Patrol 1

15 Feb 1942 - 10 Apr 1942

石狩丸 Ishikari Maru

Patrol 2

4 May 1942 - 22 Jun 1942

No ships sunk (No attacks)

Patrol 3

15 Jul 1942 - 3 Sep 1942

Patrol 4

6 Oct 1942 - 16 Nov 1942

No ships sunk

Patrol 5

7 Dec 1942 - 31 Jan 1943

4 landing craft (1 identified as Y 38) of 8 tons each; small vessels not credited to Grayback in JANAC

Note that JANAC credits Grayback with sinking the submarine 伊18 I-18 (2,189 tons) . However, I-18 survived the attack. She was sunk on 11 February 1943 by USS Fletcher (DD-445).

Patrol 6

16 Feb 1943 - 4 Apr 1943

No ships sunk

Patrol 7

25 Apr 1943 - 30 May 1943

淀川丸 Yodogawa Maru

英蘭丸 England Maru

Patrol 8

26 Sep 1943 - 10 Nov 1944

高瑞丸 Kozui Maru

粟田丸 Awata Maru

富士丸 Fuji Maru - JANAC gives USS Shad (SS-235) shared credit for this shinking along with Grayback, although Alden credits Grayback only. Shad's only attack this day took place 6 hours before Fuji Maru was first hit.

Patrol 9

2 Dec 1943 - 4 Jan 1944

玉嶺丸 Gyokurei Maru

沼風 Numakaze

湖南丸 Konan Maru

柏丸 Kashiwa Maru

Genei Maru No. 5 - small fishing vessel (119 tons) not credited to Grayback in JANAC.

Patrol 10

28 Jan 1944 - 26 Feb 1944 (lost)

大敬丸 Taikei Maru (Daikei Maru in some sources)

東神丸 Toshin Maru

南邦丸 Nanpo Maru

Note that JANAC, Alden, and other sources credit Grayback with sinking 錫蘭丸 Ceylon Maru at 31-35N, 127-47E (west of Kyushu) on 27 February 1944. However, Grayback was probably sunk on 26 Feb 1944; and the location of Grayback's wreck, found east of Okinawa in 2019, is approximately 350 nautical miles from the location of Ceylon Maru's sinking.

USS Grayback was lost on this patrol.

Current research credits Grayback with sinking 13 ships, totaling 65,978 tons, plus 5 additional small vessels totalling 151 tons (4 landing craft of 8 tons each, and 1 small fishing vessel of 119 tons). This figures do not include the submarine I-18 and the cargo ship Ceylon Maru, neither of which were sunk by Grayback, but they do include full credit for sinking Fuji Maru.

JANAC credits Grayback with 14 ships sunk totalling 63,835 tons, including I-18 (2,180 tons) and Ceylon Maru (4,905 tons), and sharing credit with USS Shad (SS-235) for sinking Fuji Maru. Note that the criteria JANAC used included all Japanese Naval vessels (although JANAC did not usually count warships less than 500 tons that were converted from merchant ships) and all Japanese merchant vessels of 500 or more gross tons known or believed to have been lost during the war. Other differences between JANAC figures and current research are noted above.

Alden-McDonald credit Grayback with 19 ships and 71,034 tons sunk, including 4 landing craft (3 unnamed) of 8 tons each, 1 small fishing vessel of 119 tons. Alden includes Ceylon Maru, 4,905 tons, which evidence now shows not to have been sunk by Grayback. Alden does not credit Grayback with sinking I-18. Alden credits Grayback (only) with sinking Fuji Maru.

SORG credits Grayback with 24 ships and 94,700 tons sunk, including 4 landing craft with no tonnage listed.

Japanese Naval and Merchant Ship Losses - JANAC on the NHHC website

JANAC on the Hyperwar website - https://www.ibiblio.org/hyperwar/Japan/IJN/JANAC-Losses/JANAC-Losses-6.html

SORG- http://archive.hnsa.org/doc/subreports-sorg.htm (Excel spreadsheet download)

SORG on combinedfleet.com

Archives of the Pacific Fleet Submarine Museum (PFSM)

War Patrol Reports - USS Grayback

Monthly Losses of Combatant and Non-Combatant Vessels

太平洋戦争時の喪失船舶明細表（汽船主体）- Lost Vessel table during the Pacific War (merchant vessels)

Alden, John D., and McDonald, Craig R. - U.S. & Allied Sub Successes in the Pacific & Far East during WWII - Fourth Edition, 2009

Cressman, Robert - The Official Chronology of the U.S. Navy in World War II, Naval Institute Press, 2000.

NHHC - “Take Her Down!”— Commander Howard Gilmore and USS Growler (SS-215)

Wrecksite - https://www.wrecksite.eu/wrecksite.aspx

Miramar Ship Index - https://www.miramarshipindex.nz/

Imperial Japanese Navy Page - http://www.combinedfleet.com/

Wikipedia Japan - https://ja.wikipedia.org/wiki/グレイバック_(SS-208)

Japan Center for Asian Historical Records - National Archives of Japan - https://www.jacar.go.jp/index.html

Official U.S. Navy Photos - Naval History & Heritage Command

Archives of the Pacific Fleet Submarine Museum (PFSM)

Imperial Japanese Navy Page - http://www.combinedfleet.com/

Japanese Merchant Ship photos - Wrecksite - copyright owners retain all rights. Photos used on this site will be taken down should the owner request their removal.

Note on the painting above: The original painting was done by McClelland Barclay in 1943. This similar version is from submarinesailor.com, artist unidentified.