On 22 February, Pompon departed on her fourth patrol, and operated in the vicinity of Halmahera Island. She launched four torpedoes at three small Japanese escort vessels, but they ran under their targets due to the escorts' shallow draft. A contact was made in Roeang Passage, but upon closing, it proved to be a hospital ship. She made no further contacts and proceeded to Pearl Harbor via Ascension and Midway, arriving 10 April. Fifth war patrol, May – June 1944 After a refit and four days training, Pompon was again ready for sea. She departed Pearl Harbor on 6 May 1944 for a patrol off the coasts of Kyūshū, Shikoku, and Honshū. On 30 May she contacted a 742-ton cargo ship off Muroto Zaki. A submerged attack resulted in a hit directly under the rising sun flag amidships, breaking the ship in two. The Shiga Maru immediately sank. For the next seven hours Pompon was the target for five Japanese escorts and a portion of the air force, but she managed to crawl away from the scene at deep submergence. After covering the Tokyo Bay approaches for the Battle for Saipan, Pompon returned to Midway 25 June. Sixth war patrol, July – September 1944 On 19 July Pompon departed on her sixth and most successful patrol. Operating from the eastern coast of Honshū to the Sea of Okhotsk, she sank a 300-ton armed trawler with gunfire. Then on 12 August she spotted a Japanese convoy off the coast of Russian Sakhalin. In the wild night surface action which followed an 8,000-ton tanker was badly damaged by two torpedoes, 2,718-ton transport Mikage Maru No. 20 was sunk, and a hit was possibly obtained on one of two hotly pursuing escort vessels. During this melee Pompon was almost sunk by one of her own torpedoes. While she was surfaced, with the enemy bearing down, one of her own "fish" perversely circled and just missed the stern. She was driven down by gunfire and then depth charged, but managed to escape without damage. She returned to Pearl Harbor 3 September for onward routing to San Francisco Bay for modernization and overhaul conducted at the Mare Island Navy Yard. Seventh war patrol, December 1944 – February 1945 By 13 December the veteran submarine was again at sea. En route to Majuro she picked up a Filipino who had been drifting in a broken down