Ka-Tsu vehicles, the operation called for the vehicles to proceed to shore, move overland across the atoll′s islands, then enter the water in the lagoon and attack Allied ships with torpedoes. The operation was cancelled before any of the submarines could take part in it. First war patrol On 17 May 1944, I-53 departed Saeki, Japan, to begin her first war patrol, assigned a patrol area northeast of Kavieng on New Britain in the Bismarck Archipelago. While she was on the way to her patrol area, she was reassigned to Submarine Division 15 in the 6th Fleet on 19 May 1944. After that, her patrol passed uneventfully until 28 June 1944, when her crew discovered a serious diesel fuel leak in one of her fuel tanks. She departed her patrol area and called at Truk from 2 to 15 July 1944 to undergo temporary repairs, then embarked the commander of Submarine Squadron 7 and proceeded to Kure, which she reached on 25 July 1944. July–October 1944 I-53 arrived at Sasebo on 28 July 1944 and entered drydock there for repairs and an overhaul, during which shipyard workers renewed her anti-radar coating. In late August 1944, she was selected for conversion to carry kaiten manned suicide attack torpedoes. As part of the conversion, the deck gun abaft her conning tower was removed to make way for fittings for four kaitens on her after deck. On 13 October 1944, the Combined Fleet ordered the activation of Operation Shō-Gō 1, the defense of the Philippine Islands, in anticipation of an American invasion of the islands, Although her kaiten conversion was incomplete, I-53 was ordered to participate in Shō-Gō 1 as a conventional submarine, and on 13 October she received orders to join the submarines , , , and in forming Group "A" under the direct command of the 6th Fleet. Second war patrol I-53 departed Kure to begin her second war patrol on 19 October 1944, assigned a patrol area off the Philippines. On 20 October 1944, U.S. amphibious landings on Leyte began the Battle of Leyte. I-53 received orders on 21 October to proceed to waters in the Philippine Sea east of Leyte. Although the reaction of Japanese naval forces to the American invasion led to the Battle of Leyte Gulf, fought from 23 to 26 October 1944, I-53 saw no action during the battle, and her patrol was uneventful until 4