|I-25, which bombed the continental United States|
With the experience of World War I, the Germans and Italians knew that the most effective way to use submarines was to focus primarily on the enemy merchant fleet and in this, as shown above, they performed extremely well. The Imperial Japanese Navy, on the other hand, was intent on using their submarines primarily against enemy warships and incorporated them into their plan for a climactic naval battle that would settle everything with one blow. This is often attributed to the great Japanese victory over the Russians at the Battle of Tsushima in which the entire Russian fleet was totally pulverized by the Japanese ships under the great Admiral Togo. Japan hoped to repeat this same success against the United States, unfortunately, the Americans refused to play by Japanese rules and that great clash of fleets, for which Japan had been saving her best ships, including the largest battleships in the world, never happened. The U.S. Navy fought at a distance mostly with airpower while most American battleships were only ever used to shell island fortifications. The United States also used its own submarines extensively against Japanese merchant vessels, effectively wiping out the entire Japanese merchant marine by the time it was all over. They too scored victories against Japanese warships, no greater success being the sinking of the Japanese super-carrier Shinano (largest warship in the world) by the American submarine USS Archerfish.
|I-58, which sank the cruiser USS Indianapolis|
Those “other duties” usually involved acting as cargo carriers themselves, taking supplies to beleaguered Japanese forces defending islands in the South Pacific. This is both understandable and tragic. It is understandable because the situation was desperate and any way to get any supplies to these forces in the face of American air and naval superiority over the combat zone had to be looked at. The suffering that Japanese soldiers and sailors on these islands, especially Guadalcanal, was so immense as to defy description. Wracked by starvation, exhaustion and tropical diseases, as long as the poor soldiers were not evacuated, it is understandable that any means of getting supplies to them had to be considered. However, it is tragic because they simply should have been evacuated at that point as submarines are simply not effective cargo vessels. They amount of supplies they could possibly carry would necessarily be quite small and this prevented the subs from doing their real job which was sinking enemy ships, a job they were quite good at when given the chance. Subs were also detailed to undertake operations such as shelling the U.S. coast or dropping incendiary bombs in the hopes of sparking massive forest fires which, even if successful, would not have had any major impact on the war and, again, diverted them away from what they were best suited for.
At the outset of the war the biggest advantage Japanese submarines possessed was the Type 95 torpedo which had a very long range (up to 13,100 yards), packed a powerful punch and which ran on oxygen rather than compressed air which meant that it left no tell-tale trail of bubbles behind it, making it much harder to spot by surface ships before it was too late. In comparison, at the beginning of the war, the standard American torpedo was a complete disaster that frequently failed to hit its target, often failed to detonate when it did and sometimes posed a greater threat to the boat that fired it rather than the enemy. The Japanese naval technicians were also constantly working to improve their boats. The Kaidai 6 a/b type, produced in 1934-38, had the fastest surface speed of any sub in the world at 23 knots. The AM Type boats were built to carry attack aircraft and supplement the famous SenToku class boats and had the potential to be quite effective. However, only four were ordered and only two were actually completed before the high command ordered production halted to focus on smaller subs for the defense of Japan.
|The gigantic SenToku-class submarine aircraft carrier|
Certainly there are two types of submarines produced by Japan which most illustrate the great potential that the Imperial Japanese Navy had for submarine warfare if only it had been properly utilized. The first is the most well known, the aforementioned SenToku class which was the largest submarine type ever built and would retain that status all the way until 1965 with the launching of the U.S. nuclear ballistic missile submarine USS Benjamin Franklin. These were huge boats built to be, essentially, submarine aircraft carriers to launch surprise air attacks on extremely distant targets that would never be expected. Their design was highly innovative and a brilliant example of the creativity of Japanese naval engineers. Each could carry two small Seiran bomber aircraft as well as sufficient parts to be used to either repair the other two or put together for a third plane. The subs were coated with a special material, passed along from Germany, to make them more resistant to underwater search gear, special equipment was developed to allow for the aircraft to be prepared for flight while the boat was still submerged so that the boat could surface, launch its aircraft and submerge again as quickly as possible to avoid detection. These boats also had the longest range of any submarine ever developed and would hold that record until the development of the first nuclear submarines by the United States. Even today, there has never been a conventional submarine with a longer range than the Japanese SenToku class.
|The 'super sub' I-401|
The other class of submarine produced by Japan, which highlights Japanese submarine innovation and unrealized potential is less well known but deserves to be celebrated. This was the SenTaka class of which three boats were completed before the end of the war, I-201, I-202 and I-203. In terms of their design, these boats were years ahead of their time and were precursors of the design changes in submarine hulls that would most come to be associated with the age of nuclear submarines. These boats had anything that could cause drag either removed or made retractable so that they were extremely streamlined, making them much faster and more maneuverable underwater than anything the Allies had. The electric motors were twice as powerful as the diesel engines and they were equipped with high-capacity batteries that allowed for huge bursts of speed so that these boats were capable of achieving speeds of over 21 knots while submerged, something unheard of at the time. No other submarine in the world could go so fast underwater as the SenTaka class and they were also fitted with a snorkel so that they could recharge their batteries without having to surface. As a result, though they were small boats with a rather short range, they could conceivably have operated entirely submerged for the duration of their patrol which would have made them almost impossible to detect until they started sinking Allied ships. With four forward tubs and ten torpedoes with two deck guns they also packed a respectable punch for such a small boat.
|The highly advanced HA-201|
Finally, if all of this seems rather depressing for submarine enthusiasts, we have to keep a few things in mind. For one, the submarine force was not alone in being robbed of the chance to achieve its greatest glory. Japan famously produced the largest battleships in the world, saved for the hoped for decisive fleet battle with the United States, and none were ever able to really show what they could do in a ship-to-ship shooting match before they were sunk. It should probably also be mentioned that, like the Americans, the Japanese had little to no submarine combat experience before World War II. That does make a difference as we can clearly see what the German U-boats were able to achieve under the command of Admiral Karl Doenitz who was a veteran submarine commander who saw action in World War I as captain of UB-68. Even for the United States, while lacking the combat experience that the Germans had from World War I, it made a difference that the American naval commander in the Pacific was Admiral Chester Nimitz who, as a young officer, had commanded the USS Skipjack and held numerous submarine flotilla commands prior to World War II. He may have lacked combat experience but he certainly knew and appreciated what submarines were capable of and used them to best effect.
|I-58 carrying Kaiten 'human torpedoes'|