I-168

The I-168: A Japanese Submarine That Made History in World War II

The I-168 served as a Kaidai-class submarine of the KD6A sub-class built for the Imperial Japanese Navy under its original designation I-68. Commissioned in 1934 the I-168 emerged as a powerful submarine built to function as a long-distance cruiser vessel which supported Japanese naval campaigns during World War II. The I-168 became famous for its pivotal participation in numerous decisive battles including the Battle of Midway where it destroyed two U.S. Navy vessels such as the aircraft carrier USS *Yorktown*. The article analyzes why the I-168 submarine stood out while also reviewing its roles in supporting Japan during the war.

Design and Construction: A Technological Achievement and Strategic Asset

Japan's ambitious naval program in the interwar period resulted in the creation of the Kaidai-class submarine I-168 which was originally designated I-68 and belonged to the KD6A sub-class. The submarine's design as a long-range cruiser demonstrated Japan’s dedication to advancing underwater naval technology to support fleet maneuvers and execute independent enemy shipping attacks. The Kure Naval Arsenal began construction of the I-168 submarine on June 18, 1931 before launching her on June 26, 1933 and finally commissioning the vessel on July 31, 1934. The I-168 design showcased Japan’s dedication to building submarines that could traverse large expanses of the Pacific theater while sustaining high speed and combat effectiveness.

The I-168 represented an advanced development of Japanese submarine models based on World War I German U-boat technology. Within the Kaidai VIa series the submarine displayed enhanced speed capabilities alongside extended operational range and greater versatility compared to earlier models. The submarine extended 323 feet long with 27 feet beam width and 15 feet draft while displacing 1,785 tons when surfaced and 2,440 tons when submerged. The submarine operated on twin Kampon diesel engines which produced 4,500 horsepower for surface travel while utilizing two electric motors that generated 900 horsepower for submerged operations. The propulsion system enabled the I-168 to reach speeds up to 23 knots at the surface which made it one of the fastest submarines globally at that time and allowed it to travel at 8.25 knots while submerged.

The I-168 stood out because of its remarkable operating range. The I-168 could sustain surface travel of 14,000 nautical miles at 10 knots which enabled it to operate independently from Japanese waters for extended durations without needing resupply. The extended operational range of this submarine became vital for Japanese naval tactics which depended on submarines for reconnaissance activities and offensive missions across the Pacific Ocean.

The submarine’s armament was equally impressive. The submarine had six torpedo tubes with four located in the front and two at the rear which could hold up to 14 torpedoes in total. The I-168 became a powerful weapon in naval battles and surprise operations through its precision torpedo design for enemy ship attacks. The I-168 could fire surface targets with its 10 cm/50 Type 88 deck gun while defending against aircraft using the 13.2 mm anti-aircraft machine gun. The I-168's armament enabled it to perform both reconnaissance operations and direct combat duties competently.

The design also emphasized durability and survivability. The submarine had a maximum diving rating of 240 feet or 73 meters which enabled it to avoid enemy depth charges through evasive maneuvers. The submarine’s tough hull design allowed it to endure substantial damage and remain operational which became essential during its renowned mission at Midway where it resisted continuous depth charge assaults.

The I-168 distinguished itself through its unique combination of stealth capabilities and powerful armament. The Japan cruiser submarine class included this vessel which was built to engage enemy ships as well as conduct reconnaissance and support logistical functions throughout large-scale naval campaigns. The Japanese submarine fleet’s strategic importance was demonstrated through its reconnaissance operations before significant battles like Pearl Harbor.

During the era of the Kaidai VIa series submarines emerged as essential components for maintaining naval dominance throughout the world’s oceans. Japan designed the I-168 submarine to fulfill their view that submarines could deliver critical results in offensive and defensive military operations during war. This submarine showed exceptional capabilities because of its speed and range combined with firepower and strength which positioned it among Japan’s premier submarines when World War II began.

The I-168 achieved new standards for submarine design through its speed and operational range before it entered service in 1934. The incremental improvements of subsequent Japanese submarine classes demonstrated how the Kaidai VIa series represented advanced engineering for its period. Japanese naval engineering underwent significant transformation with the building of the I-168 which set the standards for submarine designs during World War II.

During the period between the late 1930s and early 1940s Japan's submarines including the I-168 rose in strategic importance within their military operations across the Pacific. Submarines provided essential support to Japan during the Midway and Guadalcanal campaigns through their capabilities to perform long-range patrols and strike important targets while remaining undetected. The design of the I-168 allowed it to perform its intended roles successfully while responding to changing naval warfare strategies.

The I-168 served as a strategic asset and technological accomplishment demonstrating Japan's submarine warfare strategy throughout World War II. The I-168’s innovative design merged speed with range and firepower and durability to create a versatile platform that affected major naval battles throughout multiple theaters. This submarine was Japan’s most advanced at commissioning time and established a benchmark for underwater combat which persisted throughout its World War II career.

