I-55, later renumbered I-155 (伊号第五五潜水艦, I-gō Dai-Hyaku-gojūgosensuikan), was an Imperial Japanese Navy Kaidai-class cruiser submarine of the KD3A sub-class commissioned in 1927.

Japanese strategists came to realize possibilities for using submarines for long-range reconnaissance and in a war of attrition against an enemy fleet approaching Japan.

The United States Navy′s Office of Naval Intelligence estimated that some 800 German advisors had gone to Japan by the end of 1920.

The Japanese also sent delegations to Germany, and were active in purchasing many patents related to submarine design and construction.

For surface running, the submarines were powered by two 3,400-brake-horsepower (2,535 kW) diesel engines, each driving one propeller shaft.

[6] Built by the Kure Naval Arsenal, I-55 was laid down on 1 April 1924 as Submarine No.78 (第七十八号潜水艦, Dai-nanajuhachi-gō sensuikan).

[7] During a training exercise on 11 July 1929 in which she simulated a submerged torpedo attack against the heavy cruiser Kinugasa, she accidentally collided with Kinugasa off Kyushu 20 nautical miles (37 km; 23 mi) southwest of Ōdate Shima lighthouse, sustaining substantial damage to her bow plating.

[7] At 13:48 on 10 February 1932, I-55′s sister ship I-54 suffered a steering failure off Kyushu 20 nautical miles (37 km; 23 mi) south of Odate Shima lighthouse while Submarine Division 18 was on maneuvers during fleet exercises.

[7] While the division was on maneuvers during fleet exercises off Kyushu on 10 May 1936, I-55 collided with her sister ship I-53,[7][11] sustaining minor damage to her bow plating.

[8] After her superstructure was partially dismantled, she was refloated and towed to Kure, Japan, on 31 July 1936, where she was drydocked for repairs.

[8] Imperial Japanese Navy torpedo planes sank the two capital ships in the South China Sea off the Malayan Peninsula on 10 December 1941 before the submarines could engage them.

[8] After the Japanese submarine Ro-34 expended all of her torpedoes in an attack on an Allied convoy, I-53, I-54, and I-55 received orders on 5 February 1942 to patrol in Ro-34ʼs area.

[8] The United States Navy patrol vessel USS Isabel (PY-10) arrived on the scene, rescued 187 people from Van Cloon, and opened fire on I-55 when I-55 attempted to surface nearby.

[8] Derrymore, which was on a voyage from Singapore to Batavia, Java, with a 7,000-ton cargo of military stores including ammunition and six crated Hawker Hurricane Mark II fighters and carrying 209 Royal Australian Air Force (RAAF) personnel, sank 90 minutes later about 5 nautical miles (9.3 km; 5.8 mi) north of Jason Rock and 12 nautical miles (22 km; 14 mi) southwest of Noordwachter Island in the Thousand Islands at 05°18′S 106°20′E / 5.300°S 106.333°E / -5.300; 106.333 (SS Derrymoore) with the loss of nine RAAF personnel.

[8] The Royal Australian Navy corvette HMAS Ballarat quickly rescued Derrymore′s entire crew of 36 (including four gunners) and the other 200 RAAF personnel aboard.

[8] On 18 February 1942, I-55 reported sinking an Allied merchant ship with gunfire, although her likely target, the 5,804-gross register ton Norwegian tanker SS Madrono, actually suffered no damage.

[8] Ordered to participate in the evacuation, I-155 departed Kure on 22 May 1943,[8] called at Yokosuka, Japan, on 23 May,[8] and then proceeded to Paramushiro in the northern Kuril Islands, being attached temporarily to the Kiska Evacuation Force as a unit of Submarine Squadron 1 in the Northern District Force of the 5th Fleet on 29 May 1943 along with the submarines I-2, I-7, I-21, I-24, I-34, I-36, I-156, I-157, I-168, I-169, and I-171.

[8] After returning to Kure from her abortive Aleutians service and completing repairs, I-155 resumed duties as a training ship.

[8] From 23 to 25 February 1944, however, she tested another camouflage scheme for the Naval Submarine School, painted bluish-gray and black.

[8] While submerged at 11:50 on 5 May 1944, she suffered damage in a collision with the hybrid oiler-seaplane carrier Hayasui off Kabuto-jima in Hiroshima Bay at longitude 140 degrees East,[8][25] and garbled Japanese message intercepted, decrypted, and translated by Allied signals intelligence indicated that her damage included a hole measuring 2 by 1 meter (6 ft 7 in by 3 ft 3 in).