The I-68 (later I-168) was a Japanese submarine whose keel was laid in 1931, launched in June 1933, and commissioned in the Imperial Japanese Navy in 1934. The length of the ship at the time of launching was 98 m, width 8.2 m, and the underwater displacement - 2,440 tons. The maximum surface speed of the I-68 reached 23 knots on the surface. The main armament was six 533 mm torpedo launchers, and the secondary armament was a single 120 mm gun and one 13.2 mm anti-aircraft machine gun.
The I-68 was a submarine of the Kaidai type (subtype: KD6A), developed on the basis of the experience gained during the operation of ships of the KD5 subtype. Compared to them, it had a slightly higher underwater displacement and slightly changed additional armament. However, it had a clearly higher surface speed. At the outbreak of World War II in the Pacific, he was operating in the Hawaii area, taking part in the Japanese attack on the base at Pearl Harbor on December 7, 1941. While carrying out the tasks he was assigned, he was damaged, which led to his directed to Kwajalein for minor repairs. In May 1942, the ship changed her designation from I-68 to I-168. The ship, already as the I-168, took part in the Battle of Midway in June 1942 with great success, when it sank the American destroyer USS Hammann and finished off the USS Yorktown aircraft carrier. After the Battle of Midway, the ship was sent for repairs to Japan, and in the second half of 1942 and in early 1943, she served in the Solomon Islands, and later in the Aleutian Islands. Ship I-168 was sunk on July 27, 1943 in the Rabaul area by the USS Scamp.
The I-370 was a Japanese submarine whose keel was laid in December 1943, launched in May 1944, and commissioned in the Imperial Japanese Navy in September 1944. The length of the ship at the time of launching was 73.5 m, width 8.9 m, and underwater displacement - 2,200 tons. The maximum surface speed of the I-370 was up to 13 knots on the surface. The main armament was two 533 mm torpedo launchers, and the secondary armament was a single 140 mm gun and two 25 mm Type 96 anti-aircraft guns.
The I-370 was a Type D submarine, which in turn was developed after the Battle of Midway and in connection with the changes in the Pacific War that this battle entailed. The D-class ships were supply and transport submarines based on the German U-155. They were to operate in waters where the enemy had a clear air advantage and to provide people, supplies and weapons to the Japanese garrisons in the Pacific. Originally, torpedoes of this type were not intended to be armed with torpedoes, but later the assumption was changed. Shortly after entering service, the I-370 was quickly modernized and converted into the carrier of Kaiten-class live torpedoes. The ship in this configuration could carry up to five such torpedoes, and was equipped with a Type 22 radar, but a 140 mm gun was removed from its deck. In January 1945, the crew underwent training in attacking with a new weapon, and in the second half of February of the same year, the I-370 was directed against the American troops landing on Iwo-Jima. However, the ship was sunk on February 26, 1945 south of Iwo-Jima in an attack with depth charges by destroyer USS Finnegan.