I-46 was the first of three Type C cruiser submarines of the C2 sub-class built for the Imperial Japanese Navy. Commissioned in February 1944, she operated in World War II during the Battle of Leyte and Battle of Leyte Gulf before she was lost in October 1944. Design and description The Type C submarines were derived from the earlier KD6 sub-class of the with a heavier torpedo armament for long-range attacks. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of . For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the C1s had a range of at ; submerged, they had a range of at . The boats were armed with eight internal bow torpedo tubes and carried a total of 20 torpedoes. They were also armed with a single /40 deck gun and two single or twin mounts for Type 96 anti-aircraft guns. They were equipped to carry one Type A midget submarine aft of the conning tower. Construction and commissioning Ordered under the Rapid Naval Armaments Supplement Programme and built by the Sasebo Naval Arsenal at Sasebo, Japan, I-46 was laid down on 21 November 1942 with the name Submarine No. 376 and was numbered I-46 on 25 May 1943. Launched on 3 June 1943 and provisionally attached to the Yokosuka Naval District, she was completed and commissioned on 29 February 1944. Service history Upon commissioning, I-46 formally was attached to the Yokosuka Naval District and assigned to Submarine Squadron 11 for shakedown and work-ups. During a training sortie in the Iyo-nada on 2 April 1944, she collided underwater with the submarine off Minase Bight southwest of Kominasa Light at 21:45, suffering damage to her conning tower and periscopes. After repairs and testing, she arrived at Sasebo Navy Yard on 7 May 1944 for additional repairs. I-46 was reassigned to Submarine Division 15 in the 6th Fleet on 30 May 1944. On 12 August 1944, her commanding officer submitted a memorandum to the headquarters of the 6th Fleet and the commander of Submarine Squadron 11 suggesting improvements to the Type 13 air search radar installation and application of the anti-radar coating aboard I-46. On 13