The I-15 was a Japanese submarine whose keel was laid in 1938, launched in March 1939, and commissioned in the Imperial Japanese Navy in September 1940. The length of the ship at the time of launching was 108.7 m, width 9.3 m, and the underwater displacement - 3,600 tons. The maximum surface speed of the I-15 reached 23.5 knots on the surface. The main armament was six 533 mm torpedo launchers, and the secondary armament was a single 140 mm gun and two 25 mm Type 96 anti-aircraft guns. The ship also took one Yokosuka E14Y seaplane on board.
The I-15 was an ocean submarine of the B1 type, which in many design solutions was based on the Kaiden type, especially the KD6 type. However, it differed from its ancestors in size, especially in the underwater and surface displacement, as well as in the immersion depth, which increased to about 100 meters. Type B1 ships were also equipped with seaplanes, which gave them greater possibilities in terms of sea reconnaissance, they were also characterized by a large range and high surface speed. The I-15 - the first of the B1 type - at the outbreak of World War II in the Pacific, took part in the attack on the American naval base at Pearl Harbor, operating near the island of Oahu. Later, in the period May-June 1942, he operated in the area of the Aleutian Islands. Finally, from October 1942, he operated in the area of the Solomon Islands, where he supported Japanese troops fighting in Guadalcanal. The ship was sunk in the course of these operations on November 10, 1942 by the USS Southard.
The I-46 was a Japanese submarine whose keel was laid in 1942, launched in June 1943, and commissioned in the Imperial Japanese Navy in February 1944. The length of the ship at the time of launching was 108.7 m, width 9.3 m, and the underwater displacement - about 3,600 tons. The maximum surface speed of the I-46 was 23.5 knots on the surface. The main armament was eight 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-46 was an ocean submarine of type C (sub-type C2), which in turn was a development of the ships of sub-type C1. In essence, with almost identical sizes, both differed slightly in displacement, as well as the lack of special mounts on the C2 sub-type for attaching miniature submarines. Undoubtedly, they were ships of considerable size, with a considerable range, strong torpedo armament, capable of submerging up to a depth of 100 meters. The I-46 began her very brief participation in the war in the Pacific by being assigned to the 15th Submarine Squadron. In October 1944, the ship is directed to the Philippines, where it participates in actions against the American invasion fleet. It was most likely lost as a result of an accident or action by the American fleet on October 26 or 27, 1944.