I-71, later I-171, was a cruiser submarine of the KD6 sub-class built for the Imperial Japanese Navy during the 1930s. She served in World War II, and took part in operations supporting the attack on Pearl Harbor, the Battle of Midway, and the Aleutian Islands campaign. She was sunk in February 1944. Construction and commissioning Built by Kawasaki at Kobe, Japan, I-71 was laid down on 15 February 1933 and launched on 25 August 1934. She was completed and commissioned on 24 December 1935. Service history Pre-World War II Upon commissioning, I-71 was assigned to the Kure Naval District. As the Imperial Japanese Navy began to deploy in preparation for the impending conflict in the Pacific, I-71 was assigned to Operation Z, the planned Japanese attack on Pearl Harbor, as a unit of Submarine Division 20 in Submarine Squadron 3, which in turn was assigned to the 6th Fleet′s Advanced Expeditionary Force. On 11 November 1941, I-71 departed Saeki, Japan, bound for Kwajalein in company with , , , , and . She arrived at Kwajalein on 20 November 1941. World War II First war patrol On 23 November 1941, I-69 departed Kwajalein to begin what would become her first war patrol. She received the message "Climb Mount Niitaka 1208" () from the Combined Fleet on 2 December 1941, indicating that war with the Allies would commence on 8 December 1941 Japan time (7 December 1941 in Hawaii). On 5 December 1941, I-71 conducted a reconnaissance of Alalakeiki Channel in the Hawaiian Islands between Maui and Kahoolawe. She and I-73 later reconnoitered Lahaina Roads between Maui and Lanai, finding no U.S. warships there. On 7 December 1941, the submarines of Submarine Squadron 3 operated south of Oahu to intercept any U.S. ships which attempted to sortie from Pearl Harbor during or after the Japanese attack there that day that brought Japan and the United States into World War II. I-71, I-72, and I-73 patrolled between southeast of Oahu. I-71 was subjected to several depth charge attacks during these operations. Departing Hawaiian waters, I-71 surfaced off Johnston Island on 21 December 1941 to attempt a bombardment of the island with her deck gun, but coastal artillery opened fire on her and forced her to submerge. She returned to Kwajalein on 28 December 1941. Second war patrol On 12 January 1942, I-69 departed Kwajalein along with I-72 and I-73 to begin her