What Made the I-168 Special?

The importance of the I-168 submarine extends beyond its design and includes its operational accomplishments throughout World War II. The Kaidai-class submarine was a demonstration of Japan’s dedication to developing advanced submarines for fleet operations support and independent enemy shipping attacks. The I-168 possessed speed and range capabilities along with powerful weapons systems which made it stand out among Japanese fleet submarines.

The I-168 stood out for its capability to perform covert reconnaissance missions while delivering effective attacks on key enemy targets. The submarine I-168 achieved its most notable mission during the Battle of Midway in June 1942 when it destroyed the damaged aircraft carrier USS *Yorktown* as well as the destroyer USS *Hammann*. The I-168 submarine's successful attack during the Battle of Midway represented one of the few Japanese victories in a battle that resulted in disaster for the Imperial Japanese Navy.

The I-168 exhibited extraordinary resistance to pressure during its operations. The submarine successfully navigated through the patrol of six U.S. destroyers to reach its target while undetected and launched four torpedoes upon approaching the *Yorktown* from a close distance. The submarine achieved its objectives before surviving a thirteen-hour depth charge counterattack from which it emerged with heavy damage.

Besides its combat functions the I-168 was crucial for logistical operations during the Guadalcanal and Aleutian Islands campaigns. The I-168 proved that it was more than just an attack submarine because it could deliver supplies and personnel through dangerous conditions.

Key role during World War II battles

Pearl Harbor Reconnaissance (December 1941)

The submarine I-168 operated under its pre-renaming designation I-68 to perform reconnaissance off Hawaii before Japan launched its unexpected attack on Pearl Harbor as part of Submarine Squadron Three. The submarine operated to collect U.S. naval intelligence and support Japan’s carrier strike force. Despite remaining passive in this operation Japan demonstrated its dependence on submarine reconnaissance for pre-battle intelligence through its deployment.

The Battle of Midway (June 1942)

The submarine I-168 reached the height of its wartime success during the Battle of Midway. Lieutenant Commander Yahachi Tanabe directed the submarine to seek out and attack damaged American vessels following Japan’s significant carrier losses at this battle.

The I-168 submarine executed a complex stealth operation through a destroyer screen to attack USS *Yorktown* before firing four torpedoes at a distance of 1,900 yards on June 6, 1942. The torpedo strike on USS *Hammann* led to rapid sinking because of underwater depth charges which killed many crew members attempting to escape. The Japanese submarine I-168 launched two torpedoes at *Yorktown*, which had been weakened by previous air attacks from Japanese bombers during the battle. The USS *Yorktown* stayed afloat briefly after the attack but ultimately sank at dawn on June 7.

The I-168 became one of just two Japanese submarines to engage enemy forces at Midway which established its status as Japan’s most successful submarine.

Guadalcanal Campaign (1942–1943)

The Japanese submarine I-168 began participating in supply missions for Japan’s Guadalcanal campaign after completing its repairs following the Battle of Midway. The submarine delivered ammunition and essential supplies to Japanese forces under siege while avoiding detection by Allied patrols around Guadalcanal. Supply missions during this critical period supported Japanese wartime operations but submarines such as I-168 faced serious dangers from Allied air and naval forces.

Aleutian Islands Campaign (1943)

During the Aleutian Islands campaign in early 1943 the submarine I-168 delivered ammunition and supplies to Japanese garrisons isolated on Attu and Kiska islands. The submarine completed multiple missions under difficult weather and persistent threats from U.S. submarines before needing maintenance in Japan.

The Final Mission: Sinking in Steffen Strait

The Japanese submarine I-168 was sunk on July 27, 1943 while conducting patrol operations near New Hanover Island in Steffen Strait. The submarine made an attack on USS *Scamp* but missed their target with its torpedoes. *Scamp* launched a counterattack by firing four torpedoes at periscope depth and reported that it had successfully sunk the Japanese submarine.

The destruction of I-168 represented a major setback for Japan's submarine fleet while highlighting the unit's operational capabilities as well as its weaknesses against Allied forces.

Legacy: A Symbol of Tactical Excellence

During World War II the **I-168** submarine gained fame for its remarkable operations at Midway and significant roles in other major Pacific battles. The I-168's sinking of USS *Yorktown* represented Japan's singular significant tactical success during that war period despite facing widespread strategic failures.

As a Kaidai-class submarine from Japan this vessel demonstrated technological advancements and demonstrated how submarines could affect naval battles through reconnaissance missions, logistical support tasks and direct combat engagements. The Japanese naval approach emphasized major fleet battles instead of focusing on anti-shipping missions and convoy attacks—areas where Allied submarines performed best—which limited the effectiveness of submarines such as I-168 within Japan's naval operations.

Although the wreck of **I-168** remains undiscovered historians remember its historical accounts which illustrate the naval warfare innovations and strategic lessons from World War II alongside victories achieved under difficult circumstances.