I-18 was one of five Type C cruiser submarines of the C1 sub-class built for the Imperial Japanese Navy. During World War II, she operated as the mother ship for a midget submarine during the attack on Pearl Harbor and the attack of Diego-Suarez, conducted a war patrol in the Indian Ocean, and served in the Guadalcanal campaign before she was sunk in February 1943. 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 3rd Naval Armaments Supplement Programme and built by the Sasebo Naval Arsenal at Sasebo, Japan, I-18 was laid down on 25 August 1937 with the name Submarine No. 38. Launched on 19 July 1939, she was completed and commissioned on 31 January 1941, by which time she had been renamed I-18. Service history Pre-World War II Upon commissioning, I-18 was attached to the Yokosuka Naval District, assigned to Submarine Division 2 in Submarine Squadron 1 in the 6th Fleet In the autumn of 1941, she underwent conversion into a mother ship for a Type A midget submarine. The submarines , , , and also underwent the conversion. By 15 November 1941, I-18 was a part of Submarine Division 3 — which also included and I-20 — in Submarine Squadron 1 in the 6th Fleet. At the Kure Navy Club in Kure, Japan, on 17 November 1941, the commander of Submarine Division 3 briefed the commanding officers of the five converted submarines on the upcoming attack on Pearl Harbor and on the role of their