force 3
Sound Conditions           Good
Depth of Water             2000 fathoms
Target Turn Count          Unknown
Distance to nearest land or reef 40 Miles
Target bearing at firing instant We were circling underneath this
                                 patrol boat as he maneuvered to
                                 rescue survivors from patrol boat
                                 sunk in attack No. 6. In all
                                 three (3) instances the sound in-
                                 tensity was very high and his bear-
                                 ing change rate showed him to be
                                 close aboard.

- 7 -
ENCLOSURE (A)
[HANDWRITTEN: 3 59]

— page 34 —
U. S. SENNET (SS408)
T-O-P S-E-C-R-E-T

TORPEDO ATTACK No. 10.

1035 (I), 26 January 1945 Lat. 30-00 W Long. 141-00 E.

DESCRIPTION

One large Patrol Boat approximately 500 Tons.

Ship's Sunk - NONE
Ship's Damaged - NONE

Target Draft Course Speed Range
4-5 feet Unknown 6 knots Dead
Overhead

OWN SHIP'S DATA

Speed Course Depth Angle
2.5 knots 220°T. 155 feet 0°

ATTACK DATA

Tube Fired 11
Mark Torpedo 27
Serial No. 763
Sea Conditions Force 1 to 2
Sound Conditions Excellent
Depth of Water 2000 fathoms
Target Turn Count Unknown
Distance to nearest land or reef 50 miles
Target bearing at firing instant We were circling underneath target
when he got underway, his screws
were first detected through the hull.
The sound intensity was extremely
high on the JP sound gear. Of the
ten (10) Mark 27 torpedoes fired this
was undoubtedly the best firing positio
attained by this vessel.

- 8 -

ENCLOSURE (A)

— page 35 —
T-O-P S-E-C-R-E-T
U. S. S. SENNET (SS408)

GUN ATTACK No. 1.
PATROL No. 1.
1757 (I), 23 January 1945 Lat. 30-25 W Long. 141-05 E.

DESCRIPTION

One large Patrol Boat approximately 500 Tons.

Ship's Sunk - NONE

Ship's Damaged - One (1) 500 Ton Patrol Boat. Saw two (2) 5" - 25"
or probable sunk cal. hit.

DETAILS OF ACTION

This is undoubtedly the worst exhibition of a gun
action that I have ever observed. The following set of circumstances
produced this fiasco:

1. The SJ Radar picked this opportunity to cease functioning.

2. A force 4 sea limited ship's maneuverability. We had to keep the sea
20 degrees either side of dead astern so that the guns could be manned.
Therefore the range could not be decreased sufficiently.

3. The trainers sight was flooded out. The binoculars used as replace-
ment went out on the first salvo. This information was not relayed
to control in the conning tower and as a result the spotting in
deflection was completely erroneous.

4. The mark 32 ammunition produced at least 50 percent prematures close
aboard. This was more disconcerting than the gun fire returned by
the enemy.

5. There was one amusing incident connected with this firing. The trainer
on the forward gun (his sights out) was taking quite a verbal lacing
from the captain. The hot shells being ejected from the gun bounced
off the life line and repeatedly hit the trainer in the stern sheets.
During the entire firing the trainer was convinced that the gun
captain was using some persuasion to improve his training ability.

6. Approaching darkness discontinued the action before the defects could
be remedied and contact with the target was lost due to the Radar being
out of commission.

- 9 -

ENCLOSURE (A)

3 59

— page 36 —
COMMANDER TASK GROUP SEVENTEEN POINT SEVEN

CTG-17.7/A16-3/jhg
Serial: 004
TOP SECRET

c/o Fleet Post Office,
San Francisco, California.
11 February 1945.

FIRST ENDORSEMENT to
U.S.S. SENNET Top Secret
ltr. 0001-45 of 1/31/45

From: Commander Task Group SEVENTEEN POINT SEVEN.
To : Commander-in-Chief, U.S. FLEET.
Via : (1) Commander Submarine Force, PACIFIC FLEET.
      (2) Commander-in-Chief, U.S. PACIFIC FLEET.

Subject: U.S.S. SENNET - Supplement to Report of War Patrol
          Number ONE.

1. Subject report covers activities of the SENNET during her
First War Patrol. Eight attacks were made on picket vessels or escorts,
using one Mark 27 torpedo on each with the exception of attack seven when
three were fired, slow fire. The cause for so many misses is not readily
apparent to this command. Conversation with the Commanding Officer and
with personnel experienced in this weapon establishes the possibility that
torpedoes were under running targets. This possibility is being investigated.
Mal-adjustment of depth setting spring pressures is suspected.

2. The Commanding Officer feels that the one hit obtained on one
five hundred ton patrol boat was the result of heavy weather breaching or
nearly breaching the torpedo.

3. SENNET was forced to accept the weather as a partner of the
enemy in her gun battle of January 23rd. In connection with the large
percentage of prematures with Mark 32 fused ammunition the only reason that
can be attributed is bad shooting. With the vessel rolling in a heavy sea
and shooting wildly, if shots are fired on the down side of the roll,
proximity fused ammunition would undoubtedly premature. Normally, it is
understood, about 30% of Mark 32 fused ammunition will premature. The
increase, to use the words of the report, to "at least 50 percent" would
undoubtedly be due to the ammunition going off close as it passed over a
crest, if fired on the down roll or near the bottom of a down roll.

4. Despite the negative nature of this patrol Captain Porter
brought home valuable information concerning the service use of both Mark
27 Torpedoes and Mark 32 fused ammunition. As a result, it is confidentially
expected that adjustments to the former will cause them to more effectively
do their job at a later and more important time.

5. It is recommended that further tests in a rough sea, from
a low gun platform be conducted with proximity fused ammunition.

- 1 -
[STAMP: 3 59]

— page 37 —
COMA R TASK GROUP SEVENTEEN POINT S. N

CTG-17.7/A16-3/jhg
Serial: 004

TOP SECRET

Subject: U.S.S. SENNET - Supplement to Report of War Patrol
          Number One.

          c/o Fleet Post Office,
          San Francisco, California.
          11 February 1945.

6. The Group Commander congratulates the Commanding
Officer, Officers and Crew of the SENNET on their damage to the
enemy, their contribution to our knowledge of special weapons under
service conditions and recommends the following be credited.

SUNK (EC) Large Patrol Trawler (SMC) 500 Tons
DAMAGED (EC) ..... Large Patrol Trawler (SMC) 500 Tons

GRAND TOTAL 1000 Tons

Sunk and Damaged

....... /s/ G. E. PETERSON.

— page 38 —
FF12-10/A16-3
Serial 0009

[STAMP: S. No. QM42-7-45A]
[HANDWRITTEN: Ga] [HANDWRITTEN: 3 59]
[STAMP: R.S. No. ]

SUBMARINE FORCE, PACIFIC FLEET
Care of Fleet Post Office,
San Francisco, California.

February 24, 1945

[STAMP: SECRET]
SECOND ENDORSEMENT to
USS SENNET Top Secret
ltr. file SS408/A16-3
Serial 0001-45 of 31
January 1945.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander in Chief, U. S. Fleet.

Subject: U.S.S. SENNET Supplement to Report of War
Patrol Number ONE -- Mark 27 torpedoes and
Mark 32 fused ammunition firings.

1. The first war patrol of the SENNET, under the
command of Commander G. E. Porter, U.S. Navy, was conducted
in the Bonins Islands Area. This information supplements
previous confidential report of war patrol number ONE.

2. The Commander Submarine Force, Pacific Fleet,
congratulates the commanding officer, officers, and crew of
the SENNET on their damage to the enemy and their fine efforts
in connection with these new weapons. The SENNET is credited
with having inflicted the following damage upon the enemy
during this patrol:

[STAMP: COMMANDER IN CHIEF
U.S. FLEET OFFICE
RECEIVED
1945 MAR 11 00]

S U N K
1 SMC (Large Patrol Trawler) (EC) - 500 tons (Attack No. 6)

D A M A G E D
1 SIC (Large Patrol Trawler) (EC) - 500 tons (Gun Attack No. 1)

MERRILL COMSTOCK,
Chief of Staff.

DISTRIBUTION:

Cominch (2)
CNO (2)
Cincpac (2)
ComSubpac (2)
Comsubpacdcon (2)
Comsubtrainpac (2)

[SIGNATURE: E. L. Hynes]
E. L. HYNES, 2nd,
Flag Secretary.

Comsubslat (2)
Comsubs7thfleet (2)
All Squadron Commanders (1)
All Division Commanders (1)
C.O. Submarines, Pacific
(1 copy this endorsement only)

[STAMP: SECRET] [HANDWRITTEN: 3 59]

— page 39 —
SS408/A16-3
Serial: 04-45
C-O-N-F-I-D-E-N-T-I-A-L
[STAMP: DECLASSIFIED]

From:
To:
Via:

Subject:
Enclosure:

1.
vessel conducted in the area off KII SUIDO during the period from 7
February 1945 to 9 March 1945, is forwarded herewith.

[HANDWRITTEN: FILMED]
[HANDWRITTEN: 112847] U.S.S. SENNET (SS408)

Care of Fleet Post Office,
San Francisco, California.

[STAMP: DECLASSIFIED NND 760014]
BY [HANDWRITTEN: OPN978K] DATE [HANDWRITTEN: 9/16/77]

The Commanding Officer.
The Commander-in-Chief, U. S. Fleet.
(1) The Commander Submarine Division 281.
(2) The Commander Submarine Squadron 28.
(3) The Commander Submarine Force, Pacific Fleet.
(4) The Commander-in-Chief, U. S. Pacific Fleet.

U.S.S. SENNET - Report of War Patrol Number TWO.

(A) Subject Report.

Enclosure (A), covering the Second War Patrol of this

G. E. PORTER.

— page 40 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(A) PROLOGUE:

Arrived SAIPAN on 31 January 1945. Refit accomplished by U.S.S.
FULTON, under th direction of Commander Submarine Squadron EIGHT.

One day of training in gunnery exercises was held on 5 February
1945.

Dry docked 7 February 1945 to repair leak in Forward Trim Tank.

During the refit period the following transfers were effected:

DETACHED: Commander, D. R. CONNOLLY, U.S. Navy, P.C.O.

Lieutenant, S(05), W. S. SKASE, U.S.N.R.

REPORTED: Torpedoman, J. M. GETTLE, U.S. Navy.

TRANSFERRED: Four (4) Enlisted Men.

RECEIVED: Four (4) Enlisted Men.

The following officers are on board:

NAME                               | PREVIOUS WAR PATROLS
Comdr., George E. PORTER, Jr.,     | THREE (3) BLUEFISH
                                   | THREE (3) GREENLING
                                   | ONE (1) SENNET
Lt-Cdr., Charles R. CLARK, Jr.,    | TWO (2) DACE
                                   | ONE (1) SENNET
Lieut., James D. ROCHE             | ONE (1) BLUEFISH
                                   | ONE (1) SENNET
Lieut., Frank A. ANDREWS,          | ONE (1) SENNET
Lt.(jg), "C" "B" KOSSERT,          | FOUR (4) GREENLING
                                   | ONE (1) SENNET
Ensign, Vesper E. BURKS,           | TWELVE (12) THRESHER
                                   | ONE (1) SENNET
Ensign, John H. VAN NESS,          | ONE (1) SENNET
Ensign, Donnell H. WAGNER,         | ONE (1) SENNET

- 1 -

ENCLOSURE (A)

— page 41 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(A) PROLOGUE Continued:

     Ensign, Elmer V. ANDERSON                               FIVE (5) BLUEFISH
                                                              ONE (1) SENNET

     Torpedoman, James M. GETTLE                              EIGHT (8) S-18

          The following CPO's are on board during this patrol:

     NAME                                  RATE               PREVIOUS WAR PATROLS

     BIRCHARD, Mervale B.,                 CGM(PA)            FOUR (4) GREENLING
                                                              ONE (1) SENNET

     EPLER, George W.,                     CSM(PA)            THREE (3) CUTTLEFISH
                                                              ONE (1) SENNET

     GOLLADAY, Elmer C.,                   CRM(PA)            ONE (1) SENNET

     KARETNUK, Anthony (n),                CMOMM(PA)          NINE (9) SWORDFISH
                                                              ONE (1) SENNET

     HALL, Leon W.,                        CMOMM(T)           FOUR (4) S-45
                                                              ONE (1) SENNET

     BRENGELMAN, Henry B.,                 CEM(PA)            EIGHT (8) SEAWOLF
                                                              ONE (1) SARGO
                                                              ONE (1) SENNET

     DAWSON, Ralph O.,                     CPhM(PA)           FIVE (5) GREENLING
                                                              ONE (1) SENNET

     COGHILL, Kettig S.,                   CMOMM(AA)          ONE (1) BALAO

(B) NARRATIVE:

     Underway for patrol area in accordance with Commander Task Force
     Seventeen Operation Order No. 36-45 of 6 February 1945.

     7 February 1945. (All times will be KING unless otherwise specified).

     1742 (K) Departed SAIPAN as a member of a coordinated attack
                  group in company with U.S.S. LAGARTO and U.S.S. HADDOCK.

                  Commander F. D. LATTA, U.S. Navy, in charge of attack
                  group.
                                   - 2 -
                                                            ENCLOSURE (A)

— page 42 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

8 February 1945.
1200 Position: Lat. 16-35 N. Long. 142 - 30 E.
Routine training unroute area.

9 February 1945.
1200 Position: Lat. 19 - 21 N Long. 139 - 26.5 E.
Routine training unroute area.

10 February 1945.
1200 Position: Lat. 26 - 18 N Long. 137 - 36 E.
Routine training unroute area.

11 February 1945.
1200 Position: Lat. 30 - 24 N Long. 139 - 26 E.
In area searching for Picket Boats.

12 February 1945.
1200 Position: Lat. 29 - 48 N Long. 139 - 26 E.
In area searching for Picket Boats.
0915 SD contact 10 miles.
0916 Submerged.
0925 Surfaced.
1707 SD contact 18 miles.
1710 Submerged.
1718 Surfaced.
1719 SD contact 8 miles. Submerged. Sighted B-29 with periscope.
1721 Surfaced.

13 February 1945.
1200 Position: Lat. 29 - 48 N Long. 136 - 04 E.
0146 SJ contact 034°T. distance 10,800 yards. Contact was on
two (2) Picket Boats. (Ship contacts # 1 and 2.)
Maneuvered under orders of Pack Commander to secure favorable
position for daylight gun attack.
0656 Manned battle surface stations.
0702 Headed for targets, course 130°T. at 17 knots. In line of
bearing. LAGARTO in center SENNET on left flank HADDOCK on
right flank.
0735 Range to target 6,500 yds., formation changed course to 170°T.
and following first salvo of U.S.S. LAGARTO, opened fired at
nearest and left hand Picket Boat. (Picket Boat #1).

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

0750 Shiftd fire to Picket Boat #2. Picket Boat #1, had turned
     away.
0756 Picket Boat #2 caught on fire. Commenced hot pursuit of
     Picket Boat #1.
0801 Commenced firing at Picket Boat #1.
0803 Picket Boat #1 caught on fire.
0820 Sank Picket Boat #1 at point blank range.
     During this engagement a total of 214 rounds of 5 inch 21 cal.
     and 384 rounds of 40 MM ammunitions were expended. Observed
     twenty (20) 5 inch hits in Picket Boat #1 and seven (7) hits
     in Picket Boat #2.
0846 Secured from battle stations surface and resumed scouting
     formation with U.S.S. LAGARTO and U.S.S. HADDOCK.
1223 APR contact 146 M.cs.
1225 Sighted plane bearing 105°T. Distance 5 miles. Submerged.
1233 Heard total of four (4) distant explosions.
1337 Surfaced.
1347 SJ contact on aircraft, bearing 091°T. Distance 31,500 yds.
1403 Contact closed to 14,400 yds. Submerged.
1511 Surfaced.
1935 Picked up radar interference bearing 242°T.
1940 Contacted LAGARTO.
2339 Contacted HADDOCK who had found two (2) more Picket Boats.
     (Ship contacts #3 and #4). U.S.S. HADDOCK remained in
     vicinity of Picket Boats awaiting daylight to submerge for
     torpedo attack. This vessel and U.S.S. LAGARTO opened out to
     westerward to await dawn to make daylight gun attack.

14 February 1945. 1200 Position: Lat. 30 - 00 N. Long. 135 - 13 E.

0652 Manned battle surface stations. Headed for targets, course
     100°T., speed 17 knots. In line of bearing, U.S.S. LAGARTO
     to the south.
0749 Range to targets 5,000 yds. commenced firing at Picket Boats.
     Expended ten (10) rounds of 5 inch 25 cal ammunition at
     Picket Boat #1, and thirty-one (31) rounds of 44 MM ammunition at Picket Boat #2.
     Expended 325 rounds of 44 MM ammunition at both targets. Saw
     one (1) 5 inch hit in target #1 and two (2) 5 inch hits in
     target #2. 40 MM fire appeared to be good especially at closest
     range of 1,800 yds. Received at least two (2) hits on this
     vessel by enemy gunfire, probably 50 cal. One (1) man wounded
     in the back by shrapnel. Enemy 37 MM and 50 cal. fire was
     extremely accurate. The action was terminated due to
     expenditure of 5 inch ammunition.
0817 Fell in astern of the U.S.S. LAGARTO and cleared area.

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U.S.S. SENNET (SS408)

0820 U.S.S. HADDOCK surfaced and joined formation.
0859 Released by attack Group Commander. Proceeded to assigned
patrol area off KII SUIDO.
0901 Submerged.
1555 Surfaced.

15 February 1945. 1200 Position: Lat. 33 - 05.5 N Long. 133 - 43.5 E.

0555 SJ contact on land bearing 305°T., distance 60,000 yds.
0656 SJ radar out of commission.
0707 Submerged.
0736 Sighted land through periscope.
Made close in sweep of Bay between SHIZURI SAKI and MUROTO
ZAKI.
2001 Surfaced. APR contact on land base radar MUROTO SAKI.
SJ contact land bearing 000°T., distance 24,000 yards.
Sent weather report. (SENNET #1).
Decided to patrol traffic route between KII SUIDO and IWO JIMA.
In view of previous experience of having our SD radar detected
our policy now calls for sweeping continuously with the ST radar
with two (2) sweeps every half hour with the SJ. The SD radar
is never used except when the APR screen shows a saturated pip.

16 February 1945. 1200 Position: Lat. 32 - 10.5 N Long. 135 - 53.0 E.

0515 ST radar contact 050°T. 9,100 yds. (Ship contact #5.)
Commenced tracking.
0600 Problem solved. Target base course 180°T. Speed 12 knots.
Radical zigs. Decided to make a submerged attack at dawn as
the possibility existed that it might be a friendly submarine.
APR contact which rapidly became saturated on the screen.
0640 Plane contact at six (6) miles on the SJ radar. Submerged and
proceeded at high speed on course 180°T. Stalling for daylight.
0700 Identified target as a DESTROYER. Close observation of outline
details was not obtained as our fire control data was accurate
and periscope observations were kept to a minimum. At this time
I was convinced that this was a hunter-killer group and that
they had contacted us. The main feature observed was a single
stack well removed from the bridge structure. The closest
identification that can be made after examination of the Japanese
Recognition Manual is the FUBUKI CLASS DESTROYER.
The ST radar was working properly. Obtained first range at
3,750 yards with a quick four (4) foot exposure.

