I-68, later renumbered I-168, was an Imperial Japanese Navy Kaidai–type cruiser submarine of the KD6 sub-class commissioned in 1934. She served in World War II, operating in support of the Japanese attack on Pearl Harbor and taking part in the Battle of Midway, the Guadalcanal campaign, and the Aleutian Islands campaign before she was sunk in 1943. She is best known for her achievements during the Battle of Midway when, under the command of Lieutenant Commander Yahachi Tanabe, she sank the only United States Navy warships lost in the battle: the already badly damaged aircraft carrier and the destroyer . Construction and commissioning Built by the Kure Naval Arsenal at Kure, Japan, I-68 was laid down on 18 June 1931 and launched on 26 June 1933. She was completed and commissioned on 31 July 1934. Service history 1934–1941 Upon commissioning, I-68 was attached to the Kure Naval District. When Submarine Division 12, previously deactivated in 1929, was reactivated on 8 October 1934 and subordinated to the Kure Naval District, I-68 and her sister ship I-69 were assigned to the division. Submarine Division 12 was assigned to Submarine Squadron 2 in the 2nd Fleet, a component of the Combined Fleet, on 15 November 1935. On 13 April 1936, I-68 got underway from Fukuoka, Japan, in company with the other two submarines of her division — I-69 and — for a training cruise off China in the Tsingtao area, which the submarines completed with their arrival at Sasebo, Japan, on 22 April 1936. The three submarines departed Mako in the Pescadores Islands on 4 August 1936 for a training cruise in the Amoy area off China, returning to Mako on 6 September 1936. Submarine Division 12 was placed in the Third Reserve in the Kure Naval District on 15 December 1938, then was attached directly to the Kure Naval District on 1 May 1939. Submarine Division 12 was reassigned to Submarine Squadron 3 in the 2nd Fleet on 15 November 1939. I-68 departed Okinawa on 27 March 1940 in company with I-69, I-70, and the submarines , I-74, and I-75 for a training cruise in southern Chinese waters, completing it when the six submarines arrived at Takao, Formosa, on 2 April 1940. On 11 October 1940, I-68 was one of 98 Imperial Japanese Navy ships that gathered along with more than 500 aircraft on the Japanese coast at Yokohama Bay for an