(Imperial War Museum photo, scanned from "Submarines of the Imperial Japanese Navy" by Polmar and Carpenter)

While similar to the KD4 type, these boats had an improved operating depth, and introduced the 10cm/65 cal. dual-purpose gun.  I--165 and I-166 were originally I-65 and I-66, respectively, until renumbered in 1942.  I-67 was lost, with 87 men, during an exercise in 1940, and thus was not renumbered.  I-165 had her gun removed in 1945 so that she could carry two Kaiten.  She was sunk east of Saipan on 27 June 1945.  I-166 was sunk by Brtish submarine HMS Telemachus off Singapore on 17 July 1944.