- 5 -

ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

0718 Range to target 1,850 yards. 85 degree track. Commenced firing
     stern tubes. Offset spread using periscope bearings. The first
     to hit the second one-half ship's length ahead and the third
     one-half ship's length astern. Started deep.
0719 Heard two (2) properly timed torpedo hits. Just prior to these
     explosions, we were rocked hard by two (2) aircraft bombs which
     according to the DCDI landed one (1) ahead to port and one (1)
     astern to starboard. Both below us. At the time we were
     passing 200 feet. The lights in the after torpedo room were
     knocked out, the antenna trunk flooded out, and the sea valves
     for the air conditioning circulating water were blown open and
     distorted. The echo ranging and the propellors of the target
     were immediately silenced.
0745 Periscope depth. Nothing in sight. Proceeded to scene of
     attack.
0830 Sighted large oil slick, debris, and approximately forty (40)
     Japs swimming in the water and hanging onto debris. No life
     boats or rafts afloat.
0845 Surfaced to attempt to take a prisoner. Unable to induce one
     to come aboard.
0911 SD contact. Range 12 miles. Submerged.
1213 Surfaced to again attempt to take prisoner aboard. Went
     alongside swamped life boat which contained five (5) Japs. Used
     all sorts of persuasion to get one aboard including Tommy gun
     fire close to them. Their chance of survival at this time was
     zero, as the water was cold, and yet they preferred to stay
     there instead of coming aboard.
1228 Sight contact with plane. Submerged.
     Circled underneath wreckage in hopes that we could get a crack
     at a rescue vessel.
1725 Surfaced.
1730 Sight contact on plane. Submerged.
1737 Heard pinging to the south. (Ship contact #6.) Thought this
     was a rescue vessel. This vessel's sound gear must have been
     very powerful as we did not sight the top of his masts until
     1820. I was convinced that he would come to us. The escort
     plane was circling over him. However he did not come even close
     and all that we were able to see was the tops of his masts. The
     sound conditions were exceptional and his turn count showed
     that he was making high speed. Believe he was a DESTROYER
     headed for BUNGO SUIDO.
1940 Surfaced in hot pursuit.
1954 SJ contact on plane distance 8 miles.
2014 Plane closed to four (4) miles. Submerged.
2110 Surfaced.
2314 PIR contact. Reached saturation. SD plane contact at 9 miles.
2316 Plane closed to 5 miles. Submerged.

- 6 -
ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

17 February 1945. 1200 Position: Lat. 31 - 32 N Long. 134 - 55 E.

0022 Surfaced.
0127 APR contact.
0254 SD contact 8 miles. Range increased and it faded out.
0655 Submerged.
1024 Surfaced.

18 February 1945. 1200 Position: Lat. 33 - 25 N Long. 135 - 35 E.

0107 APR contact 150 Mcs.
0122 APR contact faded out.
0553 Submerged to make close in sweep of SHIONO MISAKI.
1442 SHIONO MISAKI lighthouse bearing 005°T. ST radar range to
     land 4,300 yards.
2013 Surfaced. No activity of any sort was sighted.

19 February 1945. 1200 Position: Lat. 32 - 10 N Long. 136 - 00 E.

0119 APR contact 150 Mcs.
     Decided that, in view of the lack of activity near the beach
     and scheduled fleet operations, it would be expedient to
     remain on a line between KII SUIDO and IWO JIMA until fleet
     operations were completed.
0645 Submerged.
0915 Surfaced.
2000 Sent weather report. (SENNET #2.)

20 February 1945. 1200 Position: Lat. 32 - 10 N Long. 135 - 51 E.

0656 Submerged.
1104 Surfaced.
1347 Sighted floating Mine. (Type 45, 30 in. in diameter).
1428 A direct hit with a 40 MM shell exploded the mine. It made
     quite a fuss.
1617 SD contact 10 miles.
1618 Submerged.
1811 Surfaced.
2055 APR contact 85 Mcs. Faded out.
2200 APR contact 100 Mcs. Land based.

21 February 1945. 1200 Position: Lat. 32 - 38 N Long. 136 - 16 E.

0646 Submerged.
0942 Surfaced.
1821 APR contact 156 Mcs. Faded out.

- 7 -
ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

22 February 1945. 1200 Position: Lat. 32 - 40.5 N Long. 134 - 23.5 E.

0702 Submerged.
1108 Surfaced.
2000 Sent weather report. (SENNET #3.)

23 February 1945. 1200 Position: Lat. 33 - 25.5 N Long. 135 - 38 E.

0655 Submerged. Made close in sweep between ICHIYE SAKI and
SHIONO MISAKI.
SHIONO MISAKI light bearing 350°T. distance 2,500 yards.
1520 Surfaced.
2020 While passing ICHIYE SAKI saw smoke coming from several hills.
After dark this place gave off a bright red glow. The
following morning this had increased to include about 10 miles
of the coast eastward from ICHIYE SAKI. Several explosions
were noted by the OOD. No other activity sighted.

24 February 1945. 1200 Position: Lat. 33 - 24.5 N Long. 135 - 43 E.

0624 Submerged off ICHIYE SAKI light for close in sweep to SHIONO
MISAKI light.
0947 Heard pinging bearing 350°T.
1021 Battle stations submerged.
1026 JI heard screws bearing 000°T. Closed targets at high speed.
Targets identified as one (1) medium and one (1) small coastal
steamer with one (1) catcher type escort vessel. (Ship
contacts #7, 8, and 9.) The closest range attained was
4,000 yards on the last ship with a torpedo run of over 5,000
yards. Sighted numerous Sampans and two (2) small patrol
vessels during the day.
1645 Heard seven (7) distant depth charges.
2025 Surfaced.

25 February 1945. 1200 Position: Lat. 32 - 30 N Long. 134 - 40 E.

Conducted surface patrol on route from BUNGO SUIDO to BONIN
ISLANDS.
1930 Sent weather report. (SENNET #4.)

- 8 -
ENCLOSURE (A)

— page 48 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

26 February 1945. 1200 Position: Lat. 33 - 05 N Long. 135 - 20 E.
On lifeguard station thirty (30) miles southwest of SHIONO
MISAKI light.
1600 Submerged. No aircraft sighted. Apparently no strike was
made.

27 February 1945. 1200 Position: Lat. 32 - 56 N Long. 135 - 45 E.
On lifeguard station thirty (30) miles south of SHIONO MISAKI
light.
1400 Received message which canceled lifeguard duty.
1914 Surfaced.

28 February 1945. 1200 Position: Lat. 33 - 26 N Long. 135 - 38 E.
0610 Submerged ten (10) miles off ICHIYE SAKI light for close in
sweep to SHIONO MISAKI light.
No activity noted during the day.
1920 Surfaced. Sent weather report. (SENNET #5.). We were heckled
by radar equipped planes the remainder of the night.

1 March 1945. 1200 Position: Lat. 33 - 24 N Long. 135 - 50 E.
0530 Submerged eight (8) miles off ICHIYE SAKI light for close in
sweep to SHIONO MISAKI light.
Sighted four (4) small trawlers and at least 200 Sampans
during the day.
1135 Sighted two (2) small patrol boats making a sweep south of
SHIONO MISAKI light. They passed close aboard. They were echo
ranging on a frequency below the range of the JK sound gear
and above the range of the JP gear. It sounded as a clapping
noise on the JK sound gear. The two (2) echo ranged at an
interval of two (2) seconds and the other at one (1) second.
This ranging was not heard on the JP sound gear.
1922 Surfaced. Storm building up from the southwest. Decided to
make surface patrol away from land. SJ radar out of commission.

2 March 1945. 1200 Position: Lat. 32 - 40 N Long. 136 - 20 E.
Surface patrol on line between KII SUIDO and the BONIN ISLANDS.
Heavy seas from the south with rain and low visibility.

- 9 -
ENCLOSURE (A)

— page 49 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

3 March 1945.
1200 Position: Lat. 33 - 24 N. Long. 135 - 45 E.
Submerged ten (10) miles off ICHIYE SAKI light for close in
sweep to SHIONO MISAKI light.
0936 Heard echo ranging. Nothing in sight. Headed for the beach
at high speed.
1046 Sighted two (2) small unidentified ship's (Ship contacts #10
and 11) with four (4) small escorts. The closest range
attained on these vessels was 4,000 yards with a torpedo run
of 5,500 yards.
1927 Surfaced.
2030 Sent weather report. (SENNET #6.)

4 March 1945.
1200 Position: Lat. 32 - 49.0 N. Long. 136 - 06.5 E.
Surface patrol on line between KII SUIDO and the BONIN ISLANDS,
2209 proceeded to rendezvous with BOWFIN.

5 March 1945.
1200 Position: Lat. 31 - 00 N. Long. 138 - 00 E.
Rendezvous with BOWFIN. Received patient.
Set course for GUAM.

6 March - 9 March 1945.
Enroute GUAM.

(C) WEATHER:
The weather off KII SUIDO was very moderate for this season. Good
visibility, clear skies and moderate seas were the average conditions.

(D) TIDAL INFORMATION:
The current experienced off KII SUIDO for the entire patrol was
consistently 2.0 knots toward 095°T.

(E) NAVIGATION AIDS:
None of the light houses along the coast were lighted.
- 10 -
ENCLOSURE (A)

— page 50 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET. (SS408)

(F) SHIP CONTACTS:

NO. | TIME | LAT. | TYPE(S) | INITIAL | EST.COURSE | HOW CON- | REMARKS
    | DATE | LONG. |         | RANGE   | & SPEED    | TACTED   |
----|------|-------|||||
1 & 2 | 0146 | 30-04 N | 2 Picket | 10,800  | Lying to   | SJ Radar | Both sunk
    | 2-13 | 136-25 E| Boats   |         |            |          | by gunfire

3 & 4 | 0602 | 30-05 N | 2 Picket | 6,000   | Lying to   | SJ Radar | Both Damag-
    | 2-14 | 135-33 E| Boats   |         |            |          | ed by gun
    |      |       |         |         |            |          | fire.

5   | 0515 | 32-34 N | 1 DD    | 9,100   | 180°T.     | ST Radar | Sunk
    | 2-16 | 134-51 E|         |         | 12 knots   |          |

6   | 1737 | 32-11 N | 1 Ship Probably | -       | 320°T.     | Sound,Heard | Near scene
    | 2-16 | 134-50 E| a DD    |         |            | echo rang- | of sink-
    |      |       |         |         |            | ing      | ing other
    |      |       |         |         |            |          | DD.

7   | 0947 | 33-24 N | Catcher Type | 7,000   | 120°T.     | JK Heard |
    | 2-24 | 135-38 E| Patrol Vessel |         | 10 knots   | Pinging  |

8   | 0947 | 33-24 N | Medium Coast- | 7,000   | 120°T.     | JK Heard |
    | 2-24 | 135-38 E| al Steamer. |         | 10 knots   | Pinging  |

9   | 0947 | 33-24 N | Small Coastal | 7,000   | 120°T.     | JK Heard |
    | 2-24 | 135-38 E| Steamer. |         | 10 knots   | Pinging  |

10  | 1046 | 33-23 N | Small Coastal | -       | 280°T.     | JK Heard |
    | 3-3  | 135-40 E| Steamer |         | 8 knots    | Pinging  |

11  | 1046 | 33-23 N | Small Coastal | -       | 280°T.     | JK Heard |
    | 3-3  | 135-40 E| Steamer |         | 8 knots    | Pinging  |

(G) AIRCRAFT CONTACTS:

    Air search was encountered after radio transmissions and after
    attacks. All traffic along the coast was air escorted.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET                               TORPEDO ATTACK NO. 1.           PATROL NO. 2.

Time                                       Date                               Lat.                               Long.
0718 (K)                                   16 February 1945                   32 - 10 N.                         135 - 54 E.

                                           TARGET DATA

DESCRIPTION:                               One (1) DD.

DETERMINED:                                Two (2) timed torpedo hits. Twenty-five minutes after hits, ship
                                           not in sight. Propellors and echo ranging stopped immediately
                                           aftor hits. Large amount of debris and oil slick. Approximately
                                           fifty (50) survivors were in the water.

Ship's / Sunk                              One (1) DD.

Ship's / Damaged                           None
or probable sunk

Target Draft                               Course                             Speed                              Range
10 ft.                                     210                                12                                 1870

                                           OWN SHIP DATA

Speed                                      Course                             Depth                              Angle (at firing)
2.0                                        264                                62 ft.                             3 up

                                           FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK:                               Day, Submerged, Periscope.

                                           - 12 -

                                                                                                               ENCLOSURE (A)

— page 52 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

|                   | 7         | 8           | 9           |
| :| :| :| :|
| Tubes Fired       | 7         | 8           | 9           |
| Track Angle       | 81 S      | 87 S        | 83 S        |
| Gyro Angle        | 206 10    | 213         | 208         |
| Depth Set         | 4         | 4           | 4           |
| Power             | High      | High        | High        |
| Hit or Miss       | Hit       | Hit         | Miss        |
| Erratic           | No        | No          | No          |
| Mark Torpedo      | 23        | 23          | 23          |
| Serial            | 62586     | 53175       | 41341       |
| Mark Exploder     | 6-4       | 6-4         | 6-4         |
| Serial Number     | 18626     | 18771       | 18659       |
| Actuation Set     | Contact   | Contact     | Contact     |
| Mark Warhead      | 16-1      | 16-1        | 16-1        |
| Serial Number     | 3494      | 11765       | 12234       |
| Explosive         | Torpex    | Torpex      | Torpex      |
| Firing interval   | 0         | 10 S        | 10 S        |
| Spread            | Periscope | Periscope   | Periscope   |
| Sea Condition     | 2         | 2           | 2           |
| Overhaul Activity |           | U.S.S. FULTON (AS11) |             |

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

U.S.S. SENNET                               GUN ATTACK NO. 1                               PATROL NO. 2.

Time                     Date                     Lat.                     Long.
0735 (K)                 13 February 1945         30 - 04 N.               136 - 25 E.

DESCRIPTION: Two (2) Picket Boats - Approximately 300 Tons each.

Ship's / Sunk            Two (2) Picket Boats. Saw vessels burn and finally sink.
Ship's / Damaged         None.
or probable sunk

DETAILS OF ACTION: See NARRATIVE.

U.S.S. SENNET                               GUN ATTACK NO. 2                               PATROL NO. 2.

Time                     Date                     Lat.                     Long.
0749 (K)                 14 February 1945         30 - 05 N.               135 - 33 E.

DESCRIPTION: Two (2) Picket Boats - approximately 300 Tons each.

Ship's / Sunk:           None.
Ship's / Damaged:        Two (2) Picket Boats. Saw at least one (1) five inch hit
or probable sunk.                                 in one Picket Boat and two (2) five
                                                  inch hits in the other Picket Boat.
                                                  The 40 MM fire appeared to be
                                                  effective.

DETAILS OF ACTION: See NARRATIVE.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

(I) MINES:
     One (1) floating mine, Type 45 about 30 inches in diameter was
     encountered and destroyed by a direct hit with a 40 MM shell.

(J) ANTI-SUBMARINE MEASURES AND EVASION TACTICS:
     Nothing out of the ordinary was encountered in the way of anti-submarine
     measures except the patrol boats echo ranging on 12 Kcs. (See NARRATIVE).

(K) MAJOR DEFECTS AND DAMAGE:
     None.

(L) RADIO:
     While operating with the LAGARTO and HADDOCK, excellent use was made
     of the frequency modulated SCR equipment which was superior to the ship's
     VHF equipment. Authentication of traffic by use of shackle cipher was
     rapid and effective.
     The new whip antenna and the SD mast were used effectively for
     transmission of messages on the SCR equipment.

(M) RADAR:
     SJ- 1 Radar
     The performance of the SJ was in general very good. Only minor
     troubles were encountered in the maintenance of the SJ. Several 6 AC 7
     tubes had to be replaced in the IF strip, a 2X2 rectifier tube had to be
     replaced in the range indicator and 5 U 4 G rectifier tubes continued to
     give us trouble. The latter trouble will probably be remedied when
     5 R 4 G tubes can be obtained to replace the 5 U 4 G tubes. Until now
     the 5 R 4 G rectifiers have not been available.

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ENCLOSURE (A)

— page 56 —
U.S.S. SENNET (SS408)
C-O-N-F-I-D-E-N-T-I-A-L

(R) MILES STEAMED - FUEL USED.

SAIPAN to area                 1,180 miles 22,000 gallons
In area                        4,110 miles 44,000 gallons
Area to GUAM                   1,360 miles 25,000 gallons

(S) DURATION:

Days enroute to area           4
Days in area                   22
Days enroute to base           5
Days submerged                 7

(T) FACTORS OF ENDURANCE REMAINING:

Torpedoes                      Fuel         Provisions Personnel Factor

14                             22,000 gallons 30 days    30

Limiting factors this patrol - ComSubPac Orders.

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES:

RADAR COUNTERMEASURES:

SD-4 Radar

The SD was keyed once a minute to an from the area. In the area SD
was keyed twice on surfacing, once at 53 feet keel depth and again
immediately after surfacing. The SD was kept warmed up on the surface and
keyed when the APR gave a saturated pip on airborne frequencies.

SJ-1 Radar

During the patrol the SJ was kept continuously warmed up. To and from
the area SJ was used at night and during periods of low visibility. In
the area the SJ was used to take several sweeps every half-hour with the
ST being used continuously.

APR

The APR proved to be good aircraft warning device. It was manned
continuously while on the surface. In the area a number of aircraft con-
tacts were made and all of them were at 150 megacycles and 1,000 PRF. Only
one differed from the rest and it differed in its pulse shape and pulse
width.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES (Continued).

APR (Continued).
Instead of the pulse width being 8 to 11 microseconds it was approximately
17 microseconds. Most of the airborne radars picked up on the APR were
keyed erratically apparently to avoid detection.

One radar contact which was believed to be airborne was picked up at
124 megacycles. It had a pulse width of 5 microseconds and 1,750 PRF. At
the same time that the APR made contact with the above radar it picked up
another airborne radar at 150 megacycles and 1,000 PRF. These two radars
were keyed alternately indicating the possibility that one aircraft had
two different radars.

Since we were off SHIONO MISAKI during most of the patrol, every night
upon surfacing landbased radar was picked up on the APR. Most of these
landbased radars had an antenna rotation of three or four minutes.

The following are the landbased radars picked up off SHIONO MISAKI:

FREQUENCY | PRF | PULSE WIDTH
74 | 500 - 1000 | -
82 | 500 | 30
99 | 500 | 8
147 | 500 | 6
149 | 500 | 18
153 | 500 | 5
158 | 500 | 8

COMMUNICATIONS COUNTERMEASURES:
Heavy interference was encountered on all Wolf Pack frequencies while
SENNET was in assigned areas. Interference was principally CW, point to
point and random keying signals. Some voice interference was also
encountered at various periods.

