Haddock (SS-231) was laid down at the Portsmouth Navy Yard on 31 March 1941. She was launched on 20 October 1941 (sponsored by Mrs. William H. Allen), and commissioned on 14 March 1942, Lieutenant Commander Arthur H. Taylor (Class of 1927) in command.
After shakedown and training cruises off New England, Haddock sailed for the Pacific on 19 June 1942 and arrived Pearl Harbor 16 July. She departed on her first war patrol on 28 July, the first submarine to do so with the new SJ radar. This equipment added greatly to her power in seeking out and destroying enemy ships in darkness or reduced visibility.
Penetrating into the Bonin Islands–East China Sea area, Haddock attacked a freighter on the surface on 22 August, sinking troop transport Tatsuho Maru (6334 tons). Tatsuho Maru had suffered engine trouble and had fallen back; being left behind by her convoy making her easy prey for the new boat and crew. Haddock put a torpedo into her port side #4 hold where 10,000 gallons of aviation gasoline was stored. This caught fire and exploded. The ensuing damage took Tatsuho Maru down by the stern in five minutes, taking 26 passengers and 12 crewmen with her. In the Formosa Straits on 26 August Haddock fired four stern shots at Teinshum Maru (formally vichy french TAI SEUN HONG) but missed; the submarine swung around to bring her bow tubes to bear and sent the 2251 ton cargo ship to the bottom. Haddock patrolled off Okinawa before returning to Midway 19 September 1942.
Haddock's second war patrol, commencing 11 October from Midway, was carried out in the Yellow Sea. After two attacks without hits, the submarine torpedoed Tekkai Maru (1925 tons) amidships on 3 November, breaking her in two. She was forced to break off another attack on 6 November after damaging the IJA converted troop transport French Maru (5828 tons) because of destroyers and search aircraft, but during the night of 11–12 November blew off the stern of cargo ship Venice Maru (6571 tons) east of the island of Honshū. Haddock damaged another ship on Friday 13 November, only to be prevented from finishing her off by escort craft, and she expended her last torpedo on Nichinan Maru (6503 tons) on 16 November. After a brief gunfire duel with her victim, (the merchantman sunk later that day.) the submarine headed for Pearl Harbor, arriving on 4 December.
Haddock departed Pearl Harbor on 28 December on her third war patrol, this time to the oceans south of Japan. She was attacked by two destroyers raining depth charges, and when she finally surfaced to clear the area, Haddock found herself surrounded by Japanese patrol craft. The submarine sped out of the trap just in time to avoid destruction.