Haddock was a Gato-class submarine, SS-231, named for a small Atlantic fish related to the cod. An earlier submarine had been laid down under the name and was renamed K-1 on 17 November 1911, before her launching, so this boat was the first to carry Haddock in service. uboat.net dates the order 28 June 1940. Portsmouth Navy Yard laid her down on 31 March 1941. Mrs. William H. Allen sponsored her at the launching on 20 October 1941, and Mrs. J. A. Rossell stood as maid of honor. One list prints the launch as 21 October. The Navy commissioned her on 14 March 1942. Arthur Howard Taylor had her.
She shook down off New England. On 17 May 1942 she arrived at Newport, Rhode Island, from Portsmouth for torpedo trials, and on 19 May she arrived at New London. She left New London for the Pacific on 19 June, passed through the Panama Canal on 3 July, and reached Pearl Harbor on 16 July. The first war patrol left Pearl on 28 July for the East China Sea. She was the first submarine to take the new SJ surface radar on a war patrol. On 22 August she sank the transport Tatsuho Maru, 6,334 gross tons, off the China coast near Foochow, at 26°07′ N, 121°29′ E. On 26 August she sank Teishun Maru, 2,251 gross tons, about 100 miles north-northwest of Keelung, at 26°27′ N, 121°23′ E. The patrol ended at Midway on 19 September.
The second patrol left Midway on 11 October for the East China Sea and the Yellow Sea. On 3 November she sank Tekkai Maru, 1,925 gross tons, at 32°02′ N, 126°13′ E. On 6 November she damaged France Maru, 2,732 gross tons, east of Cheju-do, at 33°46′ N, 127°28′ E. On 11 November she sank Venice Maru, 6,571 gross tons, in the Yellow Sea, at 35°36′ N, 123°44′ E. On 16 November she sank Nichinan Maru, 6,503 gross tons, at 31°52′ N, 126°14′ E. She was back at Pearl Harbor on 4 December. A Presidential Unit Citation later covered this patrol together with the fifth, sixth, and seventh.
Arthur Howard Taylor took her out of Pearl Harbor on 28 December 1942, to the waters south of Honshu. The Dictionary of American Naval Fighting Ships records an unidentified freighter of about 4,000 tons on 17 January 1943, and two hits on the last of six cargo ships on 19 January. uboat.net records the tanker Genyo Maru, 10,018 gross tons, that day at 34°13′ N, 136°59′ E. She ended the patrol at Midway on 17 February. On 5 March 1943 Taylor turned her over to Roy Milton Davenport.
Davenport had her until 1 December 1943. The fourth patrol left Midway on 11 March for the waters off Palau. On 3 April she sank the fleet tanker Arima Maru, 7,389 gross tons, north of Palau, at 10°26′ N, 135°00′ E. The next day, at 09°31′ N, 133°39′ E, depth charges damaged her and the patrol ended. She reached Pearl Harbor on 19 April. The fifth left Pearl on 30 June for the Carolines. On 21 July she sank the troop transport Saipan Maru, 5,532 gross tons. uboat.net prints the position 16°18′ N, 134°04′ E, and calls the place off Saipan. That position lies well west of the island. She was back at Pearl Harbor on 10 August.
The sixth patrol left Pearl Harbor on 2 September for the waters off Truk. On 15 September she damaged the collier Sansei Maru, 641 gross tons, at 09°32′ N, 150°38′ E. On 20 September she damaged the fleet tanker Notoro, 14,050 gross tons, at 07°23′ N, 150°11′ E. On 21 September she damaged the collier Shinyubari Maru, 5,354 gross tons, at 08°53′ N, 148°30′ E. The patrol ended at Midway on 28 September. The seventh left Midway on 20 October, again off Truk. She damaged the fleet tanker Hoyo Maru, 8,691 gross tons. The Dictionary dates that damage 2 November. uboat.net dates it 6 November, at 08°08′ N, 149°45′ E. She reached Pearl Harbor on 15 November.
John Paul Roach had her from 1 December 1943 to 7 February 1945. The eighth patrol left Pearl Harbor on 14 December with Tullibee and Halibut (SS-232), for the waters off Truk. On 19 January 1944, about 140 miles east-southeast of Guam, near 12°12′ N, 146°26′ E, she hit the escort carrier Unyo. Three torpedoes struck the starboard side, forward, and one was a dud. The bow sagged. Unyo stayed underway and was not sunk. In the first days of February a storm off Tateyama tore the damaged bow off, and she had to steam backward. Barb (SS-220) sank Unyo on 17 September 1944, southeast of Hong Kong. Haddock was back at Pearl Harbor on 5 February.
The ninth patrol left Pearl Harbor on 10 March 1944 for the Bonin Islands and ended there on 10 May. One account dates the auxiliary minesweeper Noshiro Maru No. 2 on 24 April 1944. Another prints 17 April. The tenth patrol left Pearl Harbor on 8 October with Halibut (SS-232) and Tuna, for the Philippines. On 25 October she was off Cape Engaño and went after Japanese ships that were retiring. The pursuit did not end in a hit. She reached Pearl Harbor on 10 December.
The eleventh patrol left Pearl Harbor on 23 January 1945 for the Ryukyus, with Roach still in command. William Herman Brockman, Jr. relieved him on 7 February and brought the patrol into Guam. uboat.net dates the arrival 14 March. A patrol-report line puts the return around 19 March, in company with Tigrone, Bullhead, and Seahorse, and the escort PC-824. Brockman turned her over on 27 March.
Albert Rowe Strow had her from 27 March 1945 until 23 April 1946. The twelfth and thirteenth patrols were uneventful. She ended the last war patrol at Pearl Harbor on 22 August 1945. On 19 April, northwest of Guam, she exchanged recognition with Icefish. The report gives 16°01′ N, 141°00′ E. On 30 July she exchanged recognition with Seahorse, northeast of Torishima. Every war patrol except the twelfth was marked successful. She received a Presidential Unit Citation for the second, fifth, sixth, and seventh, and the Asiatic-Pacific Campaign Medal with eleven battle stars.
She came back to the Atlantic. She was placed in reserve, still in commission, on 20 April. The Dictionary sets that day nearly four years after she had left the North Atlantic for the Pacific. On 12 February 1947 she was decommissioned at New London. Strow had already left her. In August 1948 she went into service as a Naval Reserve training boat in the Sixth Naval District. She was out of service in May 1952 at New London, in the Atlantic Reserve Fleet, and in service again in June 1956 at Portsmouth, New Hampshire. NavSource and Wikipedia strike her on 1 June 1960. The Dictionary and the Naval Cover Museum put the strike on 23 August 1960, the day she was sold for scrap to Jacob Checkoway. A later nuclear submarine, SSN-621, carried the name after the sale.