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ENCLOSURE (A)

— page 58 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES (Continued).

COMMUNICATIONS COUNTERMEASURES (Continued).

     The 4235 Kcs. series was jammed very heavily while SENNET was in
assigned areas. At 1200 GCT, 14 February 1945, this vessel was unable to
clear a message on the 4235 Kcs. and 8470 Kcs., although VLM volunteered
to take a transmission. After attempts were made for one hour to clear the
message through VLM, atmospherics forced VLM to give up the effort. At
this time a shift was made to 4155 Kcs. and the message was cleared to
NPN 4 and NPN 17 in seventeen (17) minutes. Some jamming was encountered
on 4155 Kcs., but in no respect was it as heavy as on the 4235 series.

     Thereafter, all messages were cleared on 4155 Kcs. in reasonably short
times, with NPN 17, and later NPN 4, answering the calls at time of first
call.

     Sub fox schedules were copied without loss of any serials. Some jamming
was encountered, but this could be counteracted by a shift of frequencies.
To copy Sub fox the SENNET keeps one RAL - 8 and the RBS - 1 fed into a
mixing box at all times.

     NPN's signals on 9090 Kcs. were strength five. At times NPM and NPN
were not synchronized, and some difficulty was found in copying the
schedules.

SONAR COUNTERMEASURES

     Pinging was heard on approximately 12 Kc on two occasions.

(V) REMARKS.

     None.

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ENCLOSURE (A)

— page 59 —
FB5/281/A16-3
Serial ( 011
C-O-N-F-I-D-E-N-T-I-A-L

FIRST ENDORSEMENT to:
CO USS SENNET Conf. ltr
dated 9 March 1945.

From: The Commander Submarine Division TWO EIGHTY ONE.
To : The Commander-in-Chief, United States Fleet.
Via : (1) The Commander Submarine Squadron TWENTY EIGHT.
(2) The Commander Submarine Force, PACIFIC FLEET.

Subject: U.S.S. SENNET (SS408) - Report of War Patrol Number TWO.

1. The second war patrol of SENNET was of thirty-one days duration,
twenty-two of which were spent in the assigned areas. Seven days were spent
submerged.

2. In the first phase of this patrol SENNET was a member of a task
group which also included U.S.S. LAGARTO (Commander F. D. LATTA, Task Group
Commander) and U.S.S. HADDOCK. The mission of this group was to destroy enemy
picket boats in the open sea south of the Japanese Empire.

3. In the early hours of 13 February 1945, the group established radar
contact with two enemy picket boats and maneuvered to be in a favorable position
for a dawn attack with deck armament. The action commenced at 0735 and by 0820
both enemy ships had been destroyed by the concentrated fire of the group at
ranges varying from 6500 yards to point blank.

4. Near midnight of the same day a second group of two pickets was
discovered by radar and again the group was disposed for a concerted dawn attack.
At 0749, on 14 February, LAGARTO and SENNET opened fire, the HADDOCK being submer-
ged, and continued to engage the enemy at ranges varying from 5000 to 1800 yards
until 0817 when expenditure of all five inch ammunition forced them to break off
and retire leaving the enemy damaged but still afloat and under command. During
the course of this action the enemy replied with accurate fire from moderate
caliber guns and small arms. SENNET received at least two hits; material damage
was superficial but one man was wounded by a fragment.

5. At 0900, 14 February, SENNET was released by the Task Group
Commander and proceeded to her assigned patrol area south of KII SUIDO. The
remainder of the patrol followed the usual pattern of this area; frequent air-
craft contacts both by day and by night, and few ship contacts.

6. About two hours before dawn on the morning of 16 February contact
was made with an unknown ship by ST radar. The commanding officer elected to
track until dawn in order to establish beyond a doubt the enemy character of this
contact. This prudent plan nearly went sadly amiss when the arrival of radar
equipped air escort forced SENNET to submerge before there was yet enough light
for a periscope attack. However, by proceeding along the basic course at high

-1-
SUBMARINE DIVISION TWO EIGHTY ONE
Care of Fleet Post Office,
San Francisco, California.
10 March, 1945.

— page 60 —
SUBMARINE DIVISION TWO EIGHTY ONE

                                                                Care of Fleet Post Office,
                                                                San Francisco, California.
                                                                10 March, 1945.

FB5/281/A16-3

Serial (011)

C-O-N-F-I-D-E-N-T-I-A-L

Subject:        U.S.S. SENNET (SS408) - Report of War Patrol Number TWO.

— page 61 —
FC5-28/A16-3
Serial No. 072.
C-O-N-F-I-D-E-N-T-I-A-L

SUBMARINE SQUADRON TWENTY-EIGHT

Care of Fleet Post Office,
San Francisco, California.
12 March 1945.

SECOND ENDORSEMENT to:
CO, USS SENNET Conf. ltr. A16-3
Serial No. 04-45 dated 9 March
1945.

From: The Commander Submarine Squadron TWENTY-EIGHT.
To : The Commander-in-Chief, United States Fleet.
Via : (1) The Commander Submarine Force, PACIFIC FLEET.
(2) The Commander in Chief, United States Pacific Fleet.

Subject: U. S. S. SENNET (SS408) - Report of War Patrol Number TWO.

1. Forwarded, concurring in the remarks of the Commander Submarine
Division TWO EIGHT ONE in the first endorsement.

2. The Commander Submarine Squadron TWENTY-EIGHT congratulates the
Commanding Officer, officers and crew on the successful completion of the
SENNET'S second war patrol, during which the following damage is considered
to have been inflicted upon the enemy:

SUNK
1 DD(Similar to FUBUKI)(EU) 1,800 tons (Attack#1)
2 Picket Boats(EC) * 600 tons (Gun Attack #1)

*To be shared with HADDOCK and LAGARTO

DAMAGED
2 Picket Boats(EC) * 600 tons (Gun Attack #2)

* To be shared with LAGARTO

[SIGNATURE: Illegible]
J. R. WILL.

— page 62 —
[HANDWRITTEN: F4254] 4 0405
mr
FF12-10(A)/A16-3(18) SUBMARINE FORCE, PACIFIC FLEET
Serial 0632 Care of Fleet Post Office,
San Francisco, California,
CONFIDENTIAL 26 March 1945.
THIRD ENDORSEMENT to NOTE: THIS REPORT WILL BE
SENNET Report of DESTROYED PRIOR TO
Second War Patrol. ENTERING PATROL AREA.

COMSUBSPAC PATROL REPORT NO. 696
U.S.S. SENNET - SECOND WAR PATROL.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander-in-Chief, United States Fleet.
Via : The Commander-in-Chief, U.S. Pacific Fleet.

Subject: U.S.S. SENNET (SS408) - Report of Second War Patrol
(7 February to 9 March 1945).

1. The second war patrol of the SENNET, under the com-
mand of Commander G. E. Porter, U.S. Navy, was conducted south of the
Japanese Empire and off Kii Suido.

2. During the first phase of this patrol the SENNET,
along with the U.S.S. HADDOCK (SS231) and the U.S.S. LAGARTO (SS371),
operated as a group, under the command of the commanding officer of
the LAGARTO, to destroy enemy picket boats in the open sea south of
the Japanese Empire. Contact was made with two pairs of picket boats,
and two aggressive gun attacks were made, resulting in sinking two of
the picket boats and severely damaging the other two. The SENNET then
proceeded to Kii Suido, and with an excellently planned, aggressive
attack sank a FUBUKI Type destroyer.

3. Award of Submarine Combat Insignia for this patrol
is authorized.

4. The Commander Submarine Force, Pacific Fleet, con-
gratulates the commanding officer, officers and crew for this well
planned, aggressive, successful patrol. The SENNET is credited with
having inflicted the following damage upon the enemy during this pa-
trol:

S U N K

1 - DD (Similar to FUBUKI Type)(EU)-1,800 tons (Attack No. 1)
*1/3 - MIS. (Picket Boat) (EC) - 100 tons (Gun Attack No.1)
*1/3 - MIS. (Picket Boat) (EC) - 100 tons (Gun Attack No.1)

TOTAL SUNK 2,000 tons

*Credit for sinking these 300 ton picket boats shared with HADDOCK
and LAGARTO. [STAMP: EXTRA]
[STAMP: SORG.]
[STAMP: PHOTO-LAB OP-16]
[STAMP: RETURN TO F-4253]

- 1 -

— page 64 —
U.S.S. SENNET (SS408)
                                                                Care of Fleet Post Office,
                                                                San Francisco, California.
                                                                16 May 1945

SS408/A16-3
Serial: 05-43
C-O-N-F-I-D-E-N-T-I-A-L
[STAMP: DECLASSIFIED]
[STAMP: DECLASSIFIED-ART. 0445, OPNAVINST 5510.1C]
BY [SIGNATURE: J. L. Porter]
DATE [HANDWRITTEN: 6/10/72]

From: The Commanding Officer.
To: The Commander-in-Chief, United States Fleet.
Via: (1) The Commander Submarine Division 102.
     (2) The Commander Submarine Squadron 10.
     (3) The Commander Submarine Force, Pacific Fleet.
     (4) The Commander-in-Chief, U. S. Pacific Fleet.

Subject: U.S.S. SENNET - Report of War Patrol Number THREE.

Enclosure: (A) Subject Report.

1. Enclosure (A), covering the Third War Patrol of
this vessel conducted in the area off KII SUIDO during the
period from 3 April 1945 to 16 May 1945, is forwarded herewith.

                                                                [SIGNATURE: J. L. Porter]
                                                                J. L. PORTER.

[HANDWRITTEN: FILMED]
[HANDWRITTEN: 123263]

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C-O-N-F-I-D-E-N-T-I-A-L

(A) PROLOGUE:

Arrived GUAM on 9 March 1945. Refit accomplished by U.S.S. APOLLO,
under the direction of Commander Submarine Squadron TWENTY EIGHT.

During the refit, this vessel was dry docked to rewood both strut
bearings and to stop a fuel leak in expansion tank.

Five days operations, one for post repair trial and four for training
gave sufficient time for training. Excellent target services were available
for torpedo exercises. A suitable target for gunnery practice was not
available.

The material condition of the ship at the start of this patrol was the
best attained to date. This is directly attributed to the efficient work
of the relief crew and tender repair force. The cooperation of the relief
crew commanding officer, Lieutenant Commander R. HOLDEN during this refit
is highly commendable.

During the refit period, the following transfers were effected:

DETACHED: NONE

REPORTED: Ensign George H. SWANSON, EL, USNR.

TRANSFERRED: Five(5) Enlisted Men.

RECEIVED: Seven (7) Enlisted Men.

The following officers are on board:

NAME                                        PREVIOUS WAR PATROLS

Comdr., George E. PORTER, jr.               THREE (3) BLUEFISH
                                            THREE (3) GREENLING
                                            TWO   (2) SENNET

Lieut-Comdr., Charles R. CLARK, jr.         TWO   (2) DACE
                                            TWO   (2) SENNET

Lieut., James D. ROCHE                      ONE   (1) BLUEFISH
                                            TWO   (2) SENNET

Lieut., Frank A. ANDREWS                    TWO   (2) SENNET

Lt.(jg), MC "B" KOSSERT                     FOUR  (4) GREENLING
                                            TWO   (2) SENNET

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

(A) PROLOGUE (Continued):

Lt.(jg), Vesper E. BURKS
                                        TWELVE (12) THRESHER
                                        TWO (2) SENNET
Lt.(jg), John H. VAN NESS
                                        TWO (2) SENNET
Ensign, George H. SWANSON
                                        NONE
Ensign, Donnell H. WAGNER
                                        TWO (2) SENNET
Ensign, Elmer V. ANDERSON
                                        FIVE (5) CLUEFISH
                                        TWO (2) SENNET
Torpedoman, James M. GETTLE
                                        EIGHT (8) S-18
                                        ONE (1) SENNET

The following CPO's are on board during this patrol:

NAME                                    RATE            PREVIOUS WAR PATROLS

BIRCHARD, Mervale B.,                   CGM(PA)         FOUR (4) GREENLING
                                                        TWO (2) SENNET
REILLY, Tex D.,                         CTM(AA)(T)      FIVE (5) POGY
                                                        TWO (2) SENNET
EPLER, George W.,                       CSM(PA)         THREE (3) CUTTLEFISH
                                                        TWO (2) SENNET
GOLLADAY, Elmer C.,                     CRM(PA)         TWO (2) SENNET
KARETNUK, Anthony (n),                  CMOMM(PA)       NINE (9) SWORDFISH
                                                        TWO (2) SENNET
HALL, Leon W.,                          CMOMM(T)        FOUR (4) S-45
                                                        TWO (2) SENNET
COGHILL, Kettig S.,                     CMOMM(T)        ONE (1) BALAO
                                                        ONE (1) SENNET
BRENGELMAN, Henry B.,                   CEM(PA)         EIGHT (8) SEAWOLF
                                                        ONE (1) SARGO
                                                        TWO (2) SENNET
DAWSON, Ralph O.,                       CPhM(PA)        FIVE (5) GREENLING
                                                        TWO (2) SENNET

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

(B) NARRATIVE:

Actions of this vessel which are top secret have been omitted and are
the subject of a separate report.

(All times will be KING unless otherwise specified).

3 April 1945.
1500 (K) Underway for patrol area off KII SUIDO in accordance with
Commander Task Force SEVENTEEN Operation Order No. 73-45.

4 April 1945.
1200 Position: Lat. 16 - 39 N. Long. 139 - 57 E.
1310 Made trim dive.
Routine training enroute area.

5 April 1945.
1200 Position: Lat. 21 - 13 N. Long. 137 - 23 E.
1450 Made trim dive.
Routine training enroute area.

6 April 1945.
1200 Position: Lat. 26 - 46 N. Long. 137 - 19 E.
1200 Received Comsubpacadcom 052317. Continued at maximum speed
toward western end of Corridor.
2022 Received USS THREADFIN contact report of task force.
Maximum speed to intercept.
2100 George's Gangsters formed by order of ComSubPac consisting of
USS TRUTTA, USS LIONFISH and USS SENNET.

7 April 1945.
1200 Position: Lat. 29 - 30 N. Long. 132 - 07.5 E.
0214 APR contact 150 Mqs. Faded out.
0714 Sighted floating Mine. Did not destroy same due to other
urgent activity.
0800 Unable to intercept task force. Formed scouting line with
USS LIONFISH, USS TRUTTA and USS SENNET on Lat. 31 - 30 N.
off BUNGO SUIDO.
0905 SD contact. 11 Miles, moving out.
1107 Changed base course to 000°T.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

1204 Sighted floating Mine.
1208 Sighted submarine bearing 045°T. Distance about 8 Miles.
     He dove before we could identify him.
1351 SD contact 18 Miles. Faded out.
1420 Sighted USS TENCH. Went close aboard to exchange information.
1602 Sighted 2 Hellcats.
2036 ST radar interference, bearing 105°.
2103 APR contact 155 Mcs. Faded out.
2137 APR contact 137 Mcs. Faded out.

8 April 1945.
     1200 Position: Lat. 29 - 30 N. Long. 132 - 32 E.

0612 Submerged.
0847 Sighted RUFE type float plane heading South.
1003 Sighted RUFE type float plane heading North.
1120 Surfaced.
1137 Submerged. Unidentified plane sighted by lookout.
1428 Surfaced.
1435 SD contact 19 Miles.
1437 APR contact 160 Mcs.
1443 SD and APR contact faded out.
1740 Sighted empty torn up life raft.
1928 Sighted USS LIONFISH.
2158 George's Gangsters disolved by despatch from ComSubPac.
2217 Enroute KII SUIDO.
2322 Zoomed by PBM.
2325 Submerged.
2340 Surfaced.

9 April 1945.
     1200 Position: Lat. 32 - 27 N. Long. 133 - 42.5 E.

0146 APR contact 156 Mcs. Land Based.
0613 Submerged.
1546 Surfaced.
1551 APR contact 98 Mcs.
2216 Headed in for sweep of coast between ICHIE SAKI and SHIONO MISAKI.
2225 APR contact 150 Mcs. Land Based.
2345 APR contact 153 Mcs. Land Based.

10 April 1945.
     1200 Position: Lat. 33 - 00 N. Long. 136 - 03.5 E.

0027 APR contact 151 Mcs. Land Based.
0130 Sighted light on beach.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

0235             APR contact 147 Mcs. Land Based.
0240             Headed south.
0330             Received ComSubPac 091244. Proceeded toward lifeguard station.
0557             Sighted exhaust of plane. Submerged.
1530             Surfaced.
2147             Received ComSubPac 100611. Cancelling lifeguard assignment.

11 April 1945.
                 1200 Position: Lat. 33 - 02 N. Long. 136 - 34 E.
0345             Sent SENNET serial No. ONE.
0607             Submerged.
1504             Surfaced.
2046             APR contact 150 Mcs. Land Based.
2132             APR contact 153 Mcs. and 82 Mcs. Land Based.

12 April 1945.
                 1200 Position: Lat. 32 - 53 N. Long. 133 - 08 E.
0310             APR contact 100 Mcs. Land Based.
0620             Submerged for close in sweep from ASHIZURI SAKI to MUROTO SAKI.
1917             Surfaced.
2030             Lying to.

13 April 1945.
                 1200 Position: Lat. 33 - 23 N. Long. 133 - 55 E.
0204             APR contact 152 Mcs. Airborne.
0308             Lost contact.
0436             Underway for position off KOCHI.
0558             Submerged.
0704             Sighted Lugger. Enroute MUROTO SAKI. (Ship Contact No. 1).
0928             Sighted Sea Truck enroute MUROTO SAKI. (Ship Contact No. 2).
1337             Sighted squadron of planes.
2018             Surfaced.
2038             Lying to.

14 April 1945.
                 1200 Position: Lat. 33 - 21.5 N. Long. 133 - 53 E.
0525             Underway for position off KOCHI.
0610             Submerged.
0728             Sighted six (6) fishing vessels.
1025             Sighted Sea Truck enroute MUROTO SAKI. (Ship Contact No. 3).
2018             Surfaced.
2300             Lying to.
2332             ST contact on plane 8,500 yds.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

2334 Submerged.
2344 Surfaced. Lying to.

15 April 1945.
1200 Position: Lat. 33 - 15 N. Long. 136 - 16 E.

0358 Underway for vicinity of MIKI SAKI.
1341 APR contact 155 Mcs. Faded out.
1502 Submerged ten (10) Miles off MIKI SAKI.
1708 Sighted large Sampan heading toward beach.
2010 Surfaced.
2159 SJ contact 5,000 yds.
2324 Closed contact to 200 yds. Found it to be a small fishing vessel
heading into port. It was too dark for gunfire.

