aboard to begin her fourth war patrol in company with I-8, which was beginning the next leg of her Yanagi-mission voyage to France. I-10 refueled I-8 at on 1 July and again at on 6 July 1943 before the two submarines separated, I-8 proceeding on her voyage to France and I-10 beginning anti-shipping operations in the Indian Ocean. In the Gulf of Aden, I-10 hit the 7,634-gross register ton Norwegian tanker Alcides with two torpedoes on 22 July 1943. Alcides, which was on a voyage from Abadan, Iran, to Fremantle, Australia, sank at . I-10 took Alcides′s master, radio officer, and second mate aboard, and they remained prisoners of war in Japan until freed by American forces on 29 August 1945. I-10 returned to Penang on . Fifth war patrol With a five-man film crew embarked to capture footage for the propaganda film Gochin! ("Sunk!") and a Yokosuka E14Y1 (Allied reporting name "Glen") floatplane aboard, I-10 departed Penang at 16:00 on 2 September 1943 and headed back into the Indian Ocean to begin her fifth war patrol, assigned a patrol area in the Gulf of Aden. On 14 September, she torpedoed and sank the 6,361-gross register ton Norwegian tanker Bramora — which was carrying oil from Bandar Abbas, Iran, to Melbourne, Australia — southwest of the Chagos Archipelago at . At dawn on 20 September 1943, her floatplane flew a reconnaissance mission over Perim Island in the Bab-el-Mandeb to investigate a report that the Allies had constructed an airfield there, but its crew found no airfield on the island. I-10 returned to the Gulf of Aden, where at about 02:00 on 24 September 1943 she sighted the American 7,634-gross register ton Liberty ship southeast of Aden. She fired two torpedoes at 03:12, one of which struck Elias Howe, killing two men in her engine room and starting a large fire. Elias Howe transmitted an SOS. I-10 surfaced and hit Elias Howe with another torpedo, and 15 minutes after the second hit explosives aboard Elias Howe detonated. Elias Howe sank by the stern at . The Royal Navy armed trawler and a seaplane rescued Elias Howe′s survivors. At about 16:30 on 1 October 1943, I-10 sighted an Allied convoy in the Gulf of Aden heading west at and set out in pursuit. She fired three torpedoes at the 4,836-gross register ton Norwegian armed merchant ship , which was carrying a cargo