patrol. Detecting a group of four escorted transports north of Palau on 21 July, she maneuvered into position and sank Saipan Maru (5532 tons). The depth charge attacks of the accompanying ships were ineffective. That same day Haddock came upon two unescorted tankers. Her first attack failed to sink the two ships, but she followed the ships and made two more attacks before finally breaking off the action for lack of torpedoes. Haddock arrived at Midway on 6 August and at Pearl Harbor four days later. Haddocks sixth war patrol was conducted in waters off Truk, the vital Japanese base in the Carolines. Departing Pearl Harbor on 2 September, she torpedoed the collier; Samsei Maru (641tons) on 15 September but failed to sink her, and the victim turned to ram the submarine. Haddock damaged the auxiliary tanker (14,050 tons) on 20 September forcing the tanker to return to Truk at reduced speed along with her 8000 tons of oil originally destined for Japan herself. The next day she torpedoed and damaged the Japanese collier Shinyubari Maru (5354 tons) and then spent a harrowing day eluding the attacks of Japanese escort vessels alerted by the explosions. She returned to Midway on 28 September with all torpedoes expended. The veteran submarine departed on her seventh war patrol on 20 October 1943 and headed again for the waters off Truk. Late on 1 November, Haddock attacked the Japanese cable-layer Tateishi and trawler Kitagami Maru without success, barely surviving the attacks of a hunter-killer group a few hours later. She made one additional attack on 6 November heavily damaging fleet tanker Hoyo Maru (8691 tons) with a torpedo into the stern temporarily forcing her abandonment, before returning to Pearl Harbor on 15 November 1943. Eighth and ninth war patrols, December 1943 – May 1944 For her eighth war patrol Haddock joined a coordinated attack group with and . She departed Pearl Harbor on 14 December and rendezvoused on 17 December. Encountering a group of warships on 19 January, Haddock attacked escort carrier (17830 tons) and damaged her severely with at least two hits before being driven off by the carrier's screening vessels. The submarine returned to Pearl Harbor on 5 February 1944. Haddock departed for her ninth war patrol 10 March. Under the USN's relentless attack, spearheaded by the submarines, Japan's sea lifelines had shrunk to a trickle and targets were scarce, but Haddock