16 April 1945.
1200 Position: Lat. 32 - 55 N. Long. 134 - 25 E.

0610 Submerged.
1530 Surfaced.
2100 10 CM. radar interference 260°T.
2214 Sighted lights on beach.
2222 SJ contact 190°T. 26,000 yds. Three (3) large pips. (Ship
Contacts Nos. 4, 5, and 6). Range opening rapidly. Tracked on
course 240°T. at speed 25.
2256 Sighted two (2) torpedo wakes. One (1) ahead, one (1) astern.
The prompt action of the O.O.D. (Lieut., F.A. ANDREWS) in ordering
full right rudder probably saved this ship. We passed through
the wake of one torpedo.
2257 Submerged.
2332 Surfaced. Sent contact report, SENNET Serial No. TWO.
2337 SJ contact 4,000 yds. 090°T. Straddled again by torpedoes.
2338 Submerged. Received a "ROGER" for our contact report as we were
diving.

17 April 1945.
1200 Position: Lat. 32 - 54.5 N. Long. 134 - 48.0 E.

0034 High speed light screws. 070°T.
0054 Surfaced. 10 CM. interference and three (3) SJ contacts bearing
100°T. Distance 1,800 yds.
0059 Submerged.
0114 Sound contacts. Four (4) sets of light fast screws 255°T. to
010°T.
0701 Surfaced. Sent amplifying contact report to ComSubPac. SENNET
Serial No. THREE.
0742 Sent SENNET Serial No. FOUR.
1133 Submerged.

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C-O-N-F-I-D-E-N-T-I-A-L

1807 Surfaced.
2014 Lying to.
2107 SJ interference 150°T.
Contacted USS PICUDA. Exchanged information via VHF. He had
experienced trouble with 10 CM. interference last night.

18 April 1945.
1200 Position: Lat. 33 - 07 N. Long. 135 - 38.5 E.

0109 Lost contact with USS PICUDA.
0115 Zoomed by plane. Submerged.
0147 Surfaced.
0148 APR contact 154 Mcs. PRF 500.
0151 Strafed by plane. Submerged. This was on a pitch black night.
He passed from bow to stern at about 100 feet.

COMMENT: We have been catching too much HELL. It's about time
we dished some out.

0435 Surfaced.
0550 Submerged.
1454 Surfaced.

19 April 1945.
1200 Position: Lat. 33 - 20 N. Long. 135 - 40 E.

0530 Submerged for close in sweep between ICHITYE SAKI and SHIONO MISAKI.
0716 Sighted ship bearing 357°T, 8,000 yds.
0759 Target was a Medium AK. Similar to KIMISIMA MARU with one (1)
large escort, four (4) small escorts and one (1) small SUGAR DOG.
(Ship Contacts Nos. 7, 8, 9, 10, 11, and 12).
0823 Fired three (3) MK18 torpedoes at AK. Spread by periscope one to
hit one a half ships length ahead, and one a half ships length a
stern.
0826 Saw one (1) torpedo hit amidships. (Attack No. 1).
0827 Target listed to starboard with deck awash amidships. Bow and
stern were elevated as though its back was broken. Could not
wait any longer as five (5) escorts were close and coming in fast.
Started deep and headed for 100 fathom curve.
0833 Received two (2) depth charges.
0835 Received two (2) depth charges.
0840 Received two (2) depth charges.
0843 Hit bottom at 285 feet. Rigged in sound heads, which were saved
by up angle. Ran at 50 feet off bottom and took soundings with
Fathometer until reaching 100 fathom curve.
0846 Received one (1) depth charge.
0848 Lowered one (1) sound head.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

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0925 Received six (6) depth charges.
0931 Escorts started pinging (Low Frequency) for first time.
0957 Two (2) depth charges. Too far to register on DCDI.
1438 Lost contact with escorts.
2001 Surfaced.
2158 Sighted plane distance 4 Miles. Submerged.
2223 Surfaced.
2350 Sent SENNET Serial No. FIVE.

20 April 1945. 1200 Position: Lat. 33 - 03 N. Long. 135 - 02 E.

0540 Submerged.
2036 Surfaced.

21 April 1945. 1200 Position: Lat. 33 - 26 N. Long. 135 - 32 E.

0101 SD contact 6 Miles. Submerged.
0147 Surfaced.
0505 Submerged for close in sweep between ICHIYE SAKI and SHIONO MISAKI.
0712 Sighted three (3) patrol boats.
0715 Sighted large fishing vessel.
0832 Sighted one SUGAR CHARLIE SUGAR with one large "PC" type and one
     small catcher type escort vessel. (Ship Contacts Nos. 13, 14,
     and 15). Could not close for attack.
0938 Sighted one SUGAR CHARLIE SUGAR with three (3) CATCHER type
     escorts headed up the coast. (Ship Contacts Nos. 16, 17, 18, and
     19). Commenced approach.
0955 Sighted three (3) CATCHER type patrol boats (Ship Contacts Nos.
     20, 21, and 22) approaching from the south. Fishing boats and
     sail boats were numerous in all directions. Sea glassy calm.
     Best position attained on the SUGAR CHARLIE SUGAR was at a range
     of 3,000 yards with a 160° track. Decided not to fire when at:-
1006 Sighted a medium AK with one CATCHER type escort. (Ship Contacts
     Nos. 23 and 24). Angle on bow 10° port. A good set up. Closed
     to a position of angle on the bow 50° port, range 3,000 yards
     when he zigged radically away as though he had detected us. The
     group of three (3) escort vessels (Ship Contacts Nos. 20, 21, and
     22)headed for us. Believe we were spotted by a plane.
1055 Forced deep by escorts which remained with us most of the day but
     must have been out of depth charges.
2037 Surfaced.

22 April 1945. 1200 Position: Lat. 34 - 00 N. Long. 137 - 00 E.

0329 ST contact on plane 9,000 yds. Faded out at 16,000 yds.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

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0545 Submerged on lifeguard stations.
1206 Surfaced. Super Dumbo in sight.
1228 Sighted P-51. He was firing guns and dropped gas tank to attract
our attention.
1230 Pilot bailed out and plane crashed about 3,000 yds. ahead of us.
1234 Pilot went under about 100 feet off bow. Sent Lieutenant F.A.
ANDREWS over side. Just missed. This was a heart breaker.
Recovered pilots chart.
1328 Super Dumbo left, no other planes down.
1332 Submerged.
2005 Surfaced.

23 April 1945. 1200 Position: Lat. 32 - 54 N. Long. 133 - 37 E.

0556 Submerged.
0349 Surfaced.
1459 Submerged.
2021 Surfaced.
2308 Sent SENNET Serial No. SIX.
2330 SD contact 7 Miles. Moved in to 4 Miles. Submerged.

24 April 1945. 1200 Position: Lat. 32 - 55 N. Long. 135 - 40 E.

0036 Surfaced.
0546 SJ plane contact 4,700 yds.
0552 Submerged.
1114 Heard five (5) distant depth charges.
1448 Surfaced.
1537 Submerged.
2013 Surfaced.

25 April 1945. 1200 Position: Lat. 34 - 04 N. Long. 136 - 23 E.

0613 Submerged for close in patrol off MIKI SAKI.
2002 Surfaced.

26 April 1945. 1200 Position: Lat. 33 - 52 N. Long. 136 - 14 E.

0527 Submerged for close in patrol off MIKI SAKI.
0923 Sight two (2) small patrol boats. Headed down the coast.
(Ship Contacts Nos. 25 and 26).
1145 Sighted float plane RUFE. Distance about three (3) Miles.
2040 Surfaced. Stayed on line from IRO SAKI to SHIONO MISAKI.
APR out of commission.

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ENCLOSURE (A)

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C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

27 April 1945.
1200 Position: Lat. 33 - 56 N. Long. 136 - 20 E.

0224         SD contact 4 Miles.
0524         Submerged for close in patrol off MIKI SAKI.
2029         Surfaced.

28 April 1945.
1200 Position: Lat. 33 - 50 N. Long. 136 - 31 E.

0454         Submerged for close in patrol off MIKI SAKI.
0702         Sound picked up pinging. (Ship contact No. 27). Commenced
             approach. Target appeared to be a NAVAL CABLE LAYER. It had the
             lines of an overgrown DESTROYER.
0732         Commenced firing. (Attack No. 2). Fired two (2) Mark EIGHTEEN
             torpedoes on a 100° track. Range 2,700 yards. Spread one at
             foremast and one at mainmast. Remaining torpedoes were Mark TWENTY-
             THREE and decided to await results of electrics before firing the
             air torpedoes. Saw the first torpedo blow his bow off and the
             second hit under the mainmast. Ship was down by the stern but not
             sinking.
0747         Fired one torpedo at stopped target. (Attack No. 3). Range 2,900
             yards. Zero gyro angle. MISSED.
0750         Two (2) small patrol boats appeared at the scene.
0754         Fired two (2) torpedoes at target. Range 3,200 yards. Zero gyro
             angle. MISSED. Decided not to fire any more torpedoes as ship
             was slowly sinking by the stern.
0830         Ship stood on end and went down by the stern.
             During this action two (2) rolls of colored films were taken and
             identification of the target should be facilitated. Patrol boats
             dropped a few random depth charges.
2014         Surfaced.
2113         Submerged. Plane contact 5 Miles.
2304         Surfaced.

29 April 1945.
1200 Position: Lat. 32 - 51 N. Long. 135 - 29 E.

0143         Sent SENNET Serial No. SEVEN to ComSubPac.
0535         Submerged off KII SUIDO.
1825         Surfaced.
1930         Exploded floating Mine.

30 April 1945.
1200 Position: Lat. 32 - 53 N. Long. 135 - 04 E.

0536         Submerged off KII SUIDO.
1423         Surfaced.
1455         Submerged.
1909         Surfaced.

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ENCLOSURE (A)

— page 75 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

1 May 1945.
1200 Position: Lat. 33 - 20 N. Long. 135 - 40 E.

0442 Submerged for close in sweep from ICHIYE SAKI to SHIONO MISAKI.
0821 Sound picked up echo ranging. (Ship contact No. 28). Commenced
     approach. Target identified as an ASASHIO CLASS DESTROYER.
0831 Fired five (5) air torpedoes. (Attack No. 4). Range 1,900 yards
     on a 100° track. Spread by periscope one amidships one a quarter
     ships length astern, one a quarter ships length ahead, one a ships
     length astern, and one a ships length ahead. Our control setup
     was good as the ST radar ranges came in good from 5,000 yards.
0835 Target maneuvered to avoid torpedo tracks and succeeded.
0848 Started deep using fathometer for sounding.
2045 Target laid a barrage of three (3) depth charges. The center one
     of this barrage was the closest we have taken to date and shook us
     considerably. DESTROYER turned the hunt over to three (3) Patrol
     boats and shoved off. The DESTROYERS appear to be afraid of
2135 submarines. Depth charges dropped until 1100. None close.
2142 Surfaced.
2145 Sent SENNET serial No. EIGHT to ComSubPac.
     Plane contact closed to 9 miles and then faded out.
     Set course for SAIPAN.

3 May 1945.

0630 Contacted SCABBARDFISH and delivered ECM.

6 May 1945.

Arrived SAIPAN.

7 May 1945.

Departed SAIPAN

7 May 1945 - 16 May 1945.

Enroute Pearl Harbor.
Conducted routine training enroute.

16 May 1945.

Arrived Pearl Harbor.

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ENCLOSURE (A)

— page 76 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

(C) WEATHER:

The weather was moderate during all of the patrol. The sea was glassy
calm several days.

(D) TIDAL INFORMATION:

The only tide and current experienced was the normal Japan stream
current with an easterly set of 1.5 to 2.0 knots.

(E) NAVIGATIONAL AIDS:

No navigational lights were sighted.

The best aid to navigation we had was the LORAN EQUIPMENT. Off the
Empire we could get a longitude line accurate within five miles at night
which is the main concern in this area.

Enroute to and from the area the equipment gave excellent fixes. The
best time to take readings at extreme distances from the stations was
found to be just after sunset and just before sunrise.

(F) SHIP CONTACTS:

See page 13.

(G) AIRCRAFT CONTACTS:

After attacks and immediately after transmitting, search aircraft
covered the area thoroughly and getting in a battery charge caused
considerable concern.

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ENCLOSURE (A)

— page 77 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(F) SHIP CONTACTS:

NO. | TIME | LAT. | TYPE(S) | INITIAL RANGE | EST.COURSE | EST.CON. REMARKS
    |      | LONG. |         |               | & SPEED   | & D
----|------|-------||||
1   | 0704 | 33-20 N | LUGGER  | 6,000         | 140       | Periscope
    | 4-13 | 133-41 E|         |               | 5         |
2   | 0928 | 33-21 N | SEA TRUCK | 6,000         | 137       | Periscope
    | 4-13 | 133-44 E|         |               | 5         |
3   | 1025 | 33-23 N | SEA TRUCK | 6,000         | 130       | Periscope
    | 4-14 | 133-49 E|         |               | 5.5       |
4,5 | 2222 | 33-17 N | TASK FORCE | 26,000        | 240       | SJ RADAR
& 6.| 4-16 | 133-51 E|         |               | 25        |
7,8,| 0716 | 33-35 N | 1 MEDIUM AK | 8,000         | 157       | Periscope Attack
9,10,| 4-19 | 135-21 E| 1 SUGAR DOG |               | 6         | #1
11,12.|      |       | 4 ESCORTS |               |           |
13, | 0832 | 33-32 N | 1 SUGAR CHARLIE | 6,000         | 120       | Periscope
14,&| 4-21 | 135-28 N| SUGAR   |               | 8         |
15. |      |       | 1 LARGE ESCORT |               |           |
    |      |       | 1 SMALL ESCORT |               |           |
16,17,| 0938 | 33-32 N | 1 SUGAR CHARLIE | 6,000         | 300       | Periscope
18, &| 4-21 | 135-28 E| SUGAR   |               | 8         |
19. |      |       | 3 ESCORTS |               |           |
20,21,| 0955 | 33-32 N | 3 ESCORTS | 5,000         | Patrolling| Periscope
& 22.| 4-21 | 135-28 E|         |               |           |
23  | 1006 | 33-32 N | 1 MEDIUM AK | 6,000         | 120       | Periscope
24  | 4-21 | 135-28 E| 1 ESCORT |               | 6         |
25  | 0923 | 33-57 N | 2 PATROL BOATS | 6,000         | 2000      | Periscope
26  | 4-26 | 136-18 E|         |               | 6         |
27  | 0702 | 33-58 N | CABLE LAYER | 10,000        | 214       | JK HEARD Attack
    | 4-28 | 136-17 E|         |               | 9.5       | PINGING #2&3
28  | 0821 | 33-28 N | DESTROYER | 4,800         | 295       | JK HEARD Attack
    | 5-1  | 135-32 E| ASASHIO CLASS |               | 12        | PINGING #4.

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ENCLOSURE (A)

— page 78 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET TORPEDO ATTACK NO. 1. PATROL NO. 3.

Time Date Lat. Long.
0827 (K) 19 April 1945 33 - 35 N. 135 - 23 E.

TARGET DATA

DESCRIPTION: Similar to KINISIMA MARU (Page 118 in ONI 208-J).

DETERMINED: Periscope observation of hit amidships. Last sighted with
target listed to starboard with deck awash amidships. Bow and
stern were elevated as though its back was broken.

Ship's / Sunk: NONE

Ship's / Damaged
or probable sunk: ONE

Target Draft Course Speed Range
10 Ft. 157 6 2740

OWN SHIP DATA

Speed Course Depth Angle (at firing)
2.5 70 60 Ft. 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

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ENCLOSURE (A)

— page 79 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

Tubes Fired                               1             2             3
Track Angle                             113 S         116 S         113 S
Gyro Angle                              020° - 30' R  023° - 10' R  020° - 30' R
Depth Set                               6'            6'            6'
Power                                   27.5          27.5          27.5
Hit or Miss                             Hit           Miss          Miss
Erratic                                 No            No            No
Mark Torpedo                            18-1          18-1          18-1
Serial                                  55610         54561         56819
Mark Exploder                           8-5           8-5           8-5
Serial Number                           9958          7958          8874
Actuation Set                           Contact       Contact       Contact
Mark Warhead                            18-2          18-2          18-2
Serial Number                           3634          3259          3476
Explosive                               Torpex        Torpex        Torpex
Firing Interval                         0             10 S          17 S
Spread                                  Periscope     Periscope     Periscope
                                        0             200' R        200' L
Sea Condition                           2             2             2

Overhaul Activity                       U.S.S. APOLLO (AS25)
Remarks: Injection temperature 65°F. Temperature of 60°F. used for
          speed correction.

                                        - 15 -

                                                              ENCLOSURE (A)

— page 80 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET TORPEDO ATTACK NO. 2. PATROL NO. 3.

Time Date Lat. Long.
0732 (K) 28 April 1945 33 - 58 N. 136 - 17 E.

TARGET DATA

DESCRIPTION: CABLE LAYER
DETERMINED: Periscope observation by Commanding Officer of two (2) hits and
later sinking of ship.

Ship's / Dunk: One 3,000 Ton CABLE LAYER.
Ship's / Damaged
or probable sunk: NONE

Target Draft Course Speed Range
12 Ft. 21340 9.5 2690

OWN SHIP DATA

Speed Course Depth Angle (at firing)
2 ¼ 320 60 Ft. 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA (Continued).

Tubes Fired                 1             2
Track Angle                 103 P         104 P
Gyro Angle                  332-10        330-40
Depth Set                   6             6
Power                       27.5          27.5
Hit or Miss                 Hit           Hit
Erratic                     No            No
Mark Torpedo                18-1          18-1
Serial Number               56777         55512
Mark Exploder               8-5           8-5
Serial Number               8130          9470
Actuation Set               Contact       Contact
Mark Warhead                18-2          18-2
Serial Number               3668          3128
Explosive                   Torpex        Torpex
Firing interval             0             8 S
Spread                      125 Forward   125 Aft.
Sea Condition               2             2
Overhaul Activity           U.S.S. APOLLO (AS25)

REMARKS: Injection temperature used 60°F. Battery temperature
         used for speed correction was 60°F.

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ENCLOSURE (A)

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U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
---

(H) ATTACK DATA:
---

U.S.S. SENNET

TORPEDO ATTACK NO. 3.
PATROL NO. 3.

Time
----
0747 (K)

Date
----
28 April 1945

Lat.
----
33 - 58 N.

Long.
-----
136 - 17 E.

TARGET DATA

DESCRIPTION: CABLE LAYER.

Target Draft

12 Ft.

Course
------
213

Speed
-----
0

Range
-----
2,900 for #7.
3,300 for #8 & #9.

OWN SHIP DATA

Speed
-----
2 ¼

Course
------
102

Depth
-----
60 Ft.

Angle (at firing)
-----
0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

REMARKS: These torpedoes were fired in an attempt to hasten the sinking
         of ship in #2 attack.

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ENCLOSURE (..)

— page 83 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA (Continued).

Tubes Fired                 7          8          9
Track Angle                 111 P      111 P      111 P
Gyro Angle                  180        180        180
Depth Set                   4          6          6
Power                       High       High       High
Hit or Miss                 Miss       Miss       Miss
Erratic                     No         No         No
Mark Torpedo                23         23         23
Serial                      65830      50273      63404
Mark Exploder               6-5        6-5        6-5
Serial Number               14056      25896      25006
Actuation Set               -          -          -
Mark Warhead                16-1       16-1       16-1
Serial Number               20893      1364       16691
Explosive                   Torpex     Torpex     Torpex
Firing interval             0          -          10 S
Spread                      None       10 yd. R.  10 yd. L.
Sea Condition               2          2          2
Overhaul Activity           U.S.S. APOLLO (AS25)

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ENCLOSURE (A)

— page 84 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

(H) ATTACK DATA:

U.S.S. SENNET

Time
0831 (K)

TORPEDO ATTACK NO. 4. PATROL NO. 3.

Date Lat. Long.
1 May 1945 33 - 28 N. 135 - 32 E.

TARGET DATA

DESCRIPTION: ASASHIO CLASS DESTROYER. 2,000 Tons.

Ship's / Sunk: NONE

Ship's / Damaged
or probable sunk: NONE

Target Draft Course Speed Range
12 Ft. 295 12 2000

OWN SHIP DATA

Speed Course Depth Angle (at firing)
6 03543 60 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

Misses are believed to be a result of enemy turning tail upon
sighting wake of first torpedo and evading all shots.

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ENCLOSURE (A)

— page 85 —
(A) [UNCLEAR: TRUCULURE]
                                                              U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued).

Tubes fired                               1             2             4             5             6
Track Angle                             117 P         119 P         120 P         124 P         127 P
Gyro Angle                              323[HANDWRITTEN: 40]        321[HANDWRITTEN: 30]        320           316           313[HANDWRITTEN: 50]
Depth Set                                 4             4             4             4             4
Power                                   High          High          High          High          High
Hit or Miss                             Miss          Miss          Miss          Miss          Miss
Erratic                                   -             -             -             -             -
Mark: Torpedo                             23            23            23            23            23
Serial (A) [UNCLEAR: TRUCULURE]         65404         62970         49749         46137         65271
Mark Exploder                           6-5           6-5           6-5           6-5           6-5
Serial Number                           13999         25045         14775         17302         26090
Actuation Set                           Contact       Contact       Contact       Contact       Contact
Mark Warhead                            16-1          16-1          16-1          16-1          16-1
Serial Number                           20938         12043         12312         12270         5823
Explosive                               Torpex        Torpex        Torpex        Torpex        Torpex
Firing interval                           6             7             12            14            11
Spread                                  Periscope     Periscope     Periscope     Periscope     Periscope
Sea Condition                             2             2             2             2             2
Overhaul Activity                       U.S.S. APOLLO (AS25)

                                                                - 21 -

                                                                                ENCLOSURE (A)

— page 86 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

(I) MINES:

     Several floating mines were encountered. One (1) was destroyed by a
direct hit with a 40 MM. Ten (10) previous hits with small arms were in-
effective.

(J) ANTI-SUBMARINE MEASURES AND EVASION TACTICS:

     Strafed by aircraft on a pitch black night. Believe his search radar
was above the frequency detection range of the APR equipment.

     Attack with torpedoes twice by what is believed to have been an anti-
submarine "PT" boat squadron.

     Low frequency pinging gear was the standard equipment on patrol boats
in this area.

     Our evasion tactics were running slow at deep submergence away from the
coast. The fathomoter was used after each depth charge until the 100 fathom
curve was reached. A frequency modulated fathomometer would be a boon for use
on occasions like this.

(K) MAJOR DEFECTS AND DAMAGE:

     None.

(L) RADIO:

     The antenna trunk continued to flood at deep depths although several
attempts have been made during refit periods to remedy this situation. The
trouble has existed since the ship was placed in commission.

     The whip antenna, which was reportedly a jury rig when it was first
installed by the Submarine Base, Pearl Harbor, needs complete overhaul. The
coil spring has lost all its tension and the hold-down ratchets are out of
line. As a result, the tip of the antenna breaks the water at 56 feet.

     No serious difficulty was encountered transmitting messages, and no
ComSubPac serials were missed.

     Most satisfactory frequency used for transmission at night was 4155,
while 8470 was found excellent for daylight transmissions.

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ENCLOSURE (A)

— page 89 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(S) DURATION:

    Days enroute to area        4
    Days in area               25
    Days enroute to base       16
    Days submerged             23

(T) FACTORS OF ENDURANCE REMAINING:

    Torpedoes           Fuel              Provisions      Personnel Factor

    2                   12,000 gallons    30 days         10 days

    Limiting factors this patrol - Fuel and Torpedoes.

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES:

    RADAR COUNTERMEASURES:

        APR

        While patrolling the area off KII SUIDO, many land based radars were
        picked up on the APR. The following tables list these radars according to
        their general locations:

        SOUTH AND SOUTHWEST OF SHIONO MISHA

        FREQUENCY       PRF       PULSE WIDTH
        150             500       3
        100             500       20
        147             500       5
        152             500       5
        82              500       30
        300             500       15
        154             500       3
        108             500       10
        99              500       18
        150             500       12

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C-O-N-F-I-D-E-N-T-I-A-L

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES (Continued):

RADAR COUNTERMEASURES (Continued):

APR Continued:

FREQUENCY | PRF                 | PULSE WIDTH
||
          | EAST OF ASHIZURI SAKI |
150       | 500                 | 8
156       | 500                 | 10
136       | 500                 | 10
157       | 500                 | 10
158       | 500                 | 3
98        | 800                 | 20
          | WEST OF MUROTO ZAKI |
100       | 900                 | 4
98        | 900                 | 30
137       | 500                 | 20
150       | 500                 | 8
151       | 500                 | 20
98        | 500                 | 18
82        | 500                 | 20
153       | 500                 | 5
146       | 500                 | 5

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ENCLOSURE (A)

— page 91 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES (Continued):

RADAR COUNTERMEASURES (Continued):

APR Continued:

                                                                KANTORI ZAKI

FREQUENCY                               PRF                     PULSE WIDTH
157                                     500                     18
299                                     500                     12
154                                     500                     3-4
98                                      500                     15
100                                     500                     18
208                                     500                     5
82                                      500                     -

SD-4 RADAR:

        During the first three days in the area we had interference on the SD
which caused the sweep to jump up and down. When we were closest to ASHIZURI
the interference seemed to be the strongest. However if it was some type of
jamming it was not very effective. On 27 April 1945 the SD was jammed by
what seemed to be noise modulated C.W. This jamming occurred at Lat. 33-30 N.
Long. 136-45 E. but only lasted 20 minutes.

SJ-1 RADAR:

        Ten centimeter radar interference was encountered on several occasions
when it was known that none of our submarines were in the vicinity. Am
convinced that the "PT" boats encountered on 16 April 1945 were using this
equipment.

COMMUNICATIONS COUNTERMEASURES:

        Very little jamming was experienced. No unusual difficulties in
receiving or transmitting were encountered.

SONAR COUNTERMEASURES:

        None.

                                        - 27 -

                                                                ENCLOSURE (A)

— page 92 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(V) REMARKS:

An APR receiver covering frequencies up to 3500 Mcs. should be a
"MUST PRIORITY" for all operating submarines.

A Photographers Mate was assigned to the ship for this patrol. He
was told to attempt to get pictures of expressions on the faces of
personnel during depth charge attack.

RESULTS: No pictures.

HIS REASONS: 1. The camera made too much noise.

2. He was too busy.

- 28 -

ENCLOSURE (A)

— page 93 —
FB5-102/A16-3
Serial 012
CONFIDENTIAL
FIRST ENDORSEMENT
to CO SENNET Conf. Ltr.
SS408/A16-3 Ser. 05-45
dated 16 May, 1945.

SUBMARINE DIVISION 102
Care of Fleet Post Office,
San Francisco, California,
18 May, 1945.

From: The Commander Submarine Division ONE HUNDRED TWO.
To : The Commander-in-Chief, United States Fleet.
Via : (1) The Commander Submarine Squadron TEN.
(2) The Commander Submarine Force, Pacific Fleet.
(3) The Commander-in-Chief, Pacific Fleet.

Subject: U.S.S. SENNET - Report of War Patrol Number THREE.

1. The third war patrol of the U.S.S. SENNET was conducted in the
area of KII SUIDO. The patrol covered a period of 45 days of which 25 were
spent in the area.

2. The area was well covered and every opportunity was taken to
inflict damage on the enemy by this experienced and capable commanding officer.

ATTACK NO. 1.
On April 19, a submerged attack was made on a medium AK similar to the
KIIISHIMA MARU, which was escorted by 1 large and 4 small escorts and 1 Sugar
Dog. Three Mk 18 torpedoes were fired, one of which was seen to hit amid-
ships. The target was seen to list to starboard with decks awash, and bow
and stern were elevated in such a manner to indicate that the ship's back was
broken. Although the target was not seen to sink, there is every indication
that it did so.

ATTACK NO. 2.
Initial contact on 28 April, was by sound detecting enemy pinging. Target
appeared to be a Naval Cable Layer. Two Mk. 18 torpedoes were fired with
excellent results. The first blew the bow off and the second hit under the
mainmast. As the ship was down by the stern but not sinking, a third torpedo
was fired. This torpedo missed. Seven minutes later two more torpedoes were
fired at a range of 3200 yards. Those torpedoes also missed. The ship was
seen to sink approximately one hour after hits were made.

ATTACK NO. 3.
This attack was made on 1 May, initial contact being made by sound picking
up echo ranging. Target was an ASHIO Class Destroyer. Five Mk. 23 torpedoes
were fired with a good fire control set-up. All torpedoes missed because of
maneuvering of target. Following this attack the SENNET was forced to take
evasive measures due to the presence of three patrol vessels who dropped depth
charges for two hours but fortunately none were close.

- 1 -

— page 94 —
FB5-102/A16-3

Serial 012

CONFIDENTI.L

FIRST ENDORSEMENT to
CO SENNET Conf. ltr.
SS408/A16-3 Ser. 05-45
dated 16 May, 1945.

Subject: U.S.S. SENNET - Report of War Patrol Number THREE.

— page 95 —
FF12-10(A)/A16-3(18) SUBMARINE FORCE, PACIFIC FLEET
Serial: 01283

CONFIDENTIAL
THIRD ENDORSEMENT to
SENNET Report of
Third War Patrol.

COMSUBSPAC PATROL REPORT NO. 767
U.S.S. SENNET - THIRD WAR PATROL.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander in Chief, United States Fleet.
Via : The Commander in Chief, U.S. Pacific Fleet.
Subject: U.S.S. SENNET (SS408) - Report of Third War Patrol
(3 April to 16 May 1945).

1. The third war patrol of the SENNET, under the command
of Commander G. E. Porter, U.S. Navy, was conducted in the areas off
Kii Suido. In addition to offensive patrol, life guard services were
rendered.

2. This extremely well conducted patrol close to the
enemy coast produced worthwhile contacts. Four attacks were made.
During these well executed attacks the SENNET sank a freighter and
a naval cable layer. One attack on an ASASHIO class destroyer was
unsuccessful when the enemy sighted torpedo wakes and evaded success-
fully. Area coverage was thorough and attacks aggressively conduc-
ted.

3. Award of Submarine Combat Insignia for this patrol is
authorized.

4. The Commander Submarine Force, Pacific Fleet, congra-
tulates the commanding officer, officers, and crew for the comple-
tion of this successful aggressive patrol. The SENNET is credited
with having inflicted the following damage upon the enemy:

SUNK
1 - AK (similar to KIMISIMA MARU)(EC) - 5,193 tons (Attack No. 1)
1 - Naval Cable Layer (EU) - 3,000 tons (Attack No. 2)
1 - Escort Vessel (Catcher Type)(EU) - 500 tons*
TOTAL SUNK 8,693 tons

* Covered by separate report.

Distribution and authentication
on following page.

1d
Care of Fleet Post Office,
San Francisco, California,
30 May 1945.

NOTE: THIS REPORT WILL BE
DESTROYED PRIOR TO
ENTERING PATROL AREA.

MERRILL COMSTOCK.
- 1 -

— page 96 —
1d
FF12-10(A)/416-3(18) SUBMARINE FORCE, PACIFIC FLEET
Serial: 01283

Care of Fleet Post Office,
San Francisco, California,
30 May 1945.

CONFIDENTIAL
THIRD ENDORSEMENT to
SENNET Report of
Third War Patrol.

NOTE: THIS REPORT WILL BE
DESTROYED PRIOR TO
ENTERING PATROL AREA.

COMSUBSPAC PATROL REPORT NO. 767
U.S.S. SENNET - THIRD WAR PATROL.

Subject: U.S.S. SENNET (SS408) - Report of Third War Patrol
(3 April to 16 May 1945).

DISTRIBUTION:
(Complete Reports)
Cominch (7)
CNO (5)
Cincpac (6)
JICPOA (1)
AdICPOA (1)
Comservpac (1)
Cinclant (1)
Comsubslant (8)
S/M School, NL (2)
CO, S/M Base, PH (1)
Comsopac (2)
Comsowespac (1)
Comsubsowespac (2)
CTG 71.5 (2)
Comnorpac (1)
Comsubspac (3)
ComsubspacAdComd (40)
SUBAD, MI (2)
ComsubspacSubordcom (3)
All Squadron and Div.
Commanders, Pacific (2)
SubTrainPac (2)
All Submarines, Pacific (1)

[SIGNATURE: E. L. Hynes] [HANDWRITTEN: use and]
E. L. HYNES, 2nd.,
Flag Secretary.

— page 97 —
[STAMP: PROCESSED COPY]
[HANDWRITTEN: 3]
U.S.S. SENNET (SS408)

SS408/A16-3
Serial: 0002-45

[STAMP: DECLASSIFIED]
CONFIDENTIAL - DOD DIR. 5200.9
BY [HANDWRITTEN: J.J. Kerr] DATE [HANDWRITTEN: 4-16-60]

Care of Fleet Post Office,
San Francisco, California.
16 May 1945

From: The Commanding Officer.
To: The Commander-in-Chief, United States Fleet.
Via: (1) The Commander Submarine Division 102.
     (2) The Commander Submarine Squadron 10.
     (3) The Commander Submarine Force, Pacific Fleet.
     (4) The Commander-in-Chief, U. S. Pacific Fleet.

Subject: U.S.S. SENNET, Top Secret Report of Firing Mark 27
         Torpedoes, Patrol No. THREE.

Enclosure: (A) Subject Report.

1. Enclosure (A) is forwarded herewith.

[SIGNATURE: G. E. FORTER]
G. E. FORTER.

— page 98 —
U.S.S. SENNET (SS408)

T-O-P S-E-C-R-E-T

MARK 27 TORPEDO ATTACK

U.S.S. SENNET Mark 27 Torpedo Attack No. 1. Patrol No. 3.

Time Date Lat. Long.
0957 (K) 13 April 1945 33 - 21 N. 133 - 44 E.

Sound Conditions: GOOD Depth of Water: 55 FATHOMS
Distance to nearest shore or reef: 8 MILES. Sea Condition: CALM
Was it raining? No.

TARGET DATA - DAMAGE INFLICTED

Description: Single Ship, Sea Truck. 500 Tons.

Ship Sunk: NONE
Ship Damaged: NONE
Damage deter-
mined by:

Target draft Course Speed Range
4 Feet 137 5 250

Target turn count: NOT TAKEN Target bearing: 148

Peculiarities in target's sound output: NONE.

- 1 -

ENCLOSURE (A)

— page 99 —
U.S.S. SENNET. (SS408)

T-O-P S-E-C-R-E-T

MARK 27 TORPEDO ATTACK (Continued).

OWN SHIP DATA

Speed             Course             Depth             Angle (at firing)
2.5               256                160 Feet          0

FIRE CONTROL & TORPEDO DATA

Was target aware of submarine's presence?          No.

Was submarine being depth charged?                 No.

Type Attack:      JP was out of commission. Firing point determined by TDC
                  range and JK sound gear.

Tube fired from:  10                                 Erratic:          UNKNOWN

Hit or Miss:      MISS                               Serial No:        460

Aiming distance set: 100 yds.

Issuing activity: U.S.S. PROTEUS (AS11)

Comments:         Torpedo fired from a position ahead of target. Target passed
                  close aboard.

- 2 -

ENCLOSURE (A)

— page 100 —
T-O-P S-E-C-R-E-T
U.S.S. SENNET (SS408)
Patrol No. 3.

MARK 27 TORPEDO ATTACK

U.S.S. SENNET
Mark 27 Torpedo Attack No. 2.

Time                 Date                 Lat.                 Long.
1122 (K)             14 April 1945        33 - 23 N.           133 - 49 E.

Sound Conditions: GOOD                     Depth of Water: 55 FATHOMS
Distance to nearest shore or reef: 7 MILES. Sea Condition: CALM
Was it raining? No.

TARGET DATA - DAMAGE INFLICTED

Description: Single Ship, Sea Truck. 300 Tons.
Ship Sunk: NONE
Ship Damaged: NONE
Damage deter-
mined by:

Target draft         Course               Speed                Range
4 Feet               130                  5.5                  520

Target turn count: NOT TAKEN               Target bearing: 210

Peculiarities in target's sound output: NONE.

- 3 -

ENCLOSURE (A)

— page 101 —
U.S.S. SENNET (SS408)

T-O-P S-E-C-R-E-T

MARK 27 TORPEDO ATTACK (Continued).

                                                              OWN SHIP DATA

Speed                               Course                  Depth                   Angle (at firing)
2.0                                 214                     160 Feet                0

                                                      FIRE CONTROL & TORPEDO DATA

Is target aware of submarine's presence?              No.

Is submarine being depth charged?                     No.

Type attack:          JP was out of commission. Firing point determined by TDC
                      range and JK sound gear.

No. fired from:       10                                    Erratic:                UNKNOWN

Hit or Miss:          MISS                                  Serial No:              592

Running distance set: 100 yds.

Escort activity:      U.S.S. PROTEUS (AS11)

Remarks:              Torpedo fired from a position ahead of target. Target passed close
                      aboard.

                                                              - 4 -

                                                              ENCLOSURE (A)

— page 102 —
T-O-P S-E-C-R-E-T
U.S.S. SENNET (SS408)

MARK 27 TORPEDO ATTACK
Mark 27 Torpedo Attack No. 3 Patrol No. 3.

Time Date Lat. Long.
0538 (K) 19 April 1945 33 - 35 N. 135 - 23 E.

Sound Conditions: GOOD Depth of Water: 250 Feet.
Distance to nearest shore or reef: 4,000 yds. Sea Conditions: Force 2.
Is it raining: No.

TARGET DATA - DAMAGE INFLICTED

Description: UNKNOWN (One of five escort vessels). (Four of the escort
vessels were small CATCHER type of about 500 Tons. One was
a large "PC" boat of about 1,000 Tons).

Ship Sunk: UNKNOWN
Ship Damaged: UNKNOWN
Damage Deter-
mined by: 4 minutes 40 seconds after firing an explosion occurred. This
explosion was undoubtedly a Mark 27 torpedo explosion, as it
is distinctive in that it sounds like the crack of a gun and
is easily distinguished from a depth charge. The screws of the
nearest escort vessel were immediately silenced.

Course Speed Range
UNKNOWN UNKNOWN CLOSE ABOARD

Target turn count: NOT TAKEN Target bearing: 292°T.

Peculiarities in target's sound output: NONE.

- 5 -
ENCLOSURE (A)

— page 103 —
T-O-P S-E-C-R-E-T                                                              U.S.S. SENNET (SS408)

MARK 27 TORPEDO ATTACK (Continued).

                                                                                             OWN SHIP DATA

Speed                                 Course                                  Depth                                 Angle (at firing)
2.0                                   260°T.                                  200 Feet                              5 D

                                                                                FIRE CONTROL & TORPEDO DATA

Was target aware of submarine's presence:                                       Yes.

Was submarine being depth charged:                                              Yes.

Tube fired from:                      10                                      Erratic:                              No.

Hit or Miss:                          HIT                                     Time from firing to hit:              4M40S

MK. Torpedo:                          27                                      Serial:                               315

Arming distance set:                  100 yds.

Issuing activity:                     U.S.S. PROTEUS (AS11)

Comments:                             This attack was delivered as a counter measure to a group of
                                      anti submarine escort vessels attacking us. Ship was going
                                      deep after a successful torpedo attack.

                                                                                - 6 -

                                                                                                                            ENCLOSURE (A)

— page 104 —
T-O-P S-E-C-R-E-T
U.S.S. SENNET (SS408)

MARK 27 TORPEDO ATTACK

Mark 27 Torpedo Attack No. 4. Patrol No. 3.

Time Date Lat. Long.
0846 (K) 1 May 1945 33 - 58 N. 136 - 17 E.

Sound Conditions: GOOD Depth of Water: 65 FATHOMS
Distance to nearest shore or reef: 4,800 yds. Sea Condition: Force 2
Was it raining? No.

TARGET DATA - DAMAGE INFLICTED

Description: ASASHIO CLASS DESTROYER. 2,000 Tons.

Ship Sunk: NONE

Ship Damaged: NONE

Target Draft Course Speed Range
12 Feet - - -

Target turn count: NOT TAKEN Target bearing: 180

Peculiarities in target's sound output: NONE.

- 7 -

ENCLOSURE (A)

— page 105 —
U.S.S. SENNET (SS408)
T-O-P S-E-C-R-E-T

MARK 27 TORPEDO ATTACK (Continued).

OWN SHIP DATA

Speed             Course             Depth             Angle (at firing)
2.5               160                400 Ft.           3 D

FIRE CONTROL & TORPEDO DATA

Was target aware of submarine's presence?        Yes.
Was submarine being depth charged?               Yes.
Type Attack:      See Comment.

Tube fired from:  9                  Erratic:          UNKNOWN

Hit or Miss:      MISS               Serial No:        749 T

Arming distance set: 100 yds.

Issuing activity: U.S.S. PROTEUS (AS11)

Comments:         This attack from deep submergence was made as a defensive
                  measure against an ASW SHIP CLASS DESTROYER, who having dodged
                  five (5) of our torpedoes, was about to work us over.

- 8 -

ENCLOSURE (A)

— page 106 —
[STAMP: SECRET]
FF12-10(A)/A16-3/S75
Serial, 00039
[STAMP: TOP SECRET]

[HANDWRITTEN: d.m. 06609]
SUBMARINE FORCE, PACIFIC FLEET

Ga.
[HANDWRITTEN: 01967]
Care of Fleet Post Office,
San Francisco, California,
28 May 1945.

[HANDWRITTEN: 6-167]

THIRD ENDORSEMENT to
CO USS SENNET Top Secret ltr
file SS408/A16-3 Serial 002-45
dated 16 May 1945.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander in Chief, United States Fleet.
Via : The Commander in Chief, U. S. Pacific Fleet.

Subject: U.S.S. SENNET (SS408) - Top Secret Report of Firing Mark 27
Torpedoes, War Patrol No. 3.

1. Forwarded.

2. It is believed there is sufficient evidence to assess sinking of
a patrol vessel in the third attack.

3. The Commander Submarine Force, Pacific Fleet, congratulates the
commanding officer, officers, and crew of the SENNET for this successful attack
with this valuable new weapon. Damage assessed has been added to the Force
Commander's endorsement to the SENNET's third war patrol report.

MERRILL COMSTOCK.

DISTRIBUTION:
Cominch (2)
CNO (2)
Cincpac (3)
Comsubspac (2)
ComsubspacAdComd (2)
ComsubsTrainpac (2)
Comsubsland (2)
Comsubs7thFleet (2)
All Squadron Commanders (1)
All Division Commanders (1)
BuOrd (2)
BuShips (2)
CO USS SENNET (1 copy this
endorsement only).

A16-3/ss
000573

3 JUN 1945

[HANDWRITTEN: 4th Endorsement]
[HANDWRITTEN: Cinc Pacific Fleet]
To: [HANDWRITTEN: Cominch]
Via:

1. Forwarded.
[SIGNATURE: R. E. Keeton]
R. E. KEETON
By Direction

[SIGNATURE: E. L. Hynes]
E. L. HYNES, 2nd
Flag Secretary.

[STAMP: SECRET]

— page 107 —
SUBMARINE DIVISION 102

F15-102/A16-3                                      Care of Fleet Post Office,
Serial 0001                                        San Francisco, California,
                                                   18 May, 1945.
T-O-P S-E-C-R-E-T

FIRST ENDORSEMENT to
CO SUBRON TEN Top Secret ltr.
SS408/A16-3 Serial 0002-45
dated 16 May, 1945.

From:      The Commander Submarine Division ONE HUNDRED TWO.
To :       The Commander-in-Chief, United States Fleet.
Via :      (1) The Commander Submarine Squadron TEN.
           (2) The Commander Submarine Force, Pacific Fleet.
           (3) The Commander-in-Chief, Pacific Fleet.

Subject:   U.S.S. SENNET, Top Secret Report of Firing Mark 27
           Torpedoes, Patrol Number THREE.

1.         Forwarded.

                                                   [SIGNATURE: J. P. THIEL]
                                                   J. P. THIEL

SECOND ENDORSEMENT                                 SUBMARINE SQUADRON TEN
FC5-10/A16-3
                                                   Care of Fleet Post Office,
Serial: 0001                                       San Francisco, California,
                                                   18 May 1945.
T-O-P S-E-C-R-E-T

From:      The Commander Submarine Squadron Ten.
To :       The Commander-in-Chief, United States Fleet.
Via :      (1) The Commander Submarine Force, Pacific Fleet.
           (2) The Commander-in-Chief, Pacific Fleet.

1.         Forwarded.

                                                   [SIGNATURE: J. P. THIEL]
                                                   J. P. THIEL

— page 108 —
SS408/A16-3
Serial: 07-45.

U.S.S. SENNET (SS408)

Care of Fleet Post Office,
San Francisco, California.

9 August 1945.

C-O-N-F-I-D-E-N-T-I-A-L [STAMP: DECLASSIFIED]
[STAMP: DECLASSIFIED ART. 0445 OPNAVINST 5510.1C]
BY [HANDWRITTEN: OPOBA] DATE [HANDWRITTEN: 9/16/7]

From: The Commanding Officer.
To: The Commander-in-Chief, United States Fleet.
Via: (1) The Commander Submarine Division
     (2) The Commander Submarine Squadron
     (3) The Commander Submarine Force, Pacific Fleet.
     (4) The Commander-in-Chief, U. S. Pacific Fleet.

Subject: U.S.S. SENNET - Report of War Patrol Number FOUR.

Enclosure: (A) Subject Report.

1. Enclosure (A), covering the Fourth War Patrol of this
vessel conducted in the SEA OF JAPAN during the period from 1 July
1945 to 9 August 1945, is forwarded herewith.

[SIGNATURE: C. R. CLARK.]

[STAMP: FILMED]
[STAMP: 138091]

— page 109 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

(A) PROLOGUE:

    Arrived Pearl on 16 May 1945 from THIRD WAR PATROL and moored alongside
    U.S.S. SPERRY. Refit was accomplished by Submarine Division ONE HUNDRED TWO.

    On 26 May Lieutenant D. R. JONES, U.S. Navy, Lieutenant (jg) T. P. DORR,
    U.S. Navy, Lieutenant (jg) T. A. EHRISMAN, U.S.N.R., Ensign J. T. SEAGO, U.S.
    Navy, and Ensign P. B. PIKE, U.S. Navy reported aboard for duty.

    On 27 May SENNET was shifted to Submarine Division ONE HUNDRED TWO at the
    Submarine Base for installation of special gear.

    On 31 May Lieutenant Commander C. R. CLARK, jr., U.S. Navy relieved
    Commander G. E. PORTER, jr., U.S. Navy as Commanding Officer. Lieutenant J.
    D. ROCHE, U.S.N.R., Lieutenant (jg) "C" "B" KOSSERT, U.S. Navy, Lieutenant
    (jg) V. E. BURKS, U.S. Navy, and Ensign E. V. ANDERSON, U.S. Navy were
    detached.

    The following new gear was installed during refit period: APR-5, SD-5
    receiver, and TDM (minus the streamlined dome).

    An excellent refit was given by the U.S.S. SPERRY and the Submarine
    Base, Pearl Harbor, T.H.

    Conducted TEN (10) days of normal training and FOUR (4) days of special
    training. Topped off stores and fuel, loaded torpedoes, and on 1 July
    departed on patrol.

    During the refit period, the following transfers were effected:

    DETACHED: FIVE (5) Officers.
    REPORTED: FIVE (5) Officers.
    TRANSFERRED: TWENTY-FOUR (24) Enlisted Men.
    RECEIVED: TWENTY-FIVE (25) Enlisted Men.

    The following officers are on board:

    NAME                                | PREVIOUS WAR PATROLS
    Lieut-Comdr., Charles R. CLARK, jr. | TWO (2) DACE
                                        | THREE (3) SENNET
    Lieut., Frank A. ANDREWS            | THREE (3) SENNET

- 1 -

ENCLOSURE (A)

— page 110 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408)

(A) PROLOGUE (Continued):

Lieut., Donald R. JONES                               NONE
Lieut.(jg), Theodore P. DORR                           SEVEN         (7) PORPOISE
Lieut.(jg), John H. VAN NESS                           THREE         (3) SENNET
Lieut.(jg), Thomas A. EHRISMAN                         NONE
Lieut.(jg), Donnel H. WAGNER                           THREE         (3) SENNET
Lieut.(jg), George H. SWANSON                          ONE           (1) SENNET
Ensign, James T. SEAGO                                 FOUR          (4) S-14
Ensign, Percy B. PIKE                                  TWO           (2) PAMPANITO
Mach., Anthony KARETNUK                                NINE          (9) SWORDFISH
                                                       THREE         (3) SENNET

The following CPO's are on board during this patrol:

NAME                                   RATE            PREVIOUS WAR PATROLS
R. ILLY, Tex D.,                       CTM(AA)(T)      FIVE          (5) POGY
                                                       THREE         (3) SENNET
SHELLMAN, Curtis B.,                   CQM(T)          NONE
WILSON, William A.,                    CRT(AA)(T)      FIVE          (5) TINOSA
                                                       THREE         (3) SENNET
HALL, Leon W.,                         CMOMM(T)        FOUR          (4) S-45
                                                       THREE         (3) SENNET
COGHILL, Kettig S.,                    CMOMM(T)        ONE           (1) BALAO
                                                       TWO           (2) SENNET
STEPHENSON, Russel O.,                 CMOMM(AA)(T)    SIX           (6) BLACKFISH
                                                       THREE         (3) SENNET
BRENGELMAN, Henry B.,                  CEM(PA)         EIGHT         (8) SEAWOLF
                                                       ONE           (1) SARGO
                                                       THREE         (3) SENNET

- 2 -

ENCLOSURE (A)

— page 111 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(B) NARRATIVE:

1 July 1945.
     1400 Underway from PEARL HARBOR enroute GUAM in accordance with CTF 17
          operation order #126-45.

2 July 1945 to 12 July 1945.
          Conducted routine training enroute.

13 July 1945.
     1200 Entered APRA HARBOR. Moored alongside U.S.S. SPERRY for voyage
          repairs.

14 & 15 July 1945.
          Conducted special training exercises.
          Torpedoman J. M. GETTLE, U.S. Navy was detached.
          Ensign G. H. SWANSON, U.S.N.R. reported aboard.

16 July 1945.
          Loaded.

17 July 1945.
          Underway from GUAM in company with U.S.S. FOOY for patrol in
          accordance with CTF 17 operation order #163-45.

THE PERIOD 18 JULY TO 27 JULY IS COVERED IN A SPECIAL REPORT.

27 July 1945.
          All times will be ITEM (-10).
     2000 Arrived on station. Lat. 40 - 46 N. Long. 139 - 40 E.
          Commenced patrolling off HEMASHI SAKI.
     2250 SJ Contact Bearing 130°T. Range 14,000 yds. (Ship Contact #1).
          The target was less than two thousand yards off the beach and had
          almost gotten by us when we detected it. Commenced end around.

                                   - 3 -

                                                            ENCLOSURE (A)

— page 112 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

28 July 1945.
1200 Position: Lat. 39 - 59 N. Long. 139 - 15 E.

0022 Three (3) more SJ Contacts Bearing 200°T. Range 23,000 yds.
     (Ship Contacts #2, 3, and 4).
     Had to make choice of single sure target or several in the bush.
     Took the one in hand.
0111 Commenced firing five (5) torpedoes at LARGE AK (silhouette similar
     to page 99 ONI 208-J). Range 2,200 yds. Track 103 S. Spread 100
     feet between torpedoes. Was stopped and trimmed down to get best
     performance out of the torpedoes. (Attack #1).
0113 Observed three (3) hits. His stern was blown off and he immediately
     sank until his decks were awash. He started shooting at random
     with automatic weapons. Commenced chasing other targets now at
     18,000 yds. very much alerted and headed for FUNAKAWA WAN.
0118 First target stopped shooting.
0122 Suddenly lost good pip on SJ Radar on ship we had hit. Range 7000
     yds. Target not in sight believe he sank.
0319 Submerged ahead of new targets in bright moonlight. Closing SHIOSE
     Saki at SJ radar depth; had to close beach to 2,000 yds.
0340 Could see all targets. One (1) SMALL AK (similar bottom page 151
     ONI 208J) followed by two (2) LARGE AK's engine aft. (Two goal
     posts, mast and stack, estimated about 5,000 tons).
0355 Decided to shoot at the two (2) big ones and let the little one go.
     One of the big ones zigged away from the beach and gave us a stern
     shot, with two (2) nice bow tube shots on the others.
0405 Commenced firing three (3) torpedoes at the inboard LARGE AK.
     Range 1,800 yds. Track 37 S. (Attack #2).
0406 Fired three (3) torpedoes at the SMALL AK. Range 800 yds. Track
     123 S. (Attack #3).
0407 Fired three (3) torpedoes at the LARGE AK aft of us. Range 1,400
     yds. Track 110 P. (Attack #4).
     Saw one (1) hit in the small AK. He started down immediately.
     The AK shot at first had now seen his fish and paralleled them.
     Saw two (2) hits in the AK aft of us. His bow was blown off and
     he started to sink.
0409 It was now almost daylight and the AK that we missed saw our scope
     that had been up for about thirty minutes, and headed for it.
     Went deep (150 ft.).
0411 Received one (1) depth charge at 150 ft.
0414 Received another depth charge.
0425 Periscope depth. Saw two (2) groups of lifeboats, survivors and
     debris and the intact AK heading away fast. He was as worried
     about the survivors as we were. (They had no real complaint, they
     were less than a mile from the beach).
0430 Cleared area submerged.
1618 Surfaced. Headed for MOTSUTA MISAKI.

- 4 -
ENCLOSURE (A)

— page 113 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408).

29 July 1945. 1200 Position: Lat. 42 - 35 N. Long. 139 - 48 E.

0305 Sighted HOTSUTA MISAKI light showing normal characteristics.
0335 Submerged for close in patrol off HOTSUTA MISAKI.
0355 Sighted ship bearing 043°T. (Ship Contact #5).

SEE SEPARATE REPORT.

2008 Surfaced. Patrolled at slow speed trimmed down seven (7) miles
off beach. Used SJ continuously. Did not use SD.

30 July 1945. 1200 Position: Lat. 42 - 35 N. Long. 139 - 48 E.

0337 Submerged to conduct close in patrol off MOTSUTA MISAKI.
0902 Sighted ship bearing 160°T. Range 12,000 yds. (Ship Contact #6).
0942 Fired three (3) torpedoes at LARGE AK. Range 1,650 yds. Track
103 P. Spread by periscope. Commenced taking pictures thru #2
periscope. (Attack #5).
0943 Saw two (2) torpedoes hit in target. He began to sink immediately
and list to port.
0945 The target had been turned 90° from his track by the torpedoes and
shows a very wide beam.
0954 Target was laying over on its side and about 100 Japs were now on
the side of the ship and were hastily jumping off into the water.
0955 Very good pictures were taken of entire action.
1857 Target sank. Cleared area.
2300 Surfaced. Headed North to patrol off KAMOI MISAKI.
2320 Commenced patrolling trimmed down six (6) miles off beach.
SJ Contact bearing 095°T. Range 12,500 yds. Commenced tracking
two (2) targets heading South along coast. (Ship Contacts #7 & 8).

31 July 1945.

0031 Headed in for attack. Targets were against shore background and
could not be made out until the range had closed to about 3,500 yds.
Then it was seen that they were two (2) PC boats. They had been
steaming down the coast at eight (8) knots with merchant ship type
maneuvers. (Some kind of a beartrap). It was too late to change
now.
0051 Fired two (2) Mk 14 torpedoes fwd, range 2,600 yds. track 110 S.
one (1) Mk 18 aft and cleared the area. All torpedoes missed
and targets were not alerted. (Attack #6).
0118 Picked up possible 10 CM interference as we were moving out.
0330 Headed for GUAM.

REMAINDER OF PATROL REPORT IS COVERED IN A SPECIAL REPORT.

- 5 -

ENCLOSURE (A)

— page 114 —
C-O-N-F-I-D-E-N-T-I-A-L

U.S.S. SENNET (SS408);

(C) WEATHER:
    In general very foggy and overcast with force 1 to 2 seas, and force 2
    winds usual.

(D) TIDAL INFORMATION:
    NONE.

(E) NAVIGATIONAL AIDS:
    MOTSUTA MISAKI light was in operation Lat. 42 - 37 N. Long. 139 - 51 E.

(F) SHIP CONTACTS:
No. | Time | Lat. Long. | Type(s)      | Initial Range | Est.Course & Speed | How Con-tacted? | Remarks
----|------||||||
1   | 7-27 | 40-35 N    | LARGE AK     | 14,000        | 180                | SJ Radar        | Attack #1 (Sunk)
    | 2250 | 139-50 E   |              |               | 8                  |                 |
2   | 7-28 | 40-20 N    | LARGE SA     | 23,000        | 180                | SJ Radar        | Attack #2
3   | 0022 | 139-50 E   | LARGE SA     |               | 7                  |                 | Attack #3 (Sunk)
4   |      |            | SMALL AK     |               |                    |                 | Attack #4 (Sunk)
5   | 7-29 | 42-37 N    | SMALL AK     | 10,000        | 180                | Periscope       | -----
    | 0355 | 139-50 E   |              |               | 8                  |                 |
6   | 7-30 | 42-35 N    | LARGE AK     | 12,000        | 350                | Periscope       | Attack #5 (Sunk)
    | 0902 | 139-48 E   |              |               | 8                  |                 |
7   | 7-30 | 43-15 N    | 2 PC-1       | 12,500        | 190                | SJ Radar        | Attack #6
8   | 2320 | 140-15 E   | Patrol Craft |               | 8                  |                 |

(G) AIRCRAFT CONTACTS:
    NONE.

                                  - 6 -
                                                ENCLOSURE (A)

— page 115 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET (SS408) TORPEDO ATTACK NO. 1. PATROL NO. 4.

TIME DATE LAT. LONG.
0115 (I) 28 JULY 1945 40 - 17 N. 139 - 50 E.

TARGET DATA

DESCRIPTION: One LARGE AK.

DETERMINED: Saw and heard three (3) torpedo hits. Target sunk to deck level
while under observation. As we chased the other three (3) ships
target suddenly disappeared from SJ radar PPI and A scope and
could not be seen. (Range 7,000 yards).

Ship's / Sunk: ONE (1).

Ship's / Damaged
or probable sunk: NONE.

TARGET DRAFT COURSE SPEED RANGE
24 ft. 180 10 2200

OWN SHIP DATA

SPEED COURSE DEPTH ANGLE (at firing)
10 100 Surface 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Night, Surface.

- 7 -
ENCLOSURE (A)

— page 116 —
U.S.S. SENNET (SS408)
C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA (Continued):

| | 5 | 1 | 2 | 3 | 4
|---|---|---|---|---|---|
| Tubes fired | . | 1 . | 2 | 3 | 4
| Track angle | 103 S | 103 S | 102 S | 107 S | 105 S
| Gyro angle | 002⁵⁰ R | 002⁴⁰ R | 004²⁰ R | 007¹⁰ R | 005²⁰ R
| Depth set | 10 | 6 | 6 | 6 | 6
| Power | High | High | High | High | High
| Hit or Miss | Hit | Hit | Hit | Miss | Miss
| Erratic | No | No | No | No | No
| Mark Torpedo | 14-3 A | 14-3 A | 14-3 A | 14-3 A | 14-3 A
| Serial | 26538 | 95282 | 64927 | 95109 | 64295
| Mark Exploder | 10-3 | 6-5 | 6-5 | 6-5 | 6-5
| Serial Number | 789 | 42627 | 27929 | 33610 | 26019
| Actuation Set | Contact & | Contact | Contact | Contact | Contact
| | Magnetic | | | |
| Actuation Actual | Contact | Contact | Contact | - | -
| Mark Warhead | 16-4 | 16-1 | 16-1 | 16-1 | 16-1
| Serial Number | 19995 | 15704 | 15701 | 20534 | 16070
| Explosive | Torpex | Torpex | Torpex | Torpex | Torpex
| Firing interval | 0 | 25 Sec. | 30 Sec. | 45 Sec. | 50 Sec.
| Spread | 0 | 100 R | 100 L | 200 R | 200 L
| Sea Condition | 1 | 1 | 1 | 1 | 1
| Overhaul Activity | U.S.S. SPERRY (AS12). (#26538, U.S. Submarine Base, Pearl
| | Harbor, T.H.).

- 8 -
ENCLOSURE (A)

— page 117 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA:

U.S.S. SENNET (SS408) TORPEDO ATTACK NO. 2. PATROL NO. 4.

TIME DATE LAT. LONG.
0405 (I) 28 JULY 1945 39 - 53 N. 139 - 43 E.

TARGET DATA

DESCRIPTION: One (1) large engines aft CARGO.

DETERMINED: Missed because target saw torpedoes and paralleled them.

Ship's / Sunk: NONE

Ship's / Damaged
or probable sunk: NONE

TARGET DRAFT COURSE SPEED RANGE
16 ft. 150 7.5 1800

OWN SHIP DATA.

SPEED COURSE DEPTH ANGLE (at firing)
3.3 040 60 ft. 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Night, Submerged, Periscope.

- 9 -

ENCLOSURE (A)

— page 118 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408).

(H) ATTACK DATA (Continued):

| | | | |
|---|---|---|---|
| Tubes fired | 5 | 1 | 2 |
| Track angle | 37 S | 38 S | 30 S |
| Gyro angle | 35°30' L | 34°30' L | 37°00' L |
| Depth set | 10' | 6' | 6' |
| Power | High | High | High |
| Hit or Miss | Miss | Miss | Miss |
| Erratic | No | No | No |
| Mark Torpedo. | 14-3 A | 14-3 A | 14-3 A |
| Serial | 64364 | 40253 | 64387 |
| Mark Exploder | 10-3 | 6-5 | 6-5 |
| Serial Number | 619 | 42728 | 33023 |
| Actuation Set | Contact & Magnetic | Contact | Contact |
| Actuation Actual | - | - | - |
| Mark Warhead | 16-1 | 16-1 | 16-1 |
| Serial Number | 29237 | 15696 | 20564 |
| Explosive | Torpex | Torpex | Torpex |
| Firing interval | 0 | 10 | 15 |
| Spread | Periscope 0 | Periscope 150' R | Periscope 150' L |
| Sea Condition | 2 | 2 | 2 |
| Overhaul Activity | U.S.S. SIMRAY (SS12) | | |

- 10 -
ENCLOSURE (A)

— page 119 —
U.S.S. SENNET (SS408).

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA:

U.S.S. SENNET (SS408) TORPEDO ATTACK NO. 3. PATROL NO. 4.

TIME DATE LAT. LONG.
0406 (I) 28 JULY 1945 39 - 53 N. 139 - 43 E.

TARGET DATA

DESCRIPTION: One (1) SMALL AK.

DETERMINED: Observed one (1) torpedo hit, and saw target sinking. On later
observation saw many survivors in water and no ship.

Ships / Sunk: ONE.
or probable sunk: NONE.

TARGET DRAFT COURSE SPEED RANGE
11 ft. 190 7.5 800

OWN SHIP DATA

SPEED COURSE DEPTH ANGLE (AT FIRING)
3.3 040 60 ft. 0

FILE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

- 11 -

ENCLOSURE (A)

— page 120 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)'

(H) ATTACK DATA (Continued):

Tubes fired                               6             3             1
Track angle                               123 S         135 S         128 S
Gyro angle                                90 R          103 R         95 R
Depth set                                 10'           6'            6'
Power                                     High          High          High
Hit or Miss                               Miss          Miss          Hit
Erratic                                   No            No            No
Mark Torpedo                              14-3 A        14-3 A        14-3 A
Serial                                    64794         26816         40792
Mark Exploder                             10-3          6-5           6-5
Serial Number                             555           33673         25164
Actuation set                             Contact &     Contact       Contact
                                          Magnetic
Actuation Actual                          -             -             Contact
Mark Warhead                              16-4          16-1          16
Serial Number                             26196         20540         19835
Explosive                                 Torpex        Torpex        Torpex
Firing interval                           0             10 S          20 S
Spread                                    Periscope     Periscope     Periscope
                                          0             150 R         150 L
Sea Condition                             2             2             2
Overhaul Activity                         U.S.S. SPERRY (.S12) (#64794, U.S. Submarine
                                          Base, Pearl Harbor, T.H.).

- 12 -

ENCLOSURE ( )

— page 121 —
C-O-N-F-I-D-E-N-T-I-A-L
U.S.S. SENNET (SS408)

U.S.S. SENNET (SS408)
TORPEDO ATTACK NO. 4.
PATROL NO. 4.

TIME
DATE
LAT.
LONG.

0408 (I)
28 JULY 1945
39 - 53 N.
139 - 43 E.

TARGET DATA

DESCRIPTION:
One (1) large engines aft CARGO.

DETERMINED:
Observed and heard two (2) torpedoes hit. Target was observed to
take a 15° down angle. About 15 minutes later C.O. observed two
(2) groups of survivors and life boats, one group being from
attack No. 3 and only one (1) target (attack No. 2) in sight.

Ship's / Sunk:
ONE (1).

Ship's / Damaged
or probable sunk:
NONE.

TARGET DRAFT
COURSE
SPEED
RANGE

16 ft.
150
7.5
1400

OWN SHIP DATA

SPEED
COURSE
DEPTH
ANGLE (at firing)

3.3
040
60 ft.
0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

- 13 -

ENCLOSURE (A)

— page 122 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(H) ATTACK DATA (Continued):

Tubes fired             7             8             10
Track angle             110 P         108 P         108 P
Gyro angle              179°          181°          182°
Depth set               4'            4'            4'
Power                   27.9          27.9          27.9
Hit or Miss             Hit           Hit           Miss
Erratic                 No            No            No
Mark Torpedo            18-1          18-1          18-1
Serial                  55628         100424        58217
Mark Exploder           8-7           8-7           8-7
Serial Number           16624         16957         16471
Actuation Set           Contact       Contact       Contact
Actuation Actual        Contact       Contact       -
Mark Warhead            18-2          18-2          18-2
Serial Number           6377          2906          6266
Explosive               Torpex        Torpex        Torpex
Firing interval         0             10 S          20 S
Spread                  Periscope     Periscope     Periscope
                        0             200 L         200 R
Sea Condition           2             2             2

Overhaul Activity       U.S. Submarine Base, Pearl Harbor, T.H.
Remarks                 Injection temperature 62°F. Battery temperature
                        used for speed correction 78°F.

- 14 -

ENCLOSURE (A)

— page 123 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA:

U.S.S. SENNET (SS408) TORPEDO ATTACK NO. 5. PATROL NO. 4.

TIME DATE LAT. LONG.
0935 (I) 30 JULY 1945 42 - 36 N. 139 - 48.5 E.

TARGET DATA

DESCRIPTION: One LARGE AK. (450 ft. in length estimated by radar range and
periscope divisions).

DETERMINED: Saw and heard two (2) torpedoes hit. Target immediately took a
large list to port and was observed to sink shortly thereafter.

Ship's / Sunk: ONE (1).

Ship's / Damaged
or probable sunk: NONE.

TARGET DRAFT COURSE SPEED RANGE
16 ft. 020 8 1650

OWN SHIP DATA

SPEED COURSE DEPTH ANGLE (at firing)
3.8 100 62 ft. 0

FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK: Day, Submerged, Periscope.

- 15 -

ENCLOSURE (A)

— page 124 —
C-O-N-F-I-D-E-N-T-I-A-L                               U.S.S. SENNET (SS/08)

(II) ATTACK DATA (Continued).

Tubes fired                               1             2             6
Track angle                             103 P         108 P         103 P
Gyro angle                              2° 50' L      7° L          3° L
Depth set                               6             6             10
Power                                   High          High          High
Hit or Miss                             Hit           Miss          Hit
Erratic                                 No            No            No
Mark Torpedo                            14-3 A        14-3 A        14-3 A
Serial                                  64721         92012         67060
Mark Exploder                           6-5           6-5           10-3
Serial Number                           33633         50200         661
Actuation Set                           Contact       Contact       Contact &
                                                                    Magnetic
Actuation Actual                        Contact       -             Contact
Mark Warhead                            16-1          16-1          16-1
Serial Number                           20247         5659          20011
Explosive                               Torpex        Torpex        Torpex
Firing interval                         0             10 S          17 S
Spread                                  Periscope     Periscope     Periscope
                                        0             250 L         250 R
Sea Condition                           1             1             1

Overhaul Activity                       U.S.S. SPERRY (AS12). (#67060, U.S. Submarine
                                        Base, Pearl Harbor, T.H.).

                                        - 16 -

                                                                    ENCLOSURE (A)

— page 125 —
C-O-N-F-I-D-E-N-T-I-A-L
                                                              U.S.S. SENNET (SS408)

(H) ATTACK DATA:

U.S.S. SENNET (SS408)                                        TORPEDO ATTACK NO. 6.         PATROL NO. 4.

TIME                                        DATE                                        LAT.                                        LONG.
0051 (I)                                    31 JULY 1945                                43 - 10 N.                                  140 - 18 E.

                                                                TARGET DATA

DESCRIPTION:             Similar to PC-1 Class

DETERMINED:               Believed all torpedoes ran under or missed the target.

Ship's / Sunk:            NONE

Ship's / Damaged
or probable sunk:       NONE.

TARGET DRAFT                                COURSE                                      SPEED                                       RANGE
8 ft.                                       162                                         7                                           2,600

                                                                OWN SHIP DATA

                                            COURSE                                      DEPTH                                       ANGLE (at firing)
SPEED
17.5                                        Fwd. 070 Aft. 270                           Surface                                     0

                                                                FIRE CONTROL AND TORPEDO DATA

TYPE ATTACK:             Night, Surface.

                                                                - 17 -

                                                                                                                            ENCLOSURE (A)

— page 126 —
O U.S.S. SENNET (SS408) : O

C-O-N-F-I-D-E-N-T-I-A-L
(H) ATTACK DATA (Continued):

Tubes fired                               3             4             7
Track angle                               101 S         100 S         115 S
Gyro angle                                14° R         12²⁰ R        7° R
Depth set                                 6'            6'            4'
Power                                     High          High          27.8
Hit or Miss                               Miss          Miss          Miss
Erratic                                   No            No            No
Mark Torpedo                              14-3 A        14-3 A        18-1
Serial                                    40254         40417         100456
Mark Exploder                             6-5           6-5           8-7
Serial Number                             33086         25425         15858
Actuation Set                             Contact       Contact       Contact
Actuation Actual                          -             -             -
Mark Warhead                              16-1          16-1          18-2
Serial Number                             15809         29527         5687
Explosive                                 Torpex        Torpex        Torpex
Firing interval                           0             12            1 Min. 15"
Spread                                    75 R          75 L          0
Sea Condition                             1"            1             1

Overhaul Activity                         U.S.S. SUBRY (AS12) (#100456, U.S. Submarine
                                          Base, Pearl Harbor, T.H.).

Remarks                                   Injection temperature, 62°F. Battery temperature
                                          used for speed correction 75°F.

                                          - 18 -

                                                                      ENCLOSURE (A)

— page 127 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(I) MINES:

NONE.

(J) ANTI-SUBMARINE MEASURES AND EVASION TACTICS:

Ship contacts #7 and #8 encountered off KOROI MISAKI were evidently
patrol boats brought out as a result of our activities of the previous few
days along the coast. They were steaming down the coast like a pair of
merchant ships. They had all the appearances of a trap.

(K) MAJOR DEFECTS AND DAMAGE:

NONE.

(L) RADIO:

Reception of the fox schedule was good during the entire patrol. At
night 9050 kc and 6045 kc gave the best results and during the day 13,665 kc
was the best frequency. The double keying on 9090 kc was difficult to copy.
Very little jamming was heard on the fox frequencies and that which was
encountered was very ineffective.

No ComSubPac serials were missed.

All messages were sent on primary ship-to-shore frequency. (4235 kc).

(M) RADAR:

SD-5 RADAR:

The SD-5 worked very satisfactorily throughout the patrol except for a
few days when the sensitivity was lost. New transmitter tubes were tried
but this did not help. Ground readings were taken on the antenna and these
readings were found to be very low, 150,000 ohms. When the bowl insulator
was washed and painted with a coat of glyptol, the resistance to ground
reading was well above fifty megohms and remained at this reading for the
remainder of the patrol. However, improving the ground reading did not
materially help the loss of sensitivity. Finally the trouble was discovered
in the RF section of the receiver where the contacts of the lighthouse tubes
were slightly corroded. When these tubes were cleaned off, the reception
came back to normal.

Reception on the SD-5 was a lot better than the SD-4 which was used
during the first three (3) patrols. Maximum ranges on planes up to fifty
(50) to fifty-five (55) miles were obtained.

- 19 -

ENCLOSURE (A)

— page 128 —
U.S.S. SENNET (SS408):

C-O-N-F-I-D-E-N-T-I-A-L
(M) RADAR (Continued):
SJ-1 RADAR:
    Performance of this radar was excellent during this patrol. It was used
    continuously going to and from the area. When we were near the Empire and in
    the area, the SJ was used as a surface search radar in order to avoid being
    detected, with the SJ being used very half hour to take a few sweeps.

    Failures in the SJ were a beat frequency oscillator, an 836 high voltage
    rectifier, a main power switch, and a 9001 neon lamp in the indicator. New 6
    AC 7 tubes were replaced in the IF strip to increase the gain.

ST RADAR:
    The ST's performance was excellent and no troubles were encountered.

APR-1:
    The APR-1 continued to give good results without any failures. It was
    used every night of the patrol and during the day when visibility was poor.

APR-5:
    This APR did not perform as well as was expected. For one thing the
    equipment was located too close to our other radar equipment and the constant
    interference from the ST or SJ rendered it almost useless. It is believed
    that a blanking out pulse from the SJ should be added. Secondly enroute to
    station it is believed the antenna flooded out, preventing the reception of
    any distant 10 centimeter radar.

IFF EQUIPMENT:
    Both the ABK and BN operated without material failures.

(N) SONAR GEAR AND SOUND CONDITIONS:
    Sound conditions on a whole were poor due to the large negative gradients
    encountered. As a result screws were not picked up outside a range of three
    (3) thousand yards.
    No trouble was encountered in the sound gear itself, but the training
    mechanism on the TDM on the QB head gave a lot of trouble. First, the micro
    switch was never built to stand the wear of constant use. Several switches
    failed before we realized it was necessary to rebuild the switch. The spring
    in the switch was replaced by a heavier spring and this lasted for several
    hundred hours. Second, the coupling between the motor and reduction gears
    chattered. The entire training mechanism needs realigning.

- 20 -
ENCLOSURE (C)

— page 130 —
U.S.S. SENNET (SS408)

C-O-N-F-I-D-E-N-T-I-A-L

(U) COMMUNICATIONS, RADAR, AND SONAR COUNTERMEASURES:
    SEE SPECIAL REPORT.

(V) REMARKS:
    NONE.

- 22 -

ENCLOSURE (A)

— page 131 —
SUBMARINE DIVISION ONE SIXTY-TWO

FB5-162/A16-3                                      Care of Fleet Post Office,
Serial: (019)                                      San Francisco, California,
                                                   9 August 1945.
C-O-N-F-I-D-E-N-T-I-A-L
FIRST ENDORSEMENT to
USS SENNET (SS 408)
Report of Fourth War
Patrol.

From:      The Commander Submarine Division ONE SIXTY-TWO.
To :       The Commander-in-Chief, United States Fleet.
Via :      (1) The Commander Submarine Squadron SIXTEEN.
           (2) The Commander Submarine Force, PACIFIC FLEET.
           (3) The Commander-in-Chief, U.S. PACIFIC FLEET.

Subject:   U.S.S. SENNET (SS 403) - Report of War Patrol
           Number FOUR.

           1. The fourth war patrol of the U.S.S. SENNET under
the command of Lieut. Commander C.R. CLARK, USN, was conducted in
the Japan Sea during the period 1 July 1945 to 9 August 1945.
After only three days in the area all torpedoes were expended
in six torpedo attacks.

           2. TORPEDO ATTACK NO. 1.
           An end around following an SJ contact at 14,000
yards resulted in an excellent firing position on a large AK. At
0111, 28 July five torpedoes were fired on the surface from
2,000 yards on a 103° starboard track resulted in three observed
hits. At 0118 target stopped shooting automatic weapons and SJ
contact was lost at 7,000 yards. It is considered this target
sank.

           ATTACKS NO. 2, 3 & 4.
           While gaining an attack position for attack #1,
three SJ contacts were obtained at 23,000 yards. Upon completion
of attack #1 these contacts were closed and a radar submerged
approach conducted in bright moonlight, 2,000 yards from the beach.
At 0340 targets were observed to be two large engine aft AK's and
one small AK. From an excellent position three salvoes were
fired within two minutes at three different targets indicating the
splendid fire control team-work of the SENNET. Three torpedoes
from the bow tubes fired at a large AK from 1,800 yards on a 37°
starboard track were avoided by the radical maneuvers of the
target. Three torpedoes from the bow tubes on 1,600 yards and
123° starboard track resulted in one hit in a small AK. Three
torpedoes from the stern tubes, range 1,400 yards, 110° port
track put two hits in a large AK.

                                     -1-

— page 132 —
SUBMARINE DIVISION ONE SIXTY-TWO
                                                    Care of Fleet Post Office;
                                                    San Francisco, California,
                                                    9 August 1945.

FB5-162/A16-3

Serial: (019)

C-O-N-F-I-D-E-N-T-I-A-L

FIRST ENDORSEMENT to
USS SENNET (SS 408)
Report of Fourth War
Patrol.

Subject:       U.S.S. SENNET (SS 408) - Report of War Patrol
               Number FOUR.

At 0409 SENNET was forced deep by the first target heading for
her periscope and two depth charges were dropped. Eleven minutes
later, at periscope depth, this target was observed heading away
and two groups of life boats with much debris were at the scene
of the attack. Results, one large and one small AK sunk.

                                                    ATTACK NO. 5.
               On 30 July in a daylight submerged attack, three
torpedoes fired from 1,650 yards on a 103° port track at a
large AK resulted in two observed hits at 0943. Target was
observed to capsize and sink at 0955. It is hoped that the
pictures obtained of this attack and sinking will aid in the
identification of this target.

                                                    ATTACK NO. 6.
               At 2320, 30 July SJ contact was made on two south
bound targets hugging the coast. Targets could not be made out
against the land background until the range had closed to 3,500
yards. They were identified as two PC boats. Two Mk. 14 tor-
pedoes set on six foot from forward, and one Mk. 18 torpedo set
on four feet from the after tube nest fired from about 2,600 yards
either under-ran the targets or missed due to the long range. The
targets were not alerted and SENNET retired on the surface.

3.             USS SENNET returned in very good material condition
and will be given a ten day re-fit by the U.S.S. ORION (AS 18).
The health and morale of the officers and men is excellent.

4.             The Administrative Division Commander is privileged
to congratulate the Commanding Officer, officers and men for this
outstanding, aggressive and productive patrol.

                                                    W. E. MERRALL.

— page 133 —
FC5-16/A16-3
Serial ( 037 )
C-O-N-F-I-D-E-N-T-I-A-L

SECOND ENDORSEMENT to
USS SENNET (SS 408)
Report of Fourth War Patrol.

From: The Commander Submarine Squadron SIXTEEN.
To : The Commander-in-Chief, United States Fleet.
Via : (1) The Commander Submarine Force, PACIFIC FLEET.
      (2) The Commander-in-Chief, U.S. PACIFIC FLEET.

Subject: U.S.S. SENNET (SS 408) - Report of War Patrol Number FOUR.

1. Forwarded concurring in the remarks of the Commander
Submarine Division One Sixty-Two.

2. In his first patrol as Commanding Officer, Lieut. Commander
C. R. CLARK, USN, led the SENNET in this skillful and daring penetration
of waters that are the enemy's most vital remaining lifeline. Once in the
assigned area of operations, 8 ships were contacted in a period of 72-½
hours. All were brought under attack and four valuable ships were sunk.
The 1st, 2nd, 3rd and 4th attacks, delivered within two minutes, resulted in
two ships sunk. The target which successfully evaded the track the torpedoes
were fired on (38°) and probably sighted the periscope in time to help his
evasive maneuvers.

3. The Commander Submarine Squadron Sixteen heartily congra-
tulates the officers and men of the SENNET on this smartly executed, ag-
gressive and highly successful patrol, and recommends that the damage
inflicted be assessed as follows:

SUNK
1 AK, large; (EU) - - - - - - 7,500 tons (Attack No.1)
1 AK, small; (EU) - - - - - - 2,000 tons ( " No.3)
1 AK, large; (EU) - - - - - - 7,500 tons ( " No.4)
1 AK, large; (EU) - - - - - - 7,500 tons ( " No.5)
Total SUNK 24,500

SUBMARINE SQUADRON SIXTEEN

Care of Fleet Post Office,
San Francisco, California,
10 August 1945.

[HANDWRITTEN: 10 Aug 45]
[SIGNATURE: W. A. LENT]
W. A. LENT.

— page 134 —
FF12-10(A)/A16-3(18) SUBMARINE FORCE, PACIFIC FLEET
Serial 02118 Care of Fleet Post Office,
San Francisco, California,
CONFIDENTIAL 23 August 1945.

THIRD ENDORSEMENT to NOTE: THIS REPORT WILL BE
SEANET Report of DESTROYED PRIOR TO
Fourth War Patrol ENTERING PATROL AREA.
[HANDWRITTEN: mr]
[HANDWRITTEN: 9 0173]

COMSUBSPAC PATROL REPORT NO. 856
U.S.S. SEANET - FOURTH WAR PATROL.

From: The Commander Submarine Force, Pacific Fleet.
To : The Commander in Chief, United States Fleet.
Via : The Commander in Chief, U.S. Pacific Fleet.

Subject: U.S.S. SEANET (SS408) - Report of Fourth War Patrol
(1 July to 9 August 1945).

1. The fourth war patrol of the SEANET, under the command of Lieutenant
Commander C. R. Clark, U.S. Navy, his first as commanding officer, was conducted in
the Japan Sea off the northwest coast of Honshu and the west coast of Hokkaido.

2. The SEANET spent only three days in her assigned area. During this
time she took advantage of every opportunity to strike the enemy and succeeded
with much dispatch in sinking four ships. The daring and skill displayed by the
SEANET in penetrating these dangerous home waters of the enemy, and the determina-
tion and aggressiveness with which attacks were conducted are deserving of the
highest praise.

3. Award of Submarine Combat Insignia for this patrol is authorized.

4. The Commander Submarine Force, Pacific Fleet, takes great pleasure
in congratulating the commanding officer, officers, and crew of the SEANET for
this aggressive, daring and outstanding patrol in very hazardous waters. Each
officer and man is deserving of the greatest praise for this patrol. The SEANET
is credited with having inflicted the following damage upon the enemy during this
patrol:

S U N K
1 - Large AK (EU) - 7,500 tons (Attack No. 1)
1 - Small AK (EU) - 2,000 tons (Attack No. 3)
1 - Large AK (EU) - 7,500 tons (Attack No. 4)
1 - Large AK (EU) - 7,500 tons (Attack No. 5)

TOTAL SUNK 24,500 tons

[SIGNATURE: G. C. CRAWFORD,]
Chief of Staff.

Authentication and distribution [STAMP: EXTRA] - ORIGINAL
on next page. [STAMP: SORG] - MICRO
[STAMP: PHOTO-LAB] - OP-16
[STAMP: RETURN TO F-4253]
[HANDWRITTEN: - 1 -]

— page 135 —
FF12-10(A)/A16-3(18)
Serial 02118
CONFIDENTIAL
THIRD ENDORSEMENT to
SENNET Report of
Fourth War Patrol.

SUBMARINE FORCE, PACIFIC FLEET

Care of Fleet Post Office,
San Francisco, California,
23 August 1945.

NOTE: THIS REPORT WILL BE
DESTROYED PRIOR TO
ENTERING PATROL AREA.

COMSUBSPAC PATROL REPORT NO. 856
U.S.S. SENNET - FOURTH WAR PATROL.

Subject: U.S.S. SENNET (SS408) - Report of Fourth War Patrol
(1 July to 9 August 1945).

DISTRIBUTION:
(Complete Reports)
Cominch (7)
CNO (5)
Cincpac (6)
JICPOA (1)
AdJICPOA (1)
Comservpac (1)
Cinclant (1)
Comsubslant (8)
S/M School, IL (2)
CO, S/M Base, PH (1)
Consopac (2)
Comsovespac (1)
Comsubs7thFlt (Fwd Echelon) (2)
Comsubs7thFlt (Rear Echelon) (2)
Comnorpac (1)
Comsubspac (3)
ComsubspacAdCond (40)
SUBAD, MI (2)
ComsubspacSubordCom (3)
All Squadron and Division
Commanders, Pacific (2)
ComSubOpTraGrBalboa (Airmail) (5)
Substrainpac (2)
All Submarines, Pacific (1)

[HANDWRITTEN: O.K.]
[SIGNATURE: E. L. Hynes]
E. L. HYNES, 2nd,
Flag Secretary.

— page 136 —
SS408/A16-3
Serial: 004-45.

[HANDWRITTEN: 4WP] [HANDWRITTEN: ①]
U.S.S. SENNET (SS408)

                                                                Care of Fleet Post Office,
                                                                San Francisco, California.

                                                                9 August 1945.

[STAMP: DECLASSIFIED]
[STAMP: CONFIDENTIAL - OPNAV INST 5510.20]
[HANDWRITTEN: BY J. Kien DATE 4 Oct '60]

From:           The Commanding Officer.
To:             The Commander-in-Chief, United States Fleet.
Via:            (1) The Commander Submarine Division
                (2) The Commander Submarine Squadron
                (3) The Commander Submarine Force, Pacific Fleet.
                (4) The Commander-in-Chief, U. S. Pacific Fleet.

Subject:        U.S.S. SENNET - Special Secret Transit Report on Entry and
                Exit to SEA of JAPAN, Patrol No. FOUR.

Enclosure:      (A) Subject Report

1.              Enclosure (A) is forwarded herewith.

                                                                C. R. CLARK.

[STAMP: DECLASSIFIED]

[HANDWRITTEN (vertical, right margin): Sent to FOC/P.F. BOX # A5-5006 RS # 1011 FILE A16(C) JACKET # 3326]

— page 137 —
S-E-C-R-E-T
SPECIAL TRANSIT REPORT

U.S.S. SENNET (SS408)

ENTRY VIA TSUSHIMA

(A) NAVIGATIONAL DATA:

(1) Entry into the JAPAN SEA

(a) Position - Start Submerged: Lat: 34 - 11.9 N. Long: 128 - 54.6 E.
(b) Time - Date 0300 (I) 25 JULY 1945
(c) Course 028°(T)
(d) Speed (RPM) 60
(e) Depth - Angle 140 feet 4½° up
(f) Position - on surfacing Lat: 35 - 10 N. Long: 129 - 42 E.
(This position is not too accurate)

(B) WEATHER:

(a) Weather Complete overcast, wind force 3 from
East, Sea choppy.
(b) CURRENT None observed.
(c) Sea Temperature 75°
(d) Gradient 15° drop from 100' to 130'.
(e) Sea Condition Force 3 at start. Force 1 at finish.

(C) MINE CONTACTS:

(a) Number of contacts (1) (2) (3)
15 6 1
(b) Locations 34-23 N 34-26.7 N 34-34.5 N
129-02.5 E 129-05 E 129-10.4 E
(c) Number of lines (a) 6 (a) 4
2 (b) 9 (b) 2
(d) Any indication as to depth - -
at which mines laid

- 1 -

ENCLOSURE (A)

— page 138 —
U.S.S. SENNET (SS408)

S-E-C-R-E-T
-------

SPECIAL TRANSIT REPORT (Continued):
U.S.S. SENNET (SS408)                                  ENTRY VIA TSUSHIMA

(e) Interval of lines (yds)           800             500

(f) Spacing of Mines (yds)            Line 1 60 Random
                                      Line 2 Random

(g) Direction of lines                305°            310°

(D) GLA PERFORMANCE:

    (a) False Contacts                35 False or possible contacts were experienc-
                                      ed as indicated on track chart.

    (b) Maximum ranges                800 yds on sure mine contacts.

        Minimum ranges                100' on possible contacts

    (c) Previous tests.
        (Triplane, F.T. Shells)       PTS 500 yards.

    (d) Casualties                    Pearl to Guam:
                                      The box containing the micro limit switches
                                      was misaligned which caused the screws at the
                                      threads at one end of the shaft to be sheered
                                      off and the side of the box to be distorted
                                      in shape. This resulted in the inoperation
                                      of all micro switches and consequently train-
                                      ing in the conning tower was impossible.

                                      Transit
                                      For a short time the FMO failed to recycle
                                      but this was quickly remedied by turning on
                                      a portable blower rigged to cool the
                                      thyratrons.
                                      The push button switch in the conning tower
                                      stuck and failed to operate.
                                      Lost narrow scan a little while after due
                                      to shaft in limit switch box becoming loose.
                                      The head was trained by hand during remainder
                                      of transit.

- 2 -
ENCLOSURE (A)

— page 139 —
U.S.S. SENNET (SS408)

S-E-C-R-E-T

SPECIAL TRANSIT REPORT (Continued):
U.S.S. SENNET (SS408) ENTRY VIA TSUSHIMA

— page 141 —
U.S.S. SENNET (SS408)

S-E-C-R-E-T

SPECIAL TRANSIT REPORT (Continued):
U.S.S. SENNET (SS408)                                        ENTRY VIA TSUSHIMA

(P) NARRATIVE (Continued):

     0833     In a beautiful position for a shot but only 140 miles from point
              B so let it go by with shooting a few pictures.
     1007     Surfaced.

27 July 1945.
     1200     Position: Lat. 40 - 27.8 N. Long. 138 - 11.8 E.
     2000     Arrived in area. SEE PATROL REPORT.

SHIP CONTACTS ENROUTE STATION:

No. | Lat.      | Long.       | Course | Speed | Type
----||||-------|
1   | 33 - 56 N | 128 - 50 E  | 180    | -     | PG
2   | 34 - 00 N | 128 - 34 E  | 200    | -     | DE & PG
3   | 35 - 40 N | 129 - 55 E  | 000    | -     | LARGE AK
4   | 36 - 20 N | 131 - 24 E  | 170    | 8     | SMALL AK
5   | 36 - 37 N | 131 - 40 E  | 310    | 7     | SMALL AK

                                  - 5 -

                                                          ENCLOSURE (A)

— page 142 —
S-E-C-R-E-T

SPECIAL TRANSIT REPORT

U.S.S. SENNET (SS408)                                 STRAITS:     LA PEROUSE

(A) NAVIGATIONAL DATA:

    (1) Exit from Sea of Japan.

        (a) Position - Start Surfaced     Lat. 45 - 51.2 N.     Long. 141 - 14.1 E.

        (b) Time - Date                   2032 (I)              31 July 1945

        (c) Course                        110°T.

        (d) Speed (RPM)                   20 knots

        (f) Position - end of transit     Lat. 45 - 28.4 N.     Long. 142 - 42.4 E.

        (g) Time - Date                   2340 (I)              31 July 1945

(B) WEATHER:

    (a) Weather                           1. Completely overcast and foggy.
                                          2. Force #1 sea.
                                          3. Force #1 wind.

    (b) Current                           2 knot current 110°T. after passing
                                          SOYA MISAKI.

    (c) Sea Temperature                   60°F.

    (d) Gradient                          Unknown.

    (e) Sea Condition                     Force 1.

(C) MINE CONTACTS:

    NONE

(D) OLA PERFORMANCE:

    -

                                          - 6 -

                                                                ENCLOSURE (A)

— page 144 —
S-E-C-R-E-T

U.S.S. SENNET (SS408)

SPECIAL TRANSIT REPORT (Continued):

U.S.S. SENNET (SS408)                               STRAITS: LA PEROUSE

(G) NARRATIVE:

31 July 1945.
    0330        Departed Station, headed for LA PEROUSE.
    1817        Sighted Russian Merchant Ship 050°T., range 14,000 yds., course
                000°T. Avoided him.
    1903        Sighted Russian Merchant Ship 125°T., range 15,000 yds., course
                180°T. Avoided him.
    2032        Commenced Transit of LA PEROUSE.
    2340        Completed Transit of LA PEROUSE.
    1200 Position: Lat. 45 - 42 N. Long. 139 - 19 E.

1 August 1945.
    1630        Made transit of ETOROFU STRAITS.
    1200 Position: Lat. 45 - 53 N. Long. 147 - 22 E.

2 August 1945.
    1200 Position: Lat. 44 - 15 N. Long. 153 - 50 E.

3 August 1945.
    1200 Position: Lat. 44 - 15.30 N. Long. 145 - 08 E.

4 August 1945.
    1200 Position: Lat. 36 - 11 N. Long. 142 - 16 E.
    1800        Received change of orders, now proceeding to SAIPAN for refit.

5 August 1945.
    1200 Position: Lat. 30 - 55 N. Long. 140 - 05 E.

6 August 1945.
    1200 Position: Lat. 25 - 15 N. Long. 139 - 55 E.

7 August 1945.
    1200 Position: Lat. 20 - 20 N. Long. 140 - 20 E.

8 August 1945.
    1200 Position: Lat. 16 - 30 N. Long. 144 - 20 E.

9 August 1945.
    1000        Arrived SAIPAN.

                                - 8 -

                                                    ENCLOSURE (A)

— page 145 —
SECRET

COMMANDER SUBMARINE FORCE
UNITED STATES PACIFIC FLEET
Hr
12 August 1945.

ADMIRAL'S COMMENTS ON U.S.S. SENNET - Transit Report.

By CO - Swift and decisive in best SENNET tradition--and displaying
plenty of guts.

Your resourcefulness when your gear went out of commission in
Tsushima Strait was of a high order.

I congratulate you and all hands on a most successful transit
and invasion of the enemy's private sea.

C. A. LOCKWOOD, Jr.

— page 146 —
END OF REEL
JOB NO. [HANDWRITTEN: H-108]

[Resolution Chart Numbers]
1.0 | 4.5 | 2.8 | 2.5
    | 5.0 | 3.2 | 2.2
    | 5.6 | 3.6 | 2.0
    | 6.3 | 4.0 | 1.8
1.1
1.25 | 1.4 | 1.6

THIS MICROFILM IS
THE PROPERTY OF
THE UNITED STATES
GOVERNMENT

[Seal: DEPARTMENT OF DEFENSE, UNITED STATES OF AMERICA]

MICROFILMED BY
NPPSO-NAVAL DISTRICT WASHINGTON
MICROFILM